Bibliothek

X
feed icon rss

Ihre E-Mail wurde erfolgreich gesendet. Bitte prüfen Sie Ihren Maileingang.

Leider ist ein Fehler beim E-Mail-Versand aufgetreten. Bitte versuchen Sie es erneut.

Vorgang fortführen?

Exportieren
Filter
  • 1995-1999  (1.667)
  • 1985-1989  (638)
  • 1980-1984
  • 1965-1969  (822)
  • 1945-1949
  • 1930-1934
  • 1925-1929
  • 1920-1924
  • 1800-1809
  • 1996  (1.667)
  • 1987  (638)
  • 1969  (468)
  • 1966  (354)
  • 1945
  • 1931
  • 1929
  • 1926
  • Biochemistry and Biotechnology  (1.920)
  • Industrial Chemistry  (1.123)
  • Cat
Datenquelle
Materialart
Erscheinungszeitraum
  • 1995-1999  (1.667)
  • 1985-1989  (638)
  • 1980-1984
  • 1965-1969  (822)
  • 1945-1949
    • +
Jahr
Schlagwörter
  • 1
    Digitale Medien
    Digitale Medien
    Firing rhythmicity in the neocortex in vivo and in vitro under sustained iontophoretic excitation (1996)
    Springer
    Journal of comparative physiology 178 (1996), S. 63-74 
    Details
    ISSN: 1432-1351
    Schlagwort(e): Spike train ; Autocorrelation analysis ; Background and spontaneous firing ; Cat ; Guinea-pig
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Extracellular recordings were made from the cat intact neocortex and guinea-pig neocortical slices during microiontophoretic application of amino acid neurotransmitters. Spike train autocorrelation analysis showed a high stability of firing patterns in the intact neocortex. When excitation of a cell was increased in a step-wise manner with glutamate iontophoresis only an enhancement of the rate of firing was observed. The rhythmic component, which was mainly due to periodic multiple discharges, remained up to the highest firing frequencies. In contrast to the in vivo observation, glutamate, aspartate or K+ iontophoresis in cortical slices resulted in firing pattern alternations (always from bursts or irregular activity to regular spike firing) as well as an increase in firing rate. In slices the periodic component was typically due to single-spike regularity and its frequency rose with an increase of firing rate. The comparison of autocorrelogram alternations in vivo and in vitro suggests that the temporal organization of spike trains in the intact cortex is under tight external control and is defined mainly by neuronal interactions, whereas virtually all the neurons in vitro are very sensitive to the same iontophoretic influences and their individual outputs easily change according to the excitation (depolarization) level. The coincidence of the lowest frequencies of single-spike regularity in the in vitro preparation (5–7 Hz and 8–10 Hz) with theta- and alpha-rhythms in the electroencephalogram (EEG), and with single unit firing rhythmicity in the whole brain, may represent the basis of a unit-circuit resonance and provide a high stability of these EEG-rhythms.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00189591
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 2
    Digitale Medien
    Digitale Medien
    Lipoprotein Metabolism in Dogs and Cats (1996)
    Springer
    Comparative clinical pathology 6 (1996), S. 17-23 
    Details
    ISSN: 1433-2981
    Schlagwort(e): Cat ; Dog ; Hyperlipidaemia ; Lipoproteins
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract High-density lipoproteins (HDL) are the predominant lipoproteins in plasma of dogs and cats and are the major cholesterol-carrying particles. Two HDL subfractions are identifiable in dog: small, dense particles (equivalent to human HDL3) and large, buoyant particles called HDL1, which overlap in hydrated density with low-density lipoproteins (LDL). The HDL1 are enriched in cholesterol and apolipoprotein (apo) E, and are prevalent in dogs fed high amounts of cholesterol and, or, saturated fat, when they are also referred to as HDLc. Lipoproteins similar to human HDL2 and HDL3 are identifiable in feline plasma, along with trace HDL1. Lipoprotein lipase (LPL), hepatic lipase (HL) and lecithin: cholesterol acyl transferase (LCAT) activities are present in dogs and cats. Both species lack significant cholesteryl ester transfer protein activity, and reverse cholesterol transport is probably accomplished by receptor-mediated hepatic uptake of HDL1. Methods for the measurement of canine and feline plasma lipoprotein-cholesterol concentrations, apolipoprotein concentrations, and the activities of LPL, HL and LCAT have been developed. Together with oral and intravenous fat tolerance tests, these methods provide the basis for studying lipoprotein metabolism in cats and dogs.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00368097
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 3
    Digitale Medien
    Digitale Medien
    Senile plaques in very aged cats (1996)
    Springer
    Acta neuropathologica 91 (1996), S. 437-439 
    Details
    ISSN: 1432-0533
    Schlagwort(e): Key words Amyloid β-protein ; Cat ; Senile plaque
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Senile plaques were found in the cerebral cortices of three very aged cats (more than 18 years old). The plaques consisted of a coarse assembly of silver staining-positive materials, and was morphologically different from the well-known classical, primitive, and diffuse plaques. Congophilic amyloid angiopathy was observed in a few cortical arterioles of the oldest cat (20 years old). The senile plaques and a few cortical blood vessels were immunopositive for amyloid β-protein (Aβ). Aβ-positive materials were also sparsely distributed in the cortical neuropil but did not form senile plaques there. These findings should help to clarify the development of senile plaques and the early stage of Aβ deposition.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004010050448
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 4
    Digitale Medien
    Digitale Medien
    On the mechanism of the post-activation depression of the H-reflex in human subjects (1996)
    Springer
    Experimental brain research 108 (1996), S. 450-462 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Spinal cord ; H-reflexes ; Ia afferents ; Reflex pathways ; Homosynaptic depression ; Human ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract It was demonstrated that the soleus H-reflex was depressed for more than 10 s following a preceding passive dorsiflexion of the ankle joint. This depression was caused by activation of large-diameter afferents with receptors located in the leg muscles, as an ischaemic block of large-diameter fibres just below the knee joint abolished the depression, whereas a similar block just proximal to the ankle joint was ineffective. The depression of the H-reflex was not caused by changes in motoneuronal excitability, as motor-evoked potentials by magnetic brain stimulation were not depressed by the same passive dorsiflexion. Therefore it was concluded that the long-lasting depression is due to mechanisms acting at presynaptic level. The transmission of the monosynaptic Ia excitation from the femoral nerve to soleus motoneurones was not depressed by the ankle dorsiflexion. The depression thus seems to be confined to those afferents that were activated by the conditioning dorsiflexion. In parallel experiments on decerebrate cats, more invasive methods have complemented the indirect techniques used in the experiments on human subjects. A similar long-lasting depression of triceps surae monosynaptic reflexes was evoked by a preceding conditioning stimulation of the triceps surae Ia afferents. This depression was accompanied by a reduction of the monosynaptic Ia excitatory postsynaptic potential recorded intracellularly in triceps surae motoneurones, but not by changes in the input resistance or membrane potential in the motoneurones. Stimulation of separate branches within the triceps surae nerve demonstrated that the depression is confined to those afferents that were activated by the conditioning stimulus. This long-lasting depression was not accompanied by a dorsal root potential. It is concluded that the long-lasting depression is probably caused by a presynaptic effect, but different from the “classical” GABAergic presynaptic inhibition which is widely distributed among afferent fibres and accompanied by dorsal root potentials. It is more probably related to the phenomenon of a reduced transmitter release from previously activated fibres, i.e. a homosynaptic post-activation depression. The consequences of this post-activation depression for the interpretation of results on spinal mechanisms during voluntary movements in man are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00227268
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 5
    Digitale Medien
    Digitale Medien
    Light and electron microscopic analysis of synaptic input from cortical area 17 to the lateral posterior nucleus in cats (1996)
    Springer
    Experimental brain research 109 (1996), S. 63-70 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Corticothalamic ; Thalamus ; Immunocytochemistry ; γ-aminobutyric acid ; Phaseolus vulgaris leucoagglutinin ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The morphology and synaptic organization of the corticothalamic (CT) fibres from area 17 were studied in the lateral posterior nucleus (LP) of the thalamus in cats. Injection of the anterograde tracer Phaseolus vulgaris leucoagglutinin (PHAL) into primary visual cortex labelled a band of CT fibres in the LP with terminal field confined to its lateral division “LP1”. PHAL-labelled CT axons in the LP1 gave rise to both en passant and terminal boutons. They usually established several synaptic contacts -often in complex glomerulus-like synaptic arrangements-with dendritic shafts of large diameter and presynaptic dendrites containing pleomorphic vesicles. Postsynaptic targets of the PHAL-labelled CT boutons were characterized by postembedding γ-aminobutyric acid (GABA) immunocytochemistry. It appeared that, in the LP1 of the cat, almost half (44.5%) of the postsynaptic dendrites to CT boutons from area 17 belonged to the GABA-immunopositive interneurons and the majority (41%) of these GABA-immunopositive dendrites were F2 terminals. These results indicate that the CT axons from the striate cortex in the LP of the cat, in addition to a direct excitatory action, exert a powerful feed-forward inhibition on the thalamic principal cells.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00228627
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 6
    Digitale Medien
    Digitale Medien
    Increased oxidative metabolism in middle suprasylvian cortex following removal of areas 17 and 18 from newborn cats (1996)
    Springer
    Experimental brain research 110 (1996), S. 335-346 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Brain damage ; Cortical development ; Cytochrome oxidase ; Extrastriate cortex ; Neural plasticity ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract We measured changes in metabolic activity in middle suprasylvian (MS) cortex of cats subjected to early or late removal of areas 17 and 18 to localize shifts in activity possibly indicative of regions within MS cortex that may receive expanded inputs and be involved in the sparing of some visual behaviors following early primary visual cortex damage. Cytochrome oxidase (CO) activity was measured in MS cortex of mature, intact cats and of others with areas 17 and 18 removed in adulthood (P180), or on postnatal day 28 (P28) or postnatal day 1 (P1). Not less than 9 months after the ablation, brain sections were prepared and reacted for the presence of CO. The density of CO reactivity in each of the six cortical layers in MS cortex was measured and standardized against densities from ventral periaqueductal gray or hypothalamus on the same section. Following lesions on P1, significant increases in CO activity occurred in deep layer III and in layer IV of the medial bank of the MS sulcus, including all of area PMLS and the posterior portion of AMLS. In contrast, there were no significant differences in the level of CO activity among P28, P180, or intact cats for any of the cortical layers, and all had lower levels than the P1 cats. This metabolic change provides an anatomical marker for localizing adjustments in MS cortex and can be linked to amplified projections into MS cortex from the thalamus (LPm and A and C laminae of the dorsal lateral geniculate nucleus) and ventral posterior suprasylvian cortex following P1 ablations. Furthermore, this neurochemical analysis implicates a distinct region of MS cortex as the cortical locus of some spared visual functions following early primary visual cortex damage.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00229134
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 7
    Digitale Medien
    Digitale Medien
    Response properties of relay cells in the A-laminae of the cat's dorsal lateral geniculate nucleus after saccades (1996)
    Springer
    Experimental brain research 110 (1996), S. 435-445 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Vision ; Lateral geniculate nucleus ; Saccadic eye movements ; Suppression ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Responses of relay cells in the A-laminae of the dorsal lateral geniculate nucleus (LGNd) during spontaneous saccades and saccade-like visual stimulation were extracellularly recorded in awake cats. Ninety-six out of 137 cells recorded (42 X and 54 Y cells) were responsive during spontaneous saccadic eye movements. All Y cells and 67% of the X cells responded with burst activity, i.e. with either one or two activity peaks during and after saccades. Thirty-three percent of the X cells were inhibited during saccades. Excitatory peaks occurred at mean latencies of 33 ms and 31 ms for X and Y cells, respectively. Comparable burst responses were obtained when retinal image shifts similar to those during saccades were induced by external saccade-like stimulus movements. However, the latencies of excitatory peak activity were significantly longer to external stimuli than to the onsets of saccades. This indicates the existence of an eye movement-related input which activates LGNd relay cells in addition to the visual input. We propose that the pretectogeniculate projection may contribute to the responses of LGNd relay cells following saccadic eye movements via a disinhibitory input and that this input could be involved in intra- and postsaccadic modulations of the transfer of visual signals to visual cortex.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00229143
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 8
    Digitale Medien
    Digitale Medien
    Spatial coordination by descending vestibular signals (1996)
    Springer
    Experimental brain research 108 (1996), S. 85-100 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Vestibulospinal reflexes ; Medial vestibulospinal tract neurons ; Lateral vestibulospinal tract neurons ; Semicircular canal convergence ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Spatial response properties of medial (MVST) and lateral (LVST) vestibulospinal tract neurons were studied in alert and decerebrate cats during sinusoidal angular rotations of the whole body in the horizontal and many vertical planes. Of 220 vestibulospinal neurons with activity modulated during 0.5-Hz sinusoidal rotations, 200 neurons exhibited response gains that varied as a cosine function of stimulus orientation and phases that were near head velocity for rotation planes far from the minimum response plane. A maximum activation direction vector (MAD), which represents the axis and direction of rotation that maximally excites the neuron, was calculated for these neurons. Spatial properties of secondary MVST neurons in alert and decerebrate animals were similar. The responses of 88 of 134 neurons (66%) could be accounted for by input from one semicircular canal pair. Of these, 84 had responses consistent with excitation from the ipsilateral canal of the pair (13 horizontal, 27 anterior, 44 posterior) and 4 with excitation from the contralateral horizontal canal. The responses of the remaining 46 (34%) neurons suggested convergent inputs. The activity of 38 of these was significantly modulated by both horizontal and vertical rotations. Twelve neurons (9%) had responses that were consistent with input from both vertical canal pairs, including 9 cells with MADs near the roll axis. Thirty-two secondary MVST neurons (24%) had type II yaw and/or roll responses. The spatial response properties of 18 secondary LVST neurons, all studied in decerebrate animals, were different from those of secondary MVST neurons. Sixteen neurons (89%) had type II yaw and/or roll responses, and 12 (67%) appeared to receive convergent canal pair input. Convergent input was more common on higher-order vestibulospinal neurons than on secondary neurons. These results suggest that MVST and LVST neurons and previously reported vestibulo-ocular neurons transmit functionally different signals. LVST neurons, particularly those with MADs close to the roll axis, may be involved in the vestibular-limb reflex. The combination of vertical and ipsilateral horizontal canal input on many secondary MVST neurons suggests a contribution to the vestibulocollic reflex. However, in contrast to most neck muscles, very few neurons had maximum vertical responses near pitch.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00242906
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 9
    Digitale Medien
    Digitale Medien
    Responses of medullary reticulospinal neurones to stimulation of cutaneous limb nerves during locomotion in intact cats (1996)
    Springer
    Experimental brain research 111 (1996), S. 153-168 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Locomotion ; Reticulospinal neurones ; Cutaneous afferents ; Gating ; Postural control ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The present study was designed to determine whether the transmission of cutaneous afferent information from the limbs to the medullary reticular formation is phasically modulated during locomotion. Experiments were carried out in three chronically prepared, intact cats in which nerve cuff electrodes were placed, bilaterally, on the superficial radial and the superficial peroneal nerves. Thirty-seven reticulospinal neurones (RSNs) were identified by stimulation of their axons in the lumbar spinal cord (L2); 29 of 37 of these were recorded with the cat at rest, 28 of 37 during locomotion and 20 of 37 both at rest and during locomotion. Low-threshold stimulation of the cutaneous nerves evoked excitatory responses in the majority of RSNs both at rest and during locomotion. In the 28 of 37 RSNs recorded during locomotion, it was possible to record the evoked response to stimulation of all four limb nerves, giving a total of 184 tested cases [RSNs testedxnumber of nerves stimulatedxphase of stimulation (swing or stance)]. The responses of most RSNs to cutaneous stimulation were modulated in a phase-dependent manner during locomotion. The maximal responses in most, but not all, cases were obtained during the swing phase of the limb that was stimulated and were largely independent of the discharge pattern of the cell. We interpret this result as indicating that the efficacy of transmission of the afferent information is determined more by the excitability of the spinal relay neurones than by the level of excitability of the RSNs in the brainstem. It is suggested that the base discharge pattern of RSNs might be largely determined by their central afferent input, while peripheral afferent inputs would primarily serve to modify the RSN discharge pattern in response to perturbations.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00227294
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 10
    Digitale Medien
    Digitale Medien
    Segmental and supraspinal control of synaptic effectiveness of functionally identified muscle afferents in the cat (1996)
    Springer
    Experimental brain research 107 (1996), S. 391-404 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Primary afferent depolarization ; Presynaptic inhibition ; Muscle afferents ; Spinal cord ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The present investigation documents the patterns of primary afferent depolarization (PAD) of single, functionally identified muscle afferents from the medial gastrocnemius nerve in the intact, anesthetized cat. Classification of the impaled muscle afferents as from muscle spindles or from tendon organs was made according to several criteria, which comprised measurement of conduction velocity and electrical threshold of the peripheral axons, and the maximal frequency followed by the afferent fibers during vibration, as well as the changes in discharge frequency during longitudinal stretch, the projection of the afferent fiber to the motor pool, and, in unparalyzed preparations, the changes in afferent activity during a muscle twitch. In confirmation of a previous study, we found that most muscle spindle afferents (46.1–66.6%, depending on the combination of criteria utilized for receptor classification) had a type A PAD pattern. That is, they were depolarized by stimulation of group I fibers of the posterior biceps and semitendinosus (PBSt) nerve, but not by stimulation of cutaneous nerves (sural and superficial peroneus) or the bulbar reticular formation (RF), which in many cases inhibited the PBSt-induced PAD. In addition, we found a significant fraction of muscle spindle primaries that were depolarized by stimulation of group I PBSt fibers and also by stimulation of the bulbar RF. Stimulation of cutaneous nerves produced PAD in 9.1–31.2% of these fibers (type B PAD pattern) and no PAD in 8.2–15.4% (type C PAD pattern). In contrast to muscle spindle afferents, only the 7.7–15.4% of fibers from tendon organs had a type A PAD pattern, 23–46.1% had a type B and 50–61.5% a type C PAD pattern. These observations suggest that the neuronal circuitry involved in the control of the synaptic effectiveness of muscle spindles and tendon organs is subjected to excitatory as well as to inhibitory influences from cutaneous and reticulospinal fibers. As shown in the accompanying paper, the balance between excitation and inhibition is not fixed, but can be changed by crushing the afferent axons in the peripheral nerve and allowing subsequent reconnection of these afferent fibers with muscle receptors.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00230421
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 11
    Digitale Medien
    Digitale Medien
    Differential spinal projections from the forelimb areas of the rostral and caudal subregions of primary motor cortex in the cat (1996)
    Springer
    Experimental brain research 108 (1996), S. 191-205 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Spinal cord ; Dorsal horn ; Ventral horn ; Intermediate zone ; Propriospinal neurons ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract We used anterograde transport of WGA-HRP to examine the topography of corticospinal projections from the forelimb areas within the rostral and caudal motor cortex subregions in the cat. We compared the pattern of these projections with those from the somatic sensory cortex. The principal finding of this study was that the laminar distribution of projections to the contralateral gray matter from the two motor cortex subregions was different. The rostral motor cortex projected preferentially to laminae VI–VIII, whereas caudal motor cortex projected primarily to laminae IV–VI. Confirming earlier findings, somatic sensory cortex projected predominantly to laminae I–VI inclusive. We found that only rostral motor cortex projected to territories in the rostral cervical cord containing propriospinal neurons of cervical spinal segments C3-4 and, in the cervical enlargement, to portions presumed to contain Ia inhibitory interneurons. We generated contour maps of labeling probability on averaged segmental distributions of anterograde labeling for all analyzed sections using the same algorithm. For rostral motor cortex, heaviest label in the dorsal part of lamina VII in the contralateral cord was consistently located in separate medial and lateral zones. In contrast, no consistent differences in the mediolateral location of label was noted for caudal motor cortex. To summarize, laminae I–III received input only from the somatic sensory cortex, while laminae IV–V received input from both somatic sensory and caudal motor cortex. Lamina VI received input from all cortical fields examined. Laminae VII–IX received input selectively from the rostral motor cortex. For motor cortex, our findings suggest that projections from the two subregions comprise separate descending pathways that could play distinct functional roles in movement control and sensorimotor integration.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00228094
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 12
    Digitale Medien
    Digitale Medien
    Activity of neurons of the subthalamic nucleus in relation to motor performance in the cat (1996)
    Springer
    Experimental brain research 108 (1996), S. 206-220 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Subthalamic nucleus ; Pallidum ; Motor initiation ; Single-unit activity ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The activity of subthalamic nucleus neurons related to motor performance was studied in three unrestrained cats operantly conditioned to perform a lever-release movement. The movement was initiated either rapidly after the trigger stimulus (a brief sound) in a simple reaction-time paradigm or after a delay in trials identified by a tone cue. These paradigms were randomly presented. The activity of 171 neurons was recorded in the contralateral and in the ipsilateral subthalamic nucleus, with respect to the performing limb. The mean spontaneous activity of cells in the ipsilateral side (18.5±13.8 imp/s, mean±SD) was higher than that in the contralateral side (8.5±8.1 imp/s). A total of 145 cells (85%) presented significant changes in activity in relation to the lever-release movement (task-related cells). The remaining 26 cells were either related to other events of the task (n=15; lever-press or reinforcement occurrence) or not related at all to the task performance (n=11). The majority of changes of activity of task-related cells were initial increases in discharge, which started on average, 127 ms before movement onset and lasted several hundreds of milliseconds. These increases in discharge were more frequent in the contralateral side (75 of 80 task-related cells, 94%) than in the ipsilateral side (43 of 65 task-related cells, 66%). The changes in activity, either increases or decreases, occurred early after the trigger stimulus, since 62% of them had a latency of less than 100 ms. Although the mean latency of initial increases was rather similar in both sides (97 ms contralateral versus 104 ms ipsilateral), the contralateral side was characterized by a high proportion of very early responses (less than 20 ms). For most neurons, the early changes in activity described above were absent after the trigger stimulus in the delayed condition. For certain neurons, the changes in activity prior to movement were different in reactiontime condition and in delayed condition, showing that the pattern of activity preceding movement might depend on the temporal requirements for motor initiation. The results suggest that a significant proportion of subthalamic cells are involved in the preparation and the initiation phases of the lever-release movement studied, although other hypotheses (e.g. stimulus-related responses) cannot be definitely ruled out. The timings and patterns of the changes in activity observed in the subthalamic nucleus in the present study, and in the pallidal complex previously, cannot be explained easily by the classical scheme where the external pallidum inhibits the subthalamic nucleus. The results suggest rather that the subthalamic nucleus, driven by a yet-to-be-determined excitatory input, exerts an excitatory influence on the pallidum and plays a crucial role in the control of the basal ganglia output neurons.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00228095
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 13
    Digitale Medien
    Digitale Medien
    Binocular interactions and disparity coding in area 21a of cat extrastriate visual cortex (1996)
    Springer
    Experimental brain research 108 (1996), S. 257-272 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Binocular positional disparities ; Orientation selectivity ; Binocular summation and facilitation ; Depth discrimination ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract We have examined, using both qualitative and quantitative techniques, binocular interactions of extracellularly recorded single neurons in the extrastriate cortical area 21a of anaesthetized and paralysed cats. Consistent with previous reports we have found that: (a) all area 21a neurons were orientation-selective, with about 65% of them preferring orientations within 30° of the vertical; and (b) over 75% of area 21a cells could be activated through either eye. Furthermore, a significant minority (4 cells; about 10%) of a subpopulation of 39 neurons in which binocular interactions were examined quantitatively, were “obligatory binocular neurons”, that is, they responded very weakly, if at all, to the monocular stimuli presented through either eye but responded vigorously to simultaneous stimulation through both eyes. Almost 70% (27/39) of neurons tested quantitatively for binocular interaction have shown significant modulation (over 50%) of their peak responses in relation to binocular positional retinal disparities. The majority of neurons sensitive to binocular positional disparities resembled either “tuned excitatory” (22 cells; 56.5% of the sample) or “tuned inhibitory” (2 cells; 5% of our sample) cells. In particular, they gave, respectively, maximal or minimal responses to optimally oriented, moving photic stimuli when the receptive fields plotted through each eye completely or partially overlapped. Although neurons recorded in area 21a have relatively large receptive fields (mean width 3.3±1.1°; range 2.0–5.6°), the mean width of the disparity tuning curve (2.8±1.0°; range 1.3–4.8°) for our sample of area 21a neurons was similar to those of neurons with significantly smaller receptive fields, recorded in areas 17 and 18 of cat's primary visual cortex. We conclude that area 21a of the cat, like areas 17 and 18 of primary visual cortex, is likely to play an important role in binocular depth discrimination and might constitute a “higher order” area for stereoscopic binocular vision.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00228099
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 14
    Digitale Medien
    Digitale Medien
    Simulation of dynamic fusimotor effects in the discharge frequency of la afferents by prestretching the muscle spindle (1996)
    Springer
    Experimental brain research 108 (1996), S. 297-304 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Dynamic γ stimulation ; Bag,1 Ia afferents ; Discharge pattern regularity ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The discharge patterns of primary muscle spindle afferents from the tibial anterior muscle of the cat were recorded under a ramp-and-hold stretch of constant amplitude (7 mm) and stretch rates varying between 1 and 50 mm/s. With seven Ia fibers, the discharge patterns were recorded under various dynamic γ stimulation frequencies of between 10 and 120 stimuli per second. With 26 passive spindle fibers of the type known as bag1 Ia fibers, the discharge patterns were obtained under progressively increasing prestretch of the muscle. From each discharge pattern the following discharge frequencies were read: the initial activity (the discharge frequency before the start of ramp stretching), the peak dynamic discharge (the discharge frequency at the end of the dynamic phase of stretching), the maximum static value (MSt; the discharge frequency at the beginning of the static phase of stretching), and the final static value (the discharge frequency at the end of the 3rd s of the plateau phase). These four discharge frequency values were plotted against MSt, in separate diagrams for the Ia fibers under dynamic γ stimulation and for the bag1 Ia fibers. The relationship between the four discharge frequency values and the MSt turned out to be the same or much the same for both groups of Ia fibers. This means that the two groups of Ia fibers produced (more or less) identical discharge patterns in response to the ramp-and-hold stretch. In addition, where Ia fibers of the two groups had the same MSt, their dynamic and static responses were determined. Under these circumstances no difference was found in respect to their stretch properties between Ia fibers of dynamically γ-activated spindles and bag1 Ia fibers of passive spindles. In the Discussion, the high degree of similarity in the behavior of the two groups of Ia fibers is explained in terms of the mechanical properties of intrafusal bag1 fibers, which render it likely that in passive intrafusal bag1 fibers stretch activation will evoke the same mechanical behavior as dynamic γ activation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00228102
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 15
    Digitale Medien
    Digitale Medien
    Effect of tris-(hydroxymethyl)-aminomethane on experimental focal cerebral ischemia (1996)
    Springer
    Experimental brain research 111 (1996), S. 51-56 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Focal cerebral ischemia ; Cerebral acidosis ; Tris(hydroxymethyl)-aminomethane ; Brain edema ; Lactate ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Systemic and focal cerebral acidosis is considered deleterious to cell metabolism and neuronal recovery. We investigated the immediate effect of tris-(hyroxymethyl)-aminomethane (THAM), an alkalizing agent, on focal cerebral ischemia produced by occlusion of the left middle cerebral artery (MCA) in cats with systemic acidosis. Occlusion of MCA resulted in prompt decreases in local cerebral blood flow of the ipsilateral marginal and ectosylvian gyri from 47.7 ml/100 g per minute in control to 32.3 ml/100 g per minute and 8.3 ml/100 g per minute, respectively. In the control group, physiological saline was infused continuously and the treated group received 0.3 M THAM to normalize systemic and focal cerebral acidosis. There were no significant changes in the systemic arterial pressure, arterial PO2 and PCO2 throughout the experiments in the two groups. Arterial pH decreased from 7.42 to 7.30 in the control, while it remained normal during THAM treatment. Extracellular pH of the marginal gyrus (peri-infarct zone) decreased from 7.39 to 6.87 with 6 h ischemia in the control group. In THAM infusion, extracellular pH was kept between 7.26 and 7.29, which was significantly higher than the control group. THAM significantly decreased infarct volume and lactate and water contents of the gray matter in the marginal gyrus at 6 h after occlusion. It is concluded that THAM infusion immediately after ischemia onset is considered effective in improving acidosis at the site of ischemic penumbra and consequently reduces lactate production, brain edema, and infarct volume.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00229555
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 16
    Digitale Medien
    Digitale Medien
    Dorsal border periaqueductal gray neurons project to the area directly adjacent to the central canal ependyma of the C4-T8 spinal cord in the cat (1996)
    Springer
    Experimental brain research 112 (1996), S. 11-23 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Periaqueductal gray ; Spinal cord ; Central canal ; Hypothalamohypophysial ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract In a previous study horseradish peroxidase (HRP) injections in the upper thoracic and cervical spinal cord revealed some faintly labeled small neurons at the dorsal border of the periaqueductal gray (PAG). The present light microscopic and electronmicroscopic tracing study describes the precise location of these dorsal border PAG-spinal neurons and their terminal organization. Wheat germ agglutinin-conjugated HRP (WGA-HRP) injections into cervical and upper thoracic spinal segments resulted in several hundreds of small retrogradely labeled neurons at the dorsal border of the ipsilateral caudal PAG. These neurons were not found after injections in more caudal segments. WGA-HRP injections in the dorsal border PAG region surprisingly resulted in anterogradely labeled fibers terminating in the area dorsally and laterally adjoining the central canal ependyma of the C4-T8 spinal cord. No anterogradely labeled fibers were found more caudal in the spinal cord. The labeled fibers found in the upper cervical cord were not located in the area immediately adjoining the ependymal layer of the central canal, but in the lateral part of laminae VI, VII and VIII and in area X bilaterally. Electronmicroscopic results of one case show that the dorsal border PAG-spinal neurons terminate in the neuropil of the subependymal area and in the vicinity of the basal membranes of capillaries located laterally to the central canal. The terminal profiles contain electron-lucent and densecored vesicles, suggesting a heterogeneity of possible transmitters. A striking observation was the lack of synaptic contacts, suggesting nonsynaptic release from the profiles. The function of the dorsal border PAG-spinal projection is unknown, but considering the termination pattern of the dorsal border PAG neurons on the capillaries the intriguing similarity between this projection system and the hypothalamohypophysial system is discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00227173
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 17
    Digitale Medien
    Digitale Medien
    Smooth eye movements evoked by electrical stimulation of the cat's superior colliculus (1996)
    Springer
    Experimental brain research 107 (1996), S. 382-390 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Saccades ; Smooth eye movements ; Eye drifts ; Superior colliculus ; Cat ; Electrical stimulation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Head-fixed gaze shifts were evoked by electrical stimulation of the deeper layers of the cat superior colliculus (SC). After a short latency, saccades were triggered with kinematics similar to those of visually guided saccades. When electrical stimulation was maintained for more than 150–200 ms, postsaccadic smooth eye movements (SEMs) were observed. These movements were characterized by a period of approximately constant velocity following the evoked saccade. Depending on electrode position, a single saccade followed by a slow displacement or a “staircase” of saccades interspersed by SEMs were evoked. Mean velocity decreased with increasing deviation of the eye in the orbit in the direction of the movement. In the situation where a single evoked saccade was followed by a smooth movement, the duration of the latter depended on the duration of the stimulation train. In the situation where evoked saccades converged towards a restricted region of the visual field (“goal”-directed or craniocentric saccades), the SEMs were directed towards the centre of this region and their mean velocity decreased as the eye approached the goal. The direction of induced SEMs depended on the site of stimulation, as is the case for saccadic eye movements, and was not modified by stimulation parameters (“place” code). On the other hand, mean velocity of the movements depended on the site of stimulation and on the frequency and intensity of the current (“rate” code), as reported for saccades in the cat. The kinematics of these postsaccadic SEMs are similar to the kinematics of slow, postsaccadic correction observed during visually triggered gaze shifts of the alert cat. These results support the hypothesis that the SC is not exclusively implicated in the control of fast refixation of gaze but also in controlling postsaccadic conjugate slow eye movements in the cat.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00230420
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 18
    Digitale Medien
    Digitale Medien
    Changes in PAD patterns of group I muscle afferents after a peripheral nerve crush (1996)
    Springer
    Experimental brain research 107 (1996), S. 405-421 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Primary afferent depolarization ; Presynaptic inhibition ; Muscle afferents ; Nerve crush ; Spinal cord ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract In the anesthetized cat we have analyzed the changes in primary afferent depolarization (PAD) evoked in single muscle spindle and tendon organ afferents at different times after their axons were crushed in the periphery and allowed to regenerate. Medial gastrocnemius (MG) afferents were depolarized by stimulation of group I fibers in the posterior biceps and semitendinosus nerve (PBSt), as soon as 2 weeks after crushing their axons in the periphery, in some cases before they could be activated by physiological stimulation of muscle receptors. Two to twelve weeks after crushing the MG nerve, stimulation of the PBSt produced PAD in all MG fibers reconnected with presumed muscle spindles and tendon organs. The mean amplitude of the PAD elicited in afferent fibers reconnected with muscle spindles was increased relative to values obtained from Ia fibers in intact (control) preparations, but remained essentially the same in fibers reconnected with tendon organs. Quite unexpectedly, we found that, between 2 and 12 weeks after crushing the MG nerve, stimulation of the bulbar reticular formation (RF) produced PAD in most afferent fibers reconnected with muscle spindle afferents. The mean amplitude of the PAD elicited in these fibers was significantly increased relative to the PAD elicited in muscle spindle afferents from intact preparations (from 0.08–0.4 to 0.47-0.34 mV). A substantial recovery was observed between 6 months and 2.5 years after the peripheral nerve injury. Stimulation of the sural (SU) nerve produced practically no PAD in muscle spindles from intact preparations, and this remained so in those afferents reconnected with muscle spindles impaled 2–12 weeks after the nerve crush. The mean amplitude of the PAD produced in afferent fibers reconnected with tendon organs by stimulation of the PBSt nerve and of the bulbar RF remained essentially the same as the PAD elicited in intact afferents. However, SU nerve stimulation produced a larger PAD in afferents reconnected with tendon organs 2–12 weeks after the nerve crush (mean PAD changed from 0.05-0.04 to 0.32-0.17 mV). The results obtained indicate that the PAD patterns of the afferent fibers reconnected with muscle spindle and tendon organ afferents are changed after crushing their axons in the periphery: stimulation of the bulbar RF appears to produce larger PAD in fibers reconnected with muscle spindles, and stimulation of cutaneous afferents produces larger PAD in fibers reconnected with tendon organs. It is suggested that these alterations in the patterns of PAD of muscle afferents result from central changes in the balance of excitatory and inhibitory influences acting on the segmental pathways mediating the PAD. Although the functional role of these changes has not been established, they may reflect compensatory changes aimed to adjust information arising from damaged afferents.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00230422
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 19
    Digitale Medien
    Digitale Medien
    Convergence of skin reflex and corticospinal effects in segmental and propriospinal pathways to forelimb motoneurones in the cat (1996)
    Springer
    Experimental brain research 107 (1996), S. 422-434 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Forelimb motoneurones ; Cutaneous reflex ; Pyramidal tract ; Spinal cord ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The organization of facilitatory convergence from cutaneous afferents (Skin) and the corticospinal tract (pyramidal tract, Pyr) in pathways to forelimb motoneurones of mainly distal muscles was studied in anaesthetized cats by analysing postsynaptic potentials (PSPs), which were spatially facilitated by combinations of stimuli to the two sources at different time intervals. Conditioning Pyr volleys facilitated Skin-evoked PSPs of fixed (1.2–3.6 ms) central latencies (Skin PSPs), suggesting that disynaptic and polysynaptic skin reflex pathways are facilitated from the pyramidal tract. The shortest latencies (1.2–1.7 ms) of pyramidal facilitation suggested direct connection of pyramidal fibres with last order neurones of skin reflex pathways. Conditioning Skin volleys facilitated Pyr-evoked PSPs of fixed, mostly disynaptic latencies (1.0–2.5 ms; Pyr PSPs), suggesting that pyramido-motoneuronal pathways are facilitated from Skin at a premotoneuronal level. The shortest pathway from skin afferents to the premotor neurones appeared to be monosynaptic. Although Pyr and Skin volleys were mutually facilitating, the facilitation curve of Pyr PSPs and that of Skin PSPs were discontinuous to each other, with the peak facilitation at different Skin-Pyr volley intervals. Transection of the dorsal column (DC) at the C5/C6 border had little effect on the latencies or amplitudes evoked by maximal stimulation and the pyramidal facilitation of Skin PSPs. In contrast, the facilitation of Pyr PSPs by Skin stimulation was greatly decreased after the DC transection, and the facilitation curve of Pyr PSPs was continuous to that of Skin PSPs, with no separate peak. Latencies of Pyr PSPs ranged similarly to those in DC intact preparations. More rostral DC transection (C4/C5 border) reduced Skin-facilitated Pyr excitatory PSPs (EPSPs) less than C5/C6 lesions, suggesting that the C5 segment also contains neurones mediating Skin-facilitated Pyr EPSPs. The results show that convergence from skin afferents and the corticospinal tract occurs at premotor pathways of different cervical segments. We suggest that corticospinal facilitation of skin reflex occurs mostly in the brachial segments and Skin facilitation of cortico-motoneuronal effects takes place largely in the rostral cervical segments and partly in the brachial segments.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00230423
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 20
    Digitale Medien
    Digitale Medien
    Activity of dorsal respiratory group inspiratory neurons during laryngeal-induced fictive coughing and swallowing in decerebrate cats (1996)
    Springer
    Experimental brain research 108 (1996), S. 247-256 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Nucleus tractus solitarii ; Dorsal respiratory group ; Inspiratory neurons ; Superior laryngeal nerve ; Fictive coughing and swallowing ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Membrane potential changes and/or discharges from 36 inspiratory neurons were recorded intracellularly in the dorsal respiratory group (DRG; i.e., the ventrolateral subdivision of the nucleus tractus solitarii) in decerebrate, paralyzed, and ventilated cats. Electrical activities were recorded from both somata (n=10) and axons (n=26). Activities during quiet breathing were compared with those observed during fictive coughing and swallowing evoked by repetitive electrical stimulation of afferent fibers of the superior laryngeal nerve (SLN). These nonrespiratory behaviors were evident in paralyzed animals as characteristic discharge patterns of the phrenic, abdominal, and hypoglossal nerves. Twenty-six neurons exhibiting antidromic action potentials in response to electrical stimuli applied to the cervical (C3–5) spinal cord were classified as inspiratory bulbospinal neurons (IBSNs). These neurons were considered as premotoneurons. The remaining 10 inspiratory neurons (INAA) were not antidromically activated by electrical stimuli applied to either cervical spinal cord or ipsilateral cervical vagus. These neurons are thought to be propriobulbar neurons. We recorded the activity of 31 DRG inspiratory neurons (24 IBSNs and 7 I-NAA) during coughing. All but one (a late-recruited IBSN) discharged a burst of action potentials during the coughing-related phrenic nerve activity. Typically, ramp-like membrane depolarization trajectories and discharge frequencies during coughing were similar to those observed during inspiration. We recorded the activity of 33 DRG inspiratory neurons (23 IBSNs and 10 I-NAA) during swallowing. Most (28/33) neurons were briefly activated, i.e., discharged a burst of action potentials during swallowing, but peak discharge frequency decreased compared with that measured during inspiration. The membrane potentials of nine somata exhibited a brief bell-shaped depolarization during swallowing, the amplitude of which was similar to that observed during inspiration. These results suggest that some inspiratory premotoneurons and propriobulbar neurons of the DRG might be involved in nonrespiratory motor activities, even if clearly antagonistic to breathing (e.g., swallowing). We postulate the existence in the medulla oblongata of adult mammals of neurons exhibiting a “functional flexibility”.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00228098
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 21
    Digitale Medien
    Digitale Medien
    Firing properties of preposito-collicular neurones related to horizontal eye movements in the alert cat (1996)
    Springer
    Experimental brain research 110 (1996), S. 413-424 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Prepositus hypoglossi nucleus ; Superior colliculus ; Eye position ; Eye velocity ; Feedback control ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The projection from the nucleus prepositus hypoglossi (PH) to the superior colliculus (SC) has been proposed to provide a feedback control of collicular saccadic activities. The present study aimed to identify the functional properties of PH neurones projecting to the SC relative to eye movement parameters. Preposito-collicular neurones were identified in alert cats by antidromic invasion and collision tests following electrical stimulations of the contralateral SC. Their discharges were then correlated with the horizontal component of eye movements. Particular attention was given to the timing of discharges relative to saccade onsets. Most prepositocollicular neurones (12/14) displayed transient activities associated to eye velocity, and onsets preceded the saccade onset by 9.4–19.9 ms. The mean eye velocity sensitivity of these “early” preposito-collicular neurones (1.46±0.53 spikes/s per degree per second) was quite similar to that calculated from a sample of putative motoneurones or interneurones that have been recorded within abducens nucleus and quantified in the same conditions. The remaining two preposito-collicular neurones exhibited transient activity related to saccades, but this followed the transient putative motoneuronal discharge. These “delayed” neurones also had lower eye velocity sensitivities (0.38 sp/s per degree per second and 0.58 sp/s per degree per second, respectively) compared with early neurones. Both classes of preposito-collicular neurones also displayed a subsequent tonic activity correlated with the eye position. Taken together, these results demonstrate that preposito-collicular neurones code both eye position and eye velocity just like ocular motoneurones, but in a predictive manner. The anticipatory discharge of early neurones makes them likely candidates for the control of peak activities of saccade-related collicular neurones, particularly in the caudal colliculus. Delayed preposito-collicular neurones may also participate in the control of collicular activities, but probably in more rostral SC, where peak activities occur later during eye movements together with smaller motor error coding.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00229141
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 22
    Digitale Medien
    Digitale Medien
    Peripheral nerve stimulation increases fos immunoreactivity without affecting type II Ca2+/calmodulin-dependent protein kinase, glutamic acid decarboxylase, or GABAA receptor gene expression in cat spinal cord (1996)
    Springer
    Experimental brain research 111 (1996), S. 326-336 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Plasticity ; c-fos ; mRNAs ; Primary afferents ; In situ hybridization ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Expression patterns of the immediate early gene c-fos and of other genes including those for the α-subunit of type II Ca2+/calmodulin-dependent protein kinase (CaMKIIα), 67-kDa glutamic acid decarboxylase (GAD), and the α1-, β2-, and γ2-subunits of the GABAA receptor were described in the spinal cord of normal cats and following peripheral nerve stimulation. As revealed by in situ hybridization histochemistry, CaMKIIα messenger RNA (mRNA) is normally distributed only in cells of Rexed's laminae I–IV, whereas GAD mRNA is expressed by subpopulations of cells in all laminae, with the heaviest hybridization signal found in laminae I–III and medial parts of laminae V and VI. The three GABAA receptor subunits have varying expression patterns in the laminae. All of them are expressed by many cells located in the base of the dorsal horn and the intermediate zone, but only the γ2-subunit is intensely expressed by motoneurons. Single-pulse, electrical stimulation of the sciatic or median and ulnar nerves of anesthetized cats at a pulse rate of 1/s for 6–8 h failed to induce observable changes in gene expression for CaMKIIα, GAD, or for the three subunits of the GABAA receptor; although immunoreactivity for the protein products of c-fos (or c-fos-related genes) was markedly upregulated in some neurons of the dorsal horn and the intermediate zone. Therefore, under the present experimental conditions, upregulation of the immediate early gene c-fos (or c-fos-related genes) is not associated with changes in expression of late-effector genes potentially involved in central nervous system plasticity.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00228722
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 23
    Digitale Medien
    Digitale Medien
    Properties of utricular nerve-activated vestibulospinal neurons in cats (1996)
    Springer
    Experimental brain research 112 (1996), S. 197-202 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Utricular nerve ; Vestibulospinal neuron ; Lateral and medial vestibulospinal tracts ; Vestibular nuclei ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The axonal pathway, conduction velocities, and locations of the cell bodies of utricular nerve-activated vestibulospinal neurons were studied in decerebrated or anesthetized cats using the collision test of orthodromic and antidromic spikes. For orthodromic stimulation, bipolar tungsten electrodes were placed on the utricular nerve and the other vestibular nerve branches were transected. Monopolar tungsten electrodes were positioned on both sides of the upper cervical segments (C2–4), caudal end of the cervical enlargement (C7-T1), and from the lower thoracic to the upper lumbar segments (T12-L3) and were used for antidromic stimulation of the spinal cord. Another monopolar electrode was also placed in the oculomotor nucleus to study whether utricular nerve-activated vestibulospinal neurons have ascending branches to the oculomotor nucleus. Of the 173 vestibular neurons orthodromically activated by the stimulation of the utricular nerve, 46 were second-order vestibulospinal neurons and 5 were third-order neurons. The majority of the utricular nerve-activated vestibulospinal neurons were located in the rostral part of the descending vestibular nucleus and the caudal part of the ventral lateral nucleus. Seventy-three percent of the utricular nerve-activated vestibulospinal neurons descended through the ipsilateral lateral vestibulospinal tract. Approximately 80% of these neurons reached the cervicothoracic junction, but a few reached the upper lumbar spinal cord. Twenty-seven percent of the utricular nerve-activated vestibulospinal neurons descended through the medial vestibulospinal tract or the contralateral vestibulospinal tracts. Those axons terminated mainly in the upper cervical segments. Almost none of the utricular nerve-activated vestibular neurons had ascending branches to the oculomotor nucleus.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00227638
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 24
    Digitale Medien
    Digitale Medien
    Synaptic interactions of retrogradely labeled hypoglossal motoneurons with substance P-like immunoreactive nerve terminals in the cat: a dual-labeling electron microscopic study (1996)
    Springer
    Experimental brain research 110 (1996), S. 175-182 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Hypoglossal motoneurons ; Retrograde transport ; Synaptic interactions ; Substance P ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract This study has investigated the synaptic interactions between hypoglossal motoneurons and substance P (SP)-immunoreactive terminals. Cholera toxin B conjugated to horseradish peroxidase was injected into the tip of the tongue on the right side of six ketamine-anesthetized cats. Two to five days later, the animals were killed. Cells containing HRP were labeled with a histochemical reaction utilizing tetramethylbenzidine (TMB) as the chromogen. TMB forms crystalline reaction products that are very distinct at the electron microscopic level. The tissues were then processed for immunocytochemisty using an antiserum against SP. The chromogen used in this case, di-aminobenzidine, yields amorphous reaction products. At the light microscopic level, labeled cells were observed primarily ipsilaterally in both intermediate and ventrolateral subdivisions of the hypoglossal nucleus. The majority of these labeled cells were seen at the level of obex. At the electron microscopic level, both asymmetric and symmetric synapses were observed. SP-immunoreactive nerve terminals formed asymmetric synapses with labeled dendrites and symmetric synapses with labeled perikarya. SP-labeled terminals also synapsed on unlabeled dendrites and somata. These are the first ultrastructural studies demonstrating synaptic interactions between hypoglossal motoneurons and SP terminals. These studies demonstrate that hypoglossal motoneurons that innervate intrinsic tongue muscles are modulated by SP and that SP may play a role in the control of fine movements of the tongue.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00228549
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 25
    Digitale Medien
    Digitale Medien
    Neural connectivity only accounts for a small part of neural correlation in auditory cortex (1996)
    Springer
    Experimental brain research 110 (1996), S. 379-391 
    Details
    ISSN: 1432-1106
    Schlagwort(e): Auditory cortex ; Cross-correlograms ; Cross-interval histograms ; Burst-firing ; Neural interaction ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract In order to allow the relation of functional connectivity patterns (inferred from cross-correlograms) to structural connectivity (the anatomical substrate), we analyzed cross-correlogram peaks for spontaneous and stimulated activity in the auditory cortex. It was assumed that the broad correlograms, usually encountered, represent neural connectivity as well as secondary effects such as intrinsic firing patterns, global synchrony related to the ongoing electroencephalographic activity, and stimulus-related effects. Data were collected from 604 neuron pairs recorded under spontaneous conditions in primary auditory cortex of seven juvenile (30–70 days) and nine adult cats. Three hundred and six pairs (51%) had a peak cross-correlation coefficient significantly different from zero. For 113 neuron pairs out of this subgroup, correlations were calculated also for spike trains recorded during click stimulation. After a combined burst-correction and deconvolution procedure was carried out, the correlation peak strengths were not significantly changed for spontaneous activity, but peak width was narrower for single-electrode pairs than for dual-electrode pairs, suggesting a better synchronization for neighboring neurons. Under click stimulation conditions, overall peak synchronization strength was independent of interelectrode distance, whereas, after correction for secondary and stimulus effects, peak synchronization was significantly lower for dual-electrode pairs. However, the primary peak width for single-electrode pairs under stimulus conditions was no longer different from that of dual-electrode pairs. This implies that both under spontaneous and stimulus conditions secondary effects largely obscure any underlying correlation produced by anatomical connectivity. The secondary effects may be the result of intrinsic as well as network properties in auditory cortex and may functionally be more important than the weak primary effects resulting from anatomical connections. Cross-interval analysis suggests that the correlations in auditory cortex are dynamic and may show random switching between states of stronger and weaker synchronization.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00229138
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 26
    Digitale Medien
    Digitale Medien
    Intrinsic tone and distensibility of in vitro and in situ cat pulmonary arteries (1996)
    Springer
    Lung 174 (1996), S. 291-301 
    Details
    ISSN: 1432-1750
    Schlagwort(e): Pulmonary artery ; Vascular angiography ; Cat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract This study was designed to determine the in vitro and in situ diameter vs pressure relationship of 200- to 1,200-μm diameter pulmonary arteries in the cat. Diameter vs pressure relationships of these arteries were obtained using two methods, microscopic observation of in vitro cannulated and pressurized arteries and X-ray angiography of in situ arteries. Both in vitro and in situ arteries were studied first under normal conditions and then after reducing tone with Ca2+-free solution (in vitro) or papaverine (in situ). In vitro arteries commonly increased their tone in response to elevated transmural pressure, and in some cases, the diameter actually decreased as pressure increased. This behavior was not observed in the in situ arteries. The major difference between in vitro and in situ arteries was that when the in vitro arteries were relaxed, the slope of the diameter vs pressure curves increased, whereas the slope was not altered significantly by relaxation of the in situ arteries. This difference is emphasized by the increased distensibility with relaxation of the in vitro arteries but the decreased distensibility with relaxation of the in situ arteries. The results of this study suggest that, at least in the cat, small pulmonary arteries possess a mechanism that is dormant in the in situ environment within the normal lung. However, the potential for pressure-induced constriction may be unmasked by changing the vessel history and/or environment. Extrapolating results obtained from in vitro pulmonary arteries to the in situ situation should therefore be done with caution. Studies directed at what factors contribute to differences in the responses of in vitro and in situ arteries might help in understanding pulmonary vascular pathophysiology.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00176188
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 27
    Digitale Medien
    Digitale Medien
    Ion exchange purification of G6PDH from unclarified yeast cell homogenates using expanded bed adsorption (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 49 (1996), S. 204-216 
    Details
    ISSN: 0006-3592
    Schlagwort(e): expanded bed adsorption ; bakers' yeast ; G6PDH ; STREAMLINE ion exchange adsorbents ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The use of expanded beds of STREAMLINE ion exchange adsorbents for the direct extraction of an intracellular enzyme glucose-6-phosphate dehydrogenase (G6PDH) from unclarified yeast cell homogenates has been investigated. It has been demonstrated that such crude feedstocks can be applied to the bed without prior clarification steps. The purification of G6PDH from an unclarified yeast homogenate was chosen as a model system containing the typical features of a direct extraction technique. Optimal conditions for the purification were determined in small scale, packed bed experiments conducted with clarified homogenates. Results from these experiments were used to develop a preparative scale separation of G6PDH in a STREAMLINE 50 EBA apparatus. The use of an on-line rotameter for measuring and controlling the height of the expanded bed when operated in highly turbid feedstocks was demonstrated. STREAMLINE DEAE has been shown to be successful in achieving isolation of G6PDH from an unclarified homogenate with a purification factor of 12 and yield of 98% in a single step process. This ion exchange adsorbent is readily cleaned using simple cleaning-in-place procedures without affecting either adsorption or the bed expansion properties of the adsorbent after many cycles of operation. The ability of combining clarification, capture, and purification in a single step will greatly simplify downstream processing flowsheets and reduce the costs of protein purification. © 1996 John Wiley & Sons, Inc.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
  • 28
    Digitale Medien
    Digitale Medien
    Rat hepatocyte morphology and function on lactose-derivatized polystyrene surfaces (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 49 (1996), S. 259-265 
    Details
    ISSN: 0006-3592
    Schlagwort(e): hepatocytes ; lactose-derivatized polystyrene ; polystyrene ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Hepatocytes isolated from male Fisher 344VF rats were cultured on two substrates, collagen I and a lactose-derivatized polystyrene (PS-lactose), to compare morphological and functional differences. Hepatocyte morphology changed dramatically depending upon the substrate, shown through actin cytoskeletal staining and scanning electron microscopy. Functional assays performed included albumin secretion, reduced glutathione content, UDP-glucuronosyl transferase, and cytochrome P4501A1 activity. The presence of dexamethasone and dimethylsulfoxide (DMSO) in the media was required for the maintenance of several differentiated functions for cells cultured on collagen. In general, cells cultured on the PS-lactose substrate showed a much slower loss of function over the same period of time. The maintenance of differentiated function of cells on PS-lactose was enhanced with the addition of dexamethasone and DMSO. This is the first report of a culture system in which hepatocytes, cultured on a polymer substrate without additional protein coatings or media additives, have been able to maintain differentiated functions for up to 1 week. © 1996 John Wiley & Sons, Inc.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
  • 29
    Digitale Medien
    Digitale Medien
    Conservative chemical modification of proteins to study the effects of a single protein property on partitioning in aqueous two-phase systems (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 49 (1996), S. 290-299 
    Details
    ISSN: 0006-3592
    Schlagwort(e): proteins, modified ; partitioning in aqueous system ; thaumatin ; β-lactoglobulin ; BSA ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Relatively conservative modifications of three proteins were carried out to alter their surface properties. The protein properties modified were hydrophobicity and charge. This was done by acylation of amino groups with anhydrides. For the hydrophobic modification experiments, two proteins (β-lactoglobulin and bovine serum albumin [BSA]) and four anhydrides (hexanoic, butyric, succinic, acetic) were used. For the modification of surface charge the protein thaumatin was selected and various proportions of the free amino groups were blocked with acetic anhydride to give a series of proteins with differing isoelectric points. Detailed characterization and purification of selected modified proteins was carried out including molecular weight measurements and conformational analysis. The criteria used for selecting the modified proteins for subsequent investigation of their partitioning in aqueous two-phase systems (ATPS) is described. With a judicious choice of starting material it was found that limited chemical modifications to proteins could effectively alter surface hydrophobicity or charge almost independently, with little effect on other molecular properties. It appears, however, that the method for chemical modification and the reaction conditions must also be carefully controlled. © 1996 John Wiley & Sons, Inc.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
  • 30
    Digitale Medien
    Digitale Medien
    Use of chemically modified proteins to study the effect of a single protein property on partitioning in aqueous two-phase systems: Effect of surface charge (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 49 (1996), S. 309-315 
    Details
    ISSN: 0006-3592
    Schlagwort(e): surface charge ; proteins, modified ; partitioning in aqueous system ; thaumatin ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A series of charge-modified thaumatins with different values of surface charge were partitioned in aqueous two-phase systems (ATPS) to study the effect of surface charge as a single property on partitioning. Electrophoretic mobility of the proteins in titration curves was used as a measure of surface charge. Four modified proteins derived from thaumatin with the following values of isoelectric point: 8.70, 8.15, 5.60, and 4.50 were used for partitioning. The resolution of the systems in terms of protein surface charge was calculated. Partitioning of modified thaumatins in PEG 4000/dextran systems with phosphate buffer, Tris buffer, NaCl, KCl, and sulfate salts was carried out. Among the sulfate salts tested, the addition of 50 mM Li2SO4 to the system buffered with phosphate gave the highest value of resolution for differences in surface protein charge (RSPC). It shows a decrease in the value of K (partition coefficient) with an increase in the protein's charge. The addition of 100 mM KCl to the system promoted the opposite effect on the RSPC value. Charge-modified proteins were partitioned in PEG/salt systems to investigate the ability of these systems for resolving differences in surface charge. The PEG/citrate system seemed to have almost no ability for resolving proteins on the basis of surface charge differences; PEG/phosphate systems had some capability for resolving differently charged proteins. The more negative proteins tended to have higher values of K than the more positively charged fractions. The use of charge-modified proteins allowed the investigation of the effect of protein surface charge on partitioning in aqueous two-phase systems independently from other protein parameters as they were prepared from a common parent protein thaumatin. This technique provides an interesting novel tool to investigate the effect of protein surface charge on partitioning in ATPS taking protein charge as an independent parameter. © 1996 John Wiley & Sons, Inc.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
  • 31
    Digitale Medien
    Digitale Medien
    A versatile oxygenator and perfusion system for magnetic resonance studies (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 49 (1996), S. 348-354 
    Details
    ISSN: 0006-3592
    Schlagwort(e): oxygenator ; NMR spectroscopy ; organ perfusion ; mammalian cell culture ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A compact, reusable membrane oxygenator has been constructed for the perfusion of cultured cells and isolated organs. While the oxygenator was designed to be compatible with nuclear magnetic resonance (NMR) spectroscopy studies, it can also be used for any experiment which requires warming and oxygenation of perfusates. For the NMR studies, the oxygenator can be positioned at the opening of the magnet bore which allows oxygenation and warming of the perfusate immediately prior to delivery to the tissue, therefore eliminating problems with heat or oxygen loss which may occur with the long perfusion lines. © 1996 John Wiley & Sons, Inc.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bit.260490302
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 32
    Digitale Medien
    Digitale Medien
    Fluid shear stress induction of the transcriptional activator c-fos in human and bovine endothelial cells, HeLa, and Chinese hamster ovary cells (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 49 (1996), S. 383-390 
    Details
    ISSN: 0006-3592
    Schlagwort(e): c-fos protein ; endothelium ; hemodynamics ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The c-fos protein belongs to a family of transcriptional cofactors that can complex with proteins of the Jun family and activate mRNA transcription from gene promoters containing an activator protein 1 (AP-1) binding element. The shear stress inducibility of the c-fos protein was studied in human and animal cell lines of vastly different origins. Primary human umbilical vein endothelial cells (HUVEC), bovine aortic endothelial cells (BAEC, passage 2-14), HeLa cells, and Chinese hamster ovary (CHO) cells were subjected to steady laminar shear stress using a parallel plate flow apparatus. After 1 h of flow exposure at 25 dyn/cm2, the c-fos levels in nuclei of shear stress HUVEC, BAEC, HeLa, and CHO were 5.4 ± 2.0 (n = 3), 2.25 ± 1.38 (n = 6), 2.14 ± 0.07 (n = 8), 1.92 ± 0.58 (n = 2) times higher, respectively, than in matched stationary controls. Flow exposure at 4 dyn/cm2 caused no enhancement of c-fos levels in any of the cell lines tested, but caused significant reduction in c-fos expression in the HeLa cells. The c-fos induction by shear stress could be blocked by pharmacological agents. For example, the flow induction of the c-fos protein levels was blocked by 50% with the preincubation of HUVEC with a protein kinase C inhibitor, H7 (10 μM) and blocked completely in HeLa cells preincubated with the phospholipase C inhibitor, neomycin (5 mM). The minimum time of shear stress exposure required to induce the c-fos protein expression in HeLa cells was found to be as low as 1 min. By Northern analysis, the c-fos mRNA levels were found to be elevated in BAEC, CHO, and HeLa cells exposed to 25 dyn/cm2 for 30 min. These studies indicate that c-fos induction is a consistent genetic response in a variety of mammalian cells that may alter cellular phenotype in mechanical environments. © 1996 John Wiley & Sons, Inc.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
  • 33
    Digitale Medien
    Digitale Medien
    Vancomycin production in batch and continuous culture (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 49 (1996), S. 412-420 
    Details
    ISSN: 0006-3592
    Schlagwort(e): Amycolatopsis orientalis ; vancomycin production ; chemostat culture ; phosphate inhibition ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Production of the glycopeptide antibiotic vancomycin by two Amycolatopsis orientalis strains was examined in batch shake flask culture in a semidefined medium with peptone as the nitrogen source. Different growth and production profiles were observed with the two strains; specific production (Yp/x) was threefold higher with strain ATCC 19795 than with strain NCIMB 12945. A defined medium with amino acids as the nitrogen source was developed by use of the Plackett-Burman statistical screening method. This technique identified certain amino acids (glycine, phenylalanine, tyrosine, and arginine) that gave significant increased specific production, whereas phosphate was identified as inhibitory for high specific vancomycin production. Experiments made with the improved medium and strain ATCC 19795 showed that vancomycin production kinetics were either growth dissociated or growth associated, depending on the amino acid concentration. In chemostat culture at a constant dilution rate (0.087 h-1), specific vancomycin production rate (qvancomycin) decreased linearly as the medium phosphate concentration was increased from 2 to 8 mM. In both phosphate and glucose limited chemostats, qvancomycin was a function of specific growth rate; the maximum value was observed at D = 0.087 h-1 (52% of the maximum specific growth rate). Under phosphate limited growth conditions, qvancomycin was threefold higher (0.37 mg/g dry weight/h) than under glucose limitation (0.12 mg/g dry weight/h). © 1996 John Wiley & Sons, Inc.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
  • 34
    Digitale Medien
    Digitale Medien
    On-line monitoring of respiration in recombinant-baculovirus infected and uninfected insect cell bioreactor cultures (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 50 (1996), S. 36-48 
    Details
    ISSN: 0006-3592
    Schlagwort(e): insect cell culture ; Sf-9 cells ; respiration ; bioreactor ; on-line monitoring ; baculovirus expression vector system ; recombinant proteins ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Respiration rates in Spodoptera frugiperda (Sf-9) cell bioreactor cultures were successfully measured on-line using two methods: The O2 uptake rate (OUR) was determined using gas phase pO2 values imposed by a dissolved oxygen controller and the CO2 evolution rate (CER) was measured using an infrared detector. The measurement methods were accurate, reliable, and relatively inexpensive. The CER was routinely determined in bioreactor cultures used for the production of several recombinant proteins. Simple linear relationships between viable cell densities and both OUR and CER in exponentially growing cultures were used to predict viable cell density. Respiration measurements were also used to follow the progress of baculoviral infections in Sf-9 cultures. Infection led to increases in volumetric and per-cell respiration rates. The relationships between respiration and several other culture parameters, including viable cell density, cell protein, cell volume, glucose consumption, lactate production, viral titer, and recombinant β-galactosidase accumulation, were examined. The extent of the increase in CER following infection and the time postinfection at which maximum CER was attained were negatively correlated with the multiplicity of infection (MOI) at multiplicities below the level required to infect all the cells in a culture. Delays in the respiration peak related to the MOI employed were correlated with delays in the peak in recombinant protein accumulation. DO levels in the range 5-100% did not exert any major effects on viable cell densities, CER, or product titer in cultures infected with a baculovirus expressing recombinant β-galactosidase. © 1996 John Wiley & Sons, Inc.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
  • 35
    Digitale Medien
    Digitale Medien
    Masthead (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 50 (1996) 
    Details
    ISSN: 0006-3592
    Schlagwort(e): Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bit.260500101
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 36
    Digitale Medien
    Digitale Medien
    Aggregation of ligand-modified liposomes by specific interactions with proteins. II: Biotinylated liposomes and antibiotin antibody (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 50 (1996), S. 169-183 
    Details
    ISSN: 0006-3592
    Schlagwort(e): liposomes ; biotin ; aggregation kinetics ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The aggregation of biotinylated phospholipid vesicles (liposomes) cross-linked by antibiotin IgG was studied experimentally and theoretically. The liposomes were either low density liposomes that contained 0.4 mol% biotinylated phospholipid (≈100 exposed biotin molecules per liposome), or high density liposomes that contained 2.7 mol% biotinylated phospholipid (≈1000 exposed biotin molecules per liposome). The solution turbidity and mean particle size measured by quasi-elastic light scattering (QLS) were monitored throughout the aggregation. Three different lots of antibiotin antibodies, each with different association constants and binding heterogeneities, were used. The antibody binding characteristics affected the aggregation rates. The aggregation kinetics were analyzed using a model based on the Smoluchowski theory of aggregation, fractal concepts of aggregate microstructure, and Rayleigh and Mie light scattering theory. The experimental conditions of liposome concentration, protein concentration, and ligand density under which aggregation occurred correlated well with calculated sticking probabilities based on isotherms describing the adsorption of antibiotin antibody to the liposomes. These results are compared with prior observations made when avidin was used as the cross-linking protein. © 1996 John Wiley & Sons, Inc.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
  • 37
    Digitale Medien
    Digitale Medien
    Masthead (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 50 (1996) 
    Details
    ISSN: 0006-3592
    Schlagwort(e): Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bit.260500201
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 38
    Digitale Medien
    Digitale Medien
    Collagenase digestion of bone fragments in microgravity (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 50 (1996), S. 211-216 
    Details
    ISSN: 0006-3592
    Schlagwort(e): microgravity ; bioprocessing ; sedimentation ; turbulence ; collagenase ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The effect of a quiescent microgravity fluid environment on the activity of collagenase directed at demineralized bone fragments was investigated over a period of 10 days. Enzyme treatment resulted in greater mass loss in microgravity, with nearly three times the loss of mass during Space Shuttle mission STS-62 compared to the stationary ground control. Clinorotation enhanced the loss of mass relative to a stationary control, but this increase was still significantly less than the increase with exposure to microgravity. This suggests the detrimental influence of turbulence on the enzyme function and the benefit of using microgravity to provide both low turbulence and uniformity of unequally dense materials within the reaction chamber. The results are considered for their general applicability to a variety of bioprocessing applications that may be enhanced in microgravity. © 1996 John Wiley & Sons, Inc.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bit.260500203
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 39
    Digitale Medien
    Digitale Medien
    Mini-review: Mechanical factors affecting cartilage regeneration in vitro (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 50 (1996), S. 430-437 
    Details
    ISSN: 0006-3592
    Schlagwort(e): cartilage ; tissue regeneration ; chondrocytes ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: In the last 5 to 10 years, tissue engineering has revolutionized the way in which medical researchers and clinicians are thinking of and, in some cases, actually treating diseases involving tissue damage and destruction. One such disease, osteoarthritis, results from progressive degeneration of articular cartilage, which has a limited ability to repair itself. With tissue engineering, scientists are now able to regenerate cartilage in vitro from isolated mature chondrocytes. While the regeneration process is still not fully understood, enough has been learned that physicians are already implanting cultured chondrocytes into humans and other animals in the hopes of effecting joint repair. One aspect which has not been fully explored is the effect of mechanical stress on developing and implanted cartilage, especially over the long term. This article will review in brief what is now known about the mechanical factors affecting cartilage regeneration in vitro and what still remains to be determined for optimum tissue engineering of cartilage constructs. © 1996 John Wiley & Sons, Inc.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
  • 40
    Digitale Medien
    Digitale Medien
    Osteoblast migration on poly(α-hydroxy esters) (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 50 (1996), S. 443-451 
    Details
    ISSN: 0006-3592
    Schlagwort(e): osteoblast ; migration ; poly(αhydroxy esters) ; poly(DL-lactic-co-glycolic acid) ; PLGA ; biodegradable polymers ; tissue engineering ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: We investigated the migration of rat calvaria osteoblast populations on poly(α-hydroxy ester) films for up to 14 days to determine effects of substrate composition and culture conditions on the migratory characteristics of osteoblasts. Initial osteoblast culture conditions included cell colonies formed by seeding a high (84,000 cells/cm2) or low (42,000 cells/cm2) density of isolated osteoblasts on the polymer films, and bone tissue cultures formed by plating bone chips directly on the substrates. High density osteoblast colonies cultured and allowed to migrate and proliferate radially on 85:15 poly(DL-lactic-co-glycolic acid) (PLGA) films, 75:25 PLGA films, and tissue culture polystyrene controls demonstrated that the copolymer ratio in the polymer films did not affect the rate of increase in substrate surface area (or culture area) covered by the growing cell colony. However, the rate of increase in culture area was dependent on the initial osteoblast seeding density. Initial cell colonies formed with a lower osteoblast seeding density on 75:25 PLGA resulted in a lower rate of increase in culture area, specifically 4.9 ± 0.3 mm2/day, versus 14.1 ± 0.7 mm2/day for colonies seeded with a higher density of cells on the same polymer films. The proliferation rate for osteoblasts in the high and low density seeded osteoblast colonies did not differ, whereas the proliferation rate for the osteoblasts arising from the bone chips was lower than either of these isolated cell colonies. Confocal and light microscopy revealed that the osteoblast migration occurred as a monolayer of individual osteoblasts and not a calcified tissue front. These results demonstrated that cell seeding conditions strongly affect the rates of osteoblast migration and proliferation on biodegradable poly(α-hydroxy esters). © 1996 John Wiley & Sons, Inc.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
  • 41
    Digitale Medien
    Digitale Medien
    Different measures of human hematopoietic cell culture performance are optimized under vastly different conditions (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 50 (1996), S. 505-513 
    Details
    ISSN: 0006-3592
    Schlagwort(e): bone marrow ; hematopoiesis ; perfusion ; culture optimization ; stroma ; stem cells ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Hematopoiesis, the formation of mature blood cells from stem (LTC-IC) and progenitor (CFU-GM) cells in the bone marrow, is a complex tissue-forming process that leads to many important physiological functionalities. Consequently, a functioning ex vivo hematopoietic system has a variety of basic scientific and clinical uses. The design and operation of such a system presents the tissue engineer with challenges and choices. In this study, three culture variables were used to control ex vivo human hematopoiesis. Systematic variation of inoculum density (ID), medium exchange interval (MEI), and the use of preformed stroma (PFS) showed that (1) all three variables significantly influenced culture performance, (2) the three variables interacted strongly, and (3) the variables could be manipulated to achieve the optimization of different performance criteria. Donor-to-donor variability in culture performance was great at low ID but was minimized at higher ID. PFS had a large positive effect on cell and CFU-GM output at low ID, but had minimal effect at higher ID. In fact, PFS caused a decrease in LTC-IC output at high ID. The effects of PFS indicated that stromal cell elements became more limiting than proliferative cell elements as ID was reduced.In cultures without PFS, maximum cell output was obtained with high ID using a short MEI, whereas the greatest cell expansion ratio was obtained at low ID with an intermediate MEI. Maximum CFU-GM output was obtained from cultures with high ID using a short to intermediate MEI, whereas the greatest CFU-GM expansion ratio was obtained at intermediate ID with an intermediate MEI. The addition of PFS altered the locations of these maxima. In general, PFS moved the maxima to lower ID, and culture output became more sensitive to MEI. Therefore, the optimization of one performance criterion always resulted in a decline of the others. This study demonstrates that ex vivo tissue function is sensitive to many culture variables in an interactive fashion and that systematic multivariable studies are required to characterize tissue function. Once the effects of individual variables and their interactions are known, this knowledge can be used to optimize tissue performance with respect to desired criteria. © 1996 John Wiley & Sons, Inc.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
  • 42
    Digitale Medien
    Digitale Medien
    Masthead (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 50 (1996) 
    Details
    ISSN: 0006-3592
    Schlagwort(e): Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bit.260500501
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 43
    Digitale Medien
    Digitale Medien
    Thermal stability studies of a globular protein in aqueous poly(ethylene glycol) by 1H NMR (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 51 (1996), S. 410-421 
    Details
    ISSN: 0006-3592
    Schlagwort(e): lysozyme ; thermal stability ; 1H NMR ; conformational flexibility ; melting temperature ; PEG ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The reversible folding destabilization of hen lysozyme has been confirmed by a melting temperature (Tm) decrease in aqueous poly(ethylene glycol) (PEG). The percent denatured, extracted from the histidine 15 C2H (H15 C2H) native and denatured peak areas from 500-MHz one-dimensional proton nuclear magnetic resonance (1D 1H NMR) spectra in D2O, was analyzed through denaturation temperatures at 0% and 20% (w/w) PEG 1000. The lysozyme (3.5 mM) Tm decreased by 4.2°C and 7.1°C in 20% (w/w) PEG 1000 at pH 3.8 and 3.0, respectively. The Tm decreased with increasing lysozyme concentration. Additionally, the temperature-induced resonance migrations of 17 protons from 8 residues indicate that the native lysozyme structure undergoes temperature-induced conformational changes. The changes were essentially identical in both 0% and 20% (w/w) PEG 1000 at both pH 3.0 and 3.8. This small, local restructuring of the hydrophobic box region may be a manifestation of temperature-dependent solution hydrophobicity, whereas active-site cleft fluctuations may be due to the inherent active-site flexibility. The lysozyme structure in PEG at 35°C was determined to be essentially native from the 1H nuclear Overhauser effect spectroscopy (NOESY) fingerprint regions. Additionally, lysozyme chemical shifts, from 1D spectra, in PEG 200, 300, and 1000 at 35°C and various concentrations were essentially identical, further confirming that the conformation remains native in various PEG solutions. © 1996 John Wiley & Sons, Inc.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
  • 44
    Digitale Medien
    Digitale Medien
    Factors affecting cellulose hydrolysis and the potential of enzyme recycle to enhance the efficiency of an integrated wood to ethanol process (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 51 (1996), S. 375-383 
    Details
    ISSN: 0006-3592
    Schlagwort(e): cellulase ; enzyme recycling ; enzyme adsorption ; lignocellulosic hydrolysis ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Past technoeconomic modeling work has identified the relatively large contribution that enzymatic hydrolysis adds to the total cost of producing ethanol from lignocellulosic substrates. This cost was primarily due to the high concentration of enzyme and long incubation time that was required to obtain complete hydrolysis. Although enzyme and substrate concentration and end-product inhibition influenced the rate of hydrolysis, the effect was less pronounced during the initial stages of hydrolysis. During this time most of the cellulases were adsorbed onto the unhydrolyzed residue. By recycling the cellulases adsorbed to the residual substrate remaining after an initial 24 h, a high rate of hydrolysis, with low overall residence time and minimal cellulase input, could be achieved for several rounds of enzyme recycle. A comparison of the front end (pretreatment, fractionation, and hydrolysis) of a softwood/hardwood to ethanol process indicated that the lignin associated with the softwood-derived cellulose stream limited the number of times the cellulose containing residue could be recycled. © 1996 John Wiley & Sons, Inc.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
  • 45
    Digitale Medien
    Digitale Medien
    Sparging and agitation-induced injury of cultured animals cells: Do cell-to-bubble interactions in the bulk liquid injure cells? (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 51 (1996), S. 399-409 
    Details
    ISSN: 0006-3592
    Schlagwort(e): cell damage ; cell culture ; bubble aeration ; agitation ; bubble coalescence and breakup ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: It has been established that the forces resulting from bubbles rupturing at the free air (gas)/liquid surface injure animal cells in agitated and/or sparged bioreactors. Although it has been suggested that bubble coalescence and breakup within agitated and sparged bioreactors (i.e., away from the free liquid surface) can be a source of cell injury as well, the evidence has been indirect. We have carried out experiments to examine this issue. The free air/liquid surface in a sparged and agitated bioractor was eliminated by completely filling the 2-L reactor and allowing sparged bubbles to escape through an outlet tube. Two identical bioreactors were run in parallel to make comparisons between cultures that were oxygenated via direct air sparging and the control culture in which silicone tubing was used for bubble-free oxygenation. Thus, cell damage from cell-to-bubble interactions due to processes (bubble coalescence and breakup) occurring in the bulk liquid could be isolated by eliminating damage due to bubbles rupturing at the free air/liquid surface of the bioreactor. We found that Chinese hamster ovary (CHO) cells grown in medium that does not contain shear-protecting additives can be agitated at rates up to 600 rpm without being damaged extensively by cell-to bubble interactions in the bulk of the bioreactor. We verified this using both batch and high-density perfusion cultures. We tested two impeller designs (pitched blade and Rushton) and found them not to affect cell damage under similar operational conditions. Sparger location (above vs. below the impeller) had no effect on cell damage at higher agitation rates but may affect the injury process at lower agitation intensities (here, below 250 rpm). In the absence of a headspace, we found less cell damage at higher agitation intensities (400 and 600 rpm), and we suggest that this nonintuitive finding derives from the important effect of bubble size and foam stability on the cell damage process. © 1996 John Wiley & Sons, Inc.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
  • 46
    Digitale Medien
    Digitale Medien
    Modulation of the phosphate-starvation response in Escherichia coli by genetic manipulation of the polyphosphate pathways (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 51 (1996), S. 434-438 
    Details
    ISSN: 0006-3592
    Schlagwort(e): polyphosphate ; Escherichia coli ; phosphate starvation ; gene expression ; heterologous ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The effect of intracellular polyphosphate on the phosphate-starvation response in Escherichia coli was studied by genetically manipulating the intracellular polyphosphate levels and by performing phosphate shifts on the genetically engineered strains. Strains that produced large quantities of polyphosphate and were able to degrade it induced the phosphate-starvation response to a lesser extent than wild-type strains, whereas strains that were unable to degrade a large intracellular polyphosphate pool induced the phosphate-starvation response to a greater extent than wild-type strains. These results have important implications for expression of heterologous genes under control of the phoA promoter. © 1996 John Wiley & Sons, Inc.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
  • 47
    Digitale Medien
    Digitale Medien
    Effect of high shear on proteins (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 51 (1996), S. 458-465 
    Details
    ISSN: 0006-3592
    Schlagwort(e): concentric-cylinder shear device ; rotor/stator homogenization ; shear ; shear rate ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Shear is present in almost all bioprocesses and high shear is associated with processes involving agitation and emulsification. The purpose of this study is to investigate the effect of high shear and high shear rate on proteins. Two concentric cylinder-based shear systems were used. One was a closed concentric-cylinder shear device (CCSD) and the other was a homogenizer with a rotor/stator assembly. Mathematical modeling of these systems allowed calculation of the shear rate and shear. The CCSD generated low shear rates (a few hundred s-1), whereas the homogenizer could generate very high shear rates (〉 105 s-1). High shear could be achieved in both systems by increasing the processing time. Recombinant human growth hormone (rhGH) and recombinant human deoxyribonuclease (rhDNase) were used as the model proteins in this study. It was found that neither high shear nor high shear rate had a significant effect on protein aggregation. However, a lower melting temperature and enthalpy were detected for highly sheared rhGH by using scanning microcalorimetry, presumably due to some changes in protein's conformation. Also, SDS-PAGE indicated the presence of low molecular-weight fragments, suggesting that peptide bond breakage occurred due to high shear. rhDNase was relatively more stable than rhGH under high shear. No conformational changes and protein fragments were observed. © 1996 John Wiley & Sons, Inc.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
  • 48
    Digitale Medien
    Digitale Medien
    Properties of two insect cell lines useful for the baculovirus expression system in serum-free culture (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 51 (1996), S. 494-499 
    Details
    ISSN: 0006-3592
    Schlagwort(e): cell metabolism ; baculovirus ; insect cells ; recombinant protein OSF-2 ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The properties of Sf9 and Tn5 insect cells were analyzed comparatively under serum-free culture conditions. Sf9 cells in SF900II medium apparently utilized sucrose as a primary nutrient both before and after virus infection, yielding small amounts of lactate and ammonia. Tn5 cells in Excell 401 medium consumed all the nutrients examined, including sucrose. The productivity of a recombinant glycoprotein, OSF-2, by Tn5 cells, was moderate in both monolayer and spinner cultures, but the ability to secrete it was compromised in the former case. Relative to the Tn5 cultures, Sf9 produced 30-fold more OSF-2 in either culture mode. © 1996 John Wiley & Sons, Inc.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
  • 49
    Digitale Medien
    Digitale Medien
    NMR imaging of heavy metal absorption in alginate, immobilized cells, and kombu algal biosorbents (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 51 (1996), S. 538-543 
    Details
    ISSN: 0006-3592
    Schlagwort(e): NMR imaging ; biosorption ; alginate ; shrinking core model ; Laminaria ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: In this contribution, an NMR imaging study of heavy metal absorption in alginate, immobilized-cell biosorbents, and kombu (Laminaria japonica) algal biomass is presented. This method provides the good possibility of directly monitoring the time evolution of the spatial distribution of the ions in the materials. From these results, we demonstrate that rare earth ions are absorbed with a steep reaction front that can be described very well with a modified shrinking core model, while copper ions are absorbed with a more diffuse front.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
  • 50
    Digitale Medien
    Digitale Medien
    Enzymatic resolution of 1-phenyl-1,2-ethanediol by enantioselective oxidation: Overcoming product inhibition by continuous extraction (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 51 (1996), S. 544-550 
    Details
    ISSN: 0006-3592
    Schlagwort(e): oxidoreductase ; chiral alcohol ; racemic resolution ; membrane reactor ; continuous extraction ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Oxidations of alcohols by alcohol dehydrogenases often suffer from low conversions and slow reaction rates due to severe product inhibition. This can be overcome by continuous product extraction, because only the concentrations, but not the kinetic parameters, can be changed. As a consequence, it is favorable to apply a differential circulation reactor with continuous product extraction, where only a small amount of product is formed per cycle. The product is then directly extracted using a microporous hydrophobic hollow fiber membrane. This results in an increase of the relative activity of the dehydrogenase at a given conversion. The reaction investigated is the kinetic resolution of racemic 1-phenyl-1,2-ethanediol by glycerol dehydrogenase (GDH). The resulting oxidation product, 2-hydroxyacetophenone, causes a strong product inhibition. Additionally, it reacts in a chemical reaction with the cofactor lowering its active concentration. Because the GDH needs β-nicotinamide adenine dinucleotide (NAD+) as a cofactor, lactate dehydrogenase is used to regenerate NAD+ from NADH by reducing pyruvate to (L)-lactate. A conversion of 50% with respect to the racemate and an enantiomeric excess 〉99% of the (S)-enantiomer was reached.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
  • 51
    Digitale Medien
    Digitale Medien
    Immobilization of DNA onto a polymer support and its potentiality as immunoadsorbent (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 51 (1996), S. 581-590 
    Details
    ISSN: 0006-3592
    Schlagwort(e): microfiber ; graft polymerization ; DNA immobilization ; immunoadsorbent ; DNA ; anti-DNA antibody ; systemic lupus erythematosus ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Immobilization of DNA to the surface of poly(ethylene terephthalate) (PET) microfibers with a high specific surface area of 0.83 m2/g was carried out to give the fiber surface an affinity for anti-DNA antibody. Following ozone oxidation, the microfibers were subjected to graft polymerization of monomers including acrylic acid, methacryloyloxyethyl phosphate, N,N-dimethylaminoethyl methacrylate, N-vinylformamide, and glycidyl methacrylate. Calf thymus DNA was immobilized to the grafted fiber surface through either covalent binding or polyion complexation with the grafted polymer chains. The highest surface density of DNA immobilized (0.6 μg/cm2) was obtained when DNA was immobilized through formation of phosphodiester linkage between the hydroxyl group of DNA and the phosphate group in grafted poly(methacryloyloxyethyl phosphate) using 1,1-carbonyldiimidazole, or through polyion complexation between the anionic DNA and the cationic grafted poly(N,N-dimethylaminoethyl methacrylate) chains. Batch adsorption of anti-DNA antibody to the grafted PET fibers with and without DNA immobilized on their surface was conducted with serum obtained from systemic lupus erythematosus model mice. The DNA-immobilized PET fibers exhibited a higher adsorption capacity and specificity than the others. In addition, the DNA-immobilized fibers effectively adsorbed human anti-DNA antibody.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
  • 52
    Digitale Medien
    Digitale Medien
    Comparing folding codes for proteins and polymers (1996)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 24 (1996), S. 335-344 
    Details
    ISSN: 0887-3585
    Schlagwort(e): protein design ; synthetic heteropolymer design ; energy matrix ; sequence degeneracy ; structural encodability ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: Proteins fold to unique compact native structures. Perhaps other polymers could be designed to fold in similar ways. The chemical nature of the monomer “alphabet” determines the “energy matrix” of monomer interactions - which defines the folding code, the relationship between sequence and structure. We study two properties of energy matrices using two-dimensional lattice models: uniqueness, the number of sequences that fold to only one structure, and encodability, the number of folds that are unique lowest-energy structures of certain monomer sequences. For the simplest model folding code, involving binary sequences of H (hydrophobic) and P (polar) monomers, only a small fraction of sequences fold uniquely, and not all structures can be encoded. Adding strong repulsive interactions results in a folding code with more sequences folding uniquely and more designable folds. Some theories suggest that the quality of a folding code depends only on the number of letters in the monomer alphabet, but we find that the energy matrix itself can be at least as important as the size of the alphabet. Certain multi-letter codes, including some with 20 letters, may be less physical or protein-like than codes with smaller numbers of letters because they neglect correlations among inter-residue interactions, treat only maximally compact conformations, or add arbitrary energies to the energy matrix.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
  • 53
    Digitale Medien
    Digitale Medien
    A simple model of chaperonin-mediated protein folding (1996)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 24 (1996), S. 345-351 
    Details
    ISSN: 0887-3585
    Schlagwort(e): energy landscape ; kinetic traps ; hydrophobic interaction ; multiple folding pathways ; chaperone action ; lattice models ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: Chaperonins are oligomeric proteins that help other proteins fold. They act, according to the “Anfinsen cage” or “box of infinite dilution” model, to provide private space, protected from aggregation, where a protein can fold. Recent evidence indicates, however, that proteins are often ejected from the GroEL chaperonin in nonnative conformations, and repeated cycles of binding and ejection are needed for successful folding. Some experimental evidence suggests that GroEL chaperonins can act as folding “catalysts” in an ATP-dependent manner even when no aggregation takes place. This implies that chaperonins must somehow recognize the kinetically trapped intermediate states of a protein. A central puzzle is how a chaperonin can catalyze the folding reaction of a broad spectrum of different proteins. We propose a physical mechanism by which chaperonins can flatten the energy barriers to folding in a nonspecific way. Using a lattice model, we illustrate how a chaperonin could provide a sticky surface that helps pull apart an incorrectly folded protein so it can try again to fold. Depending on the relative sizes of the protein and the chaperonin cavity, folding can proceed both inside and outside the chaperonin. Consistent with experiments, we find that the folding rate and amount of native protein can be considerably enhanced, or sometimes reduced, depending on the amino acid sequence, the chaperonin size, and the binding and ejection rates from the chaperonin.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
  • 54
    Digitale Medien
    Digitale Medien
    Solution structure of P01, a natural scorpion peptide structurally analogous to scorpion toxins specific for apamin-sensitive potassium channel (1996)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 24 (1996), S. 359-369 
    Details
    ISSN: 0887-3585
    Schlagwort(e): scorpion venom ; neurotoxin ; NMR ; structure-activity relationships ; calcium activated-potassium channel ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: The venom of the North African scorpion Androctonus mauretanicus mauretanicus possesses numerous highly active neurotoxins that specifically bind to various ion channels. One of these, P05, has been found to bind specifically to calcium-activated potassium channels and also to compete with apamin, a toxin extracted from bee venom. Besides the highly potent ones, several of these peptides (including that of P01) have been purified and been found to possess only a very weak, although significant, activity in competition with apamin. The amino acid sequence of P01 shows that it is shorter than P05 by two residues. This deletion occurs within an α-helix stretch (residues 5-12). This α-helix has been shown to be involved in the interaction of P05 with its receptor via two arginine residues. These two arginines are absent in the P01 sequence. Furthermore, a proline residue in position 7 of the P01 sequence may act as an α-helix breaker. We have determined the solution structure of P01 by conventional two-dimensional 1H nuclear magnetic resonance and show that 1) the proline residue does not disturb the α-helix running from residues 5 to 12; 2) the two arginines are topologically replaced by two acidic residues, which explains the drop in activity; 3) the residual binding activity may be due to the histidine residue in position 9; and 4) the overall secondary structure is conserved, i.e., an α-helix running from residues 5 to 12, two antiparallel stretches of β-sheet (residues 15-20 and 23-27) connected by a type I′ β-turn, and three disulfide bridges connecting the α-helix to the β-sheet.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
  • 55
    Digitale Medien
    Digitale Medien
    Thermally induced hydrogen exchange processes in small proteins as seen by FTIR spectroscopy (1996)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 24 (1996), S. 379-387 
    Details
    ISSN: 0887-3585
    Schlagwort(e): infrared spectroscopy ; protein structure ; unfolding ; RNase T1 ; RNase A ; histone-like protein HBsu ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: Fourier-transform infrared (FTIR) spectroscopy has been used to study the thermally induced exchange characteristics of those backbone amide protons which persist H-D exchange at ambient conditions in ribonuclease A, in wild type ribonuclease T1 and some of its variants, and in the histone-like protein HBsu. The H-D exchange processes were induced by increasing the thermal energy of the protein solutions in two ways: (i) by linearly increasing the temperature, and (ii) by a temperature jump. To trace the H-D exchange in the proteins, various infrared absorption bands known to be sensitive to H-D exchange were used as specific monitors. Characteristic H-D exchange curves were obtained from which the endpoints (TH/D) of H-D exchange could be determined. The H-D exchange curves, the TH/D-values and the phase transition temperatures Tm were used to estimate the structural flexibility and stability of the given proteins. It is suggested that time-resolved FTIR spectroscopy can be used to determine global stability parameters of proteins.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
  • 56
    Digitale Medien
    Digitale Medien
    A partial model of the erythropoietin receptor complex (1996)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 24 (1996), S. 394-401 
    Details
    ISSN: 0887-3585
    Schlagwort(e): cytokines ; homology modeling ; erythropoietin ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: A model of the structure of erythropoietin (Epo) is presented based on structural homology to other hemopoietic cytokines. A model of the erythropoietin receptor complex was made based on evidence that this includes a homodimer of the receptor chain with known sequence. Key interactions are noted which explain data from mutation experiments, although at not all residues believed to be important to binding of Epo are at the interface. This is consistent with the hypothesis that the Epo receptor complex includes proteins in addition to the cloned receptor chain that have been cross-linked to Epo (Todokoro et al., Proc. Natl. Acad. Sci. USA 84:4126-4130, 1987; Mayeux et al., J. Biol. Chem. 266:23380-23385, 1991) but not isolated.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
  • 57
    Digitale Medien
    Digitale Medien
    Crystallization and preliminary X-ray analysis of the Escherichia coli replication terminator protein complexed with DNA (1996)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 24 (1996), S. 402-403 
    Details
    ISSN: 0887-3585
    Schlagwort(e): Tus ; terminus site ; protein-DNA interaction ; replication arrest ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: Crystals of the Escherichia coli replication terminator protein (Tus) complexed with its binding site DNA were obtained by a microdialysis method using PEG 4000. They belong to the tetragonal space group P41212 or P43212 with the unit cell parameter: a = 68.1 Å, c = 230.7 Å and contain one protein-DNA complex in an asymmetric unit. The native data set has been collected to 2.7 Å resolution.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
  • 58
    Digitale Medien
    Digitale Medien
    Purification, crystallization, and preliminary crystallographic analysis of 3-deoxy-D-arabino-heptulosonate-7-phosphate synthase from Escherichia coli (1996)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 24 (1996), S. 404-406 
    Details
    ISSN: 0887-3585
    Schlagwort(e): DAHP synthase ; metalloenzyme ; shikimate pathway ; KDOP synthase ; affinity chromatography ; protein crystallography ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: The phenylalanine-regulated isozyme of 3-deoxy-D-arabino-heptulosonate-7-phosphate- synthase (DAHPS) from Escherichia coli, its binary complexes with either substrate, phosphoenolpyruvate (PEP), or feedback inhibitor, Phe, and its ternary complexes with either PEP or Phe plus metal cofactor (either Mn2+, Cd2+, or Pb2+) were crystallized from polyethylglycol (PEG) solutions. All crystals of the DAHPS without Phe belong to space group C2, with cell parameters a = 213.5 Å, b = 54.3 Å, c = 149.0 Å, β = 116.6°. All crystals of the enzyme with Phe also belong to space group C2, but with cell parameters a = 297.1 Å, b = 91.4 Å, c = 256.5 Å, and β = 148.2°.
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
  • 59
    Digitale Medien
    Digitale Medien
    Masthead (1996)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 24 (1996) 
    Details
    ISSN: 0887-3585
    Schlagwort(e): Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/prot.340240301
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 60
    Digitale Medien
    Digitale Medien
    Federal support for protein engineering (1996)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 24 (1996), S. 1-1 
    Details
    ISSN: 0887-3585
    Schlagwort(e): Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/prot.340240302
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 61
    Digitale Medien
    Digitale Medien
    Current protocols in protein science, edited by J.E. Coligan, B.M. Dunn, H.L. Ploegh, D.W. Speicher, and P.T. Wingfield. New York: Wiley, 1995, 864 pages (core) + 576 pages (4 supplements)/year (updated looseleaf), print and CD-ROM (1996)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 24 (1996), S. 409-409 
    Details
    ISSN: 0887-3585
    Schlagwort(e): Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/prot.340240303
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 62
    Digitale Medien
    Digitale Medien
    Errata (1996)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 24 (1996), S. 410-410 
    Details
    ISSN: 0887-3585
    Schlagwort(e): Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/prot.340240304
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 63
    Digitale Medien
    Digitale Medien
    The role of helix formation in the folding of a fully α-helical coiled coil (1996)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 24 (1996), S. 427-432 
    Details
    ISSN: 0887-3585
    Schlagwort(e): GCN4 ; protein folding ; folding kinetics ; helix formation ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: To determine when secondary structure forms as two chains coalesce to form an α-helical dimer, the folding rates of variants of the coiled coil region of GCN4 were compared. Residues at non-perturbing positions along the exterior length of the helices were substituted one at a time with alanine and glycine to vary helix propensity and therefore dimer stability. For all variants, the bimolecular folding rate remains largely unchanged; the unfolding rate changes to largely account for the change in stability. Thus, contrary to most folding models, widespread helix is not yet formed at the rate-limiting step in the folding pathway. The high-energy transition state is a collapsed form that contains little if any secondary structure, as suggested for the globular protein cytochrome c (Sosnick et al., Proteins 24:413-426, 1996).
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
  • 64
    Digitale Medien
    Digitale Medien
    Hydrophilicity of cavities in proteins (1996)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 24 (1996), S. 433-438 
    Details
    ISSN: 0887-3585
    Schlagwort(e): structure refinement ; buried water ; free energy calculation ; molecular dynamics simulation ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: Water molecules inside cavities in proteins constitute integral parts of the structure. We have sought a quantitative measure of the hydrophilicity of the cavities by calculating energies and free energies of introducing a water molecule into these cavities. A threshold value of the water-protein interaction energy at -12 kcal/mol was found to be able to distinguish hydrated from empty cavities. It follows that buried waters have entropy comparable to that of liquid water or ice. A simple consistent picture of the energetics of the buried waters provided by this study enabled us to address the reliability of buried waters assigned in experiments.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
  • 65
    Digitale Medien
    Digitale Medien
    Molecular collapse: The rate-limiting step in two-state cytochrome c folding (1996)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 24 (1996), S. 413-426 
    Details
    ISSN: 0887-3585
    Schlagwort(e): protein folding ; folding kinetics ; folding barriers ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: Experiments with cytochrome c (cyt c) show that an initial folding event, molecular collapse, is not an energetically downhill continuum as commonly presumed but represents a large-scale, time-consuming, cooperative barrier-crossing process. In the absence of later misfold-reorganization barriers, the early collapse barrier limits cyt c folding to a time scale of milliseconds. The collapse process itself appears to be limited by an uphill search for some coarsely determined transition state structure that can nucleate subsequent energetically downhill folding events. An earlier “burst phase” event at strongly native conditions appears to be a non-specific response of the unfolded chain to reduced denaturant concentration. The molecular collapse process may or may not require the co-formation of the amino- and carboxyl-terminal helices, which are present in an initial metastable intermediate directly following the rate-limiting collapse. After the collapse-nucleation event, folding can proceed rapidly in an apparent two-state manner, probably by way of a predetermined sequence of metastable intermediates that leads to the native protein structure (Bai et al., Science 269:192-197, 1995).
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
  • 66
    Digitale Medien
    Digitale Medien
    Patterns in ionizable side chain interactions in protein structures (1996)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 24 (1996), S. 439-449 
    Details
    ISSN: 0887-3585
    Schlagwort(e): salt bridges ; hydrogen bonds ; secondary structure ; ionizable side chains ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: In a selected set of 44 high-resolution, non-homologous protein structures, the intramolecular hydrogen bonds or salt bridges formed by ionizable amino acid side chains were identified and analyzed. The analysis was based on the investigation of several properties of the involved residues such as their solvent exposure, their belonging to a certain secondary structural element, and their position relative to the N- and C-termini of their respective structural element. It was observed that two-thirds of the interactions made by basic or acidic side chains are hydrogen bonds to polar uncharged groups. In particular, the majority (78%) of the hydrogen bonds between ionizable side chains and main chain polar groups (sch:mch bonds) involved at least one buried atom, and in 42% of the cases both interacting atoms were buried. In α-helices, the sch:mch bonds observed in the proximity of the C- and N-termini show a clear preference for acidic and basic side chains, respectively. This appears to be due to the partial charges of peptide group atoms at the termini of α-helices, which establish energetically favorable electrostatic interactions with side chain carrying opposite charge, at distances even greater than 4.5 Å. The sch:mch interactions involving ionizable side chains that belong either to β-strands or to the central part of α-helices are based almost exclusively on basic residues. This results from the presence of main chain carbonyl oxygen atoms in the protein core which have unsatisfied hydrogen bonding capabilities.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
  • 67
    Digitale Medien
    Digitale Medien
    Phylogenetic occurrence of coiled coil proteins: Implications for tissue structure in metazoa via a coiled coil tissue matrix (1996)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 24 (1996), S. 467-484 
    Details
    ISSN: 0887-3585
    Schlagwort(e): heptad repeat ; alpha helix ; intermediate filament ; nuclear matrix ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: We examined GenBank sequence files with a heptad repeat analysis program to assess the phylogenetic occurrence of coiled coil proteins, how heptad repeat domains are organized within them, and what structural/functional categories they comprise. Of 102,007 proteins analyzed, 5.95% (6,074) contained coiled coil domains; 1.26% (1,289) contained “extended” (〉 75 amino acid) domains. While the frequency of proteins containing coiled coils was surprisingly constant among all biota, extended coiled coil proteins were fourfold more frequent in the animal kingdom and may reflect early events in the divergence of plants and animals. Structure/function categories of extended coils also revealed phylogenetic differences. In pathogens and parasites, many extended coiled coil proteins are external and bind host proteins. In animals, the majority of extended coiled coil proteins were identified as constituents of two protein categories: 1) myosins and motors; or 2) components of the nuclear matrix-intermediate filament scaffold. This scaffold, produced by sequential extraction of epithelial monolayers in situ, contains only 1-2% of the cell mass while accurately retaining morphological features of living epithelium and is greatly enriched in proteins with extensive, interrupted coiled coil forming domains. The increased occurrence of this type of protein in Metazoa compared with plants or protists leads us to hypothesize a tissue-wide matrix of coiled coil interactions underlying metazoan differentiated cell and tissue structure.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
  • 68
    Digitale Medien
    Digitale Medien
    Ion pair formation of phosphorylated amino acids and lysine and arginine side chains: A theoretical study (1996)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 24 (1996), S. 495-501 
    Details
    ISSN: 0887-3585
    Schlagwort(e): ab initio calculations ; density functional theory ; semiempirical calculations ; solvent reaction field ; phosphoserine ; phosphothreonine ; phosphotyrosine ; hydrogen bonding ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: Protein phosphorylation is one of the major signal transduction mechanisms for controlling and regulating intracellular processes. Phosphorylation of specific hydroxylated amino acid side chains (Ser, Thr, Tyr) by protein kinases can activate numerous enzymes; this effect can be reversed by the action of protein phosphatases. Here we report ab initio (HF/6-31G* and Becke3LYP/6-31G*) and semiempirical (PM3) molecular orbital calculations pertinent to the ion pair formation of the phosphorylated amino acids with the basic side chains of Lys and Arg. Methyl-, ethyl-, and phenylphosphate, as well as methylamine and methylguanidinium were used as model compounds for the phosphorylated and basic amino acids, respectively. Phosphorylated amino acids were calculated as mono- and divalent anions. Our results indicate that the PSer/PThr ion pair interaction energies are stronger than those with PTyr. Moreover, the interaction energies with the amino group of Lys are generally more favorable than with the guanidinium group of Arg. The Lys amino groups form stable bifurcated hydrogen bonded structures; while the Arg guanidinium group can form a bidentate hydrogen bonded structure. Reasonable values for the interaction free energies in aqueous solution were obtained for some complexes by the inclusion of a solvent reaction field in the computation (PM3-SM3).
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
  • 69
    Digitale Medien
    Digitale Medien
    Towards meeting the paracelsus challenge: The design, synthesis, and characterization of paracelsin-43, an α-helical protein with over 50% sequence identity to an all-β protein (1996)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 24 (1996), S. 502-513 
    Details
    ISSN: 0887-3585
    Schlagwort(e): de novo design ; protein structure ; inverse folding ; genetic algorithms ; 1H NMR ; CD ; peptide ; protein folding ; methanol ; ethylene glycol ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: In response to the Paracelsus Challenge (Rose and Creamer, Proteins, 19:1-3, 1994), we present here the design, synthesis, and characterization of a helical protein, whose sequence is 50% identical to that of an all-β protein. The new sequence was derived by applying an inverse protein folding approach, in which the sequence was optimized to “fit” the new helical structure, but constrained to retain 50% of the original amino acid residues. The program utilizes a genetic algorithm to optimize the sequence, together with empirical potentials of mean force to evaluate the sequence-structure compatibility. Although the designed sequence has little ordered (secondary) structure in water, circular dichroism and nuclear magnetic resonance data show clear evidence for significant helical content in water/ethylene glycol and in water/methanol mixtures at low temperatures, as well as melting behavior indicative of cooperative folding. We believe that this represents a significant step toward meeting the Paracelsus Challenge.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
  • 70
    Digitale Medien
    Digitale Medien
    Crystallization and preliminary X-ray crystallographic studies of L-2-haloacid dehalogenase from Pseudomonas sp. YL (1996)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 24 (1996), S. 520-522 
    Details
    ISSN: 0887-3585
    Schlagwort(e): dehalogenase ; hydrolase ; Pseudomonas ; crystallization ; X-ray diffraction ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: The dimeric L-2-haloacid dehalogenase from Pseudomonas sp. YL, (subunit mass, 26179 Da), has been crystallized by vapor diffusion, supplemented by repetitive seeding, against a 50 mM potassium dihydrogenphosphate solution (pH 4.5) containing 15% (w/v) polyethylene glycol 8,000 and 1% (v/v) n-propanol. The crystals belong to the monoclinic space group C2 with unit cell dimensions of a = 92.21 Å, b = 62.78 Angst; c = 50.84 Å, and β = 122.4°, and contain two dehalogenase dimers in the unit cell. They are of good quality and diffract up to 1.5 Å resolution.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
  • 71
    Digitale Medien
    Digitale Medien
    Masthead (1996)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 24 (1996) 
    Details
    ISSN: 0887-3585
    Schlagwort(e): Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/prot.340240401
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 72
    Digitale Medien
    Digitale Medien
    Crystallization and preliminary X-ray diffraction study of 1,3,8-trihydroxynaphthalene reductase from Magnaporthe grisea (1996)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 24 (1996), S. 525-527 
    Details
    ISSN: 0887-3585
    Schlagwort(e): naphtol reductase ; melanin synthesis ; rice blast disease ; fungicide ; rational drug design ; crystallography ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: 1,3,8-Trihydroxynaphthalene reductase was crystallized in the presence of NADPH and the inhibitor tricyclazole. The crystals are trigonal, space group P3121 or its enantiomorph P3221. Two crystal forms with slightly different cell dimensions were obtained. Form A has unit cell dimensions a = b = 142.6 Å, c = 70.1 Å and form B cell dimensions a = b = 142.6 Å, c = 72.9 Å. The diffraction pattern of the latter crystal form extends to 2.5 Å resolution.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
  • 73
    Digitale Medien
    Digitale Medien
    Prediction of the secondary structure of HIV-1 gp120 (1996)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 25 (1996), S. 1-11 
    Details
    ISSN: 0887-3585
    Schlagwort(e): HIV-1 gp120 ; secondary structure ; prediction ; multiple alignment ; CD4-binding site ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: The secondary structure of HIV-1 gp120 was predicted using multiple alignment and a combination of two independent methods based on neural network and nearest-neighbor algorithms. The methods agreed on the secondary structure for 80% of the residues in BH10 gp120. Six helices were predicted in HIV strain BH10 gp120, as well as in 27 other HIV-1 strains examined. Two helical segments were predicted in regions displaying profound sequence variation, one in a region suggested to be critical for CD4 binding. The predicted content of helix, β-strand, and coil was consistent with estimates from Fourier transform infrared spectroscopy. The predicted secondary structure of gp120 compared well with data from NMR analysis of synthetic peptides from the V3 loop and the C4 region. As a first step towards modeling the tertiary structure of gp120, the predicted secondary structure may guide the design of future HIV sub-unit vaccine candidates. © 1996 Wiley-Liss, Inc.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/prot.1
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 74
    Digitale Medien
    Digitale Medien
    Constructing amino acid residue substitution classes maximally indicative of local protein structure (1996)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 25 (1996), S. 28-37 
    Details
    ISSN: 0887-3585
    Schlagwort(e): protein evolution ; structure prediction ; information theory ; amino acid substitution ; multiple sequence alignment ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: Using an information theoretic formalism, we optimize classes of amino acid substitution to be maximally indicative of local protein structure. Our statistically-derived classes are loosely identifiable with the heuristic constructions found in previously published work. However, while these other methods provide a more rigid idealization of physicochemically constrained residue substitution, our classes provide substantially more structural information with many fewer parameters. Moreover, these substitution classes are consistent with the paradigmatic view of the sequence-to-structure relationship in globular proteins which holds that the three-dimensional architecture is predominantly determined by the arrangement of hydrophobic and polar side chains with weak constraints on the actual amino acid identities. More specific constraints are imposed on the placement of prolines, glycines, and the charged residues. These substitution classes have been used in highly accurate predictions of residue solvent accessibility. They could also be used in the identification of homologous proteins, the construction and refinement of multiple sequence alignments, and as a means of condensing and codifying the information in multiple sequence alignments for secondary structure prediction and tertiary fold recognition. © 1996 Wiley-Liss, Inc.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/prot.3
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 75
    Digitale Medien
    Digitale Medien
    Study of global motions in proteins by weighted masses molecular dynamics: Adenylate kinase as a test case (1996)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 25 (1996), S. 79-88 
    Details
    ISSN: 0887-3585
    Schlagwort(e): weighted masses ; molecular dynamics ; adenylate kinase ; domain movement ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: The weighted masses molecular dynamics (WMMD) technique is applied to the protein adenylate kinase. A novel set of restraints has been developed to allow the use of this technique with proteins. The WMMD simulation is successful in predicting the flexibility of the two mobile domains of the protein. The end product of the simulation is similar to the known open and AMP bound forms of the enzyme. The biological relevance of the restraints used and potential methods of improving the technique are discussed. © 1996 Wiley-Liss, Inc.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/prot.6
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 76
    Digitale Medien
    Digitale Medien
    The rate-limiting step in the folding of the cis-Pro167Thr mutant of TEM-1 β-lactamase is the trans to cis isomerization of a non-proline peptide bond (1996)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 25 (1996), S. 104-111 
    Details
    ISSN: 0887-3585
    Schlagwort(e): protein folding ; guanidine hydrochloride denaturation ; folding/unfolding kinetics ; cis-trans isomerization ; cis-proline mutant ; cis-non-proline amino acid ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: The stability and kinetics of unfolding and refolding of the P167T mutant of the TEM-1 β-lactamase have been investigated as a function of guanidine hydrochloride concentration. The activity of the mutant enzyme was not significantly modified, which strongly suggests that the Glu166-Thr167 peptide bond, like the Glu166-Pro167, is cis. The mutation, however, led to a significant decrease in the stability of the native state relative to both the thermodynamically stable intermediate and the fully unfolded state of the protein. In contrast to the two slower phases seen in the refolding of the wild-type enzyme, only one phase was detected in the refolding of the mutant, indicating a determining role of proline 167 in the kinetics of folding of the wild-type enzyme. The former phases are replaced by rapid refolding when the enzyme is unfolded for short periods of time, but the latter is independent of the time of unfolding. The monophasic refolding reaction of the mutant is proposed to reflect mainly the trans→cis isomerization of the Glu166-Thr167 peptide bond. © 1996 John Wiley & Sons, Inc.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/prot.8
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 77
    Digitale Medien
    Digitale Medien
    The three-dimensional structure of Escherichia coli porphobilinogen deaminase at 1.76-Å resolution (1996)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 25 (1996), S. 48-78 
    Details
    ISSN: 0887-3585
    Schlagwort(e): prophobilinogen deaminase ; E. coli ; selenomethionine ; X-ray analysis ; tetrapyrrole biosynthesis ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: Porphobilinogen deaminase (PBGD) catalyses the polymerization of four molecules of porphobilinogen to form the 1-hydroxymethylbilane, preuroporphyrinogen, a key intermediate in the biosynthesis of tetrapyrroles. The three-dimensional structure of wild-type PBGD from Escherichia coli has been determined by multiple isomorphous replacement and refined to a crystallographic R-factor of 0.188 at 1.76 Å resolution. The polypeptide chain of PBGD is folded into three α/β domains. Domains 1 and 2 have a similar overall topology, based on a five-stranded, mixed β-sheet. These two domains, which are linked by two hinge segments but otherwise make few direct interactions, form an extensive active site cleft at their interface. Domain 3, an open-faced, anti-parallel sheet of three strands, interacts approximately equally with the other two domains. The dipyrromethane cofactor is covalently attached to a cysteine side-chain borne on a flexible loop of domain 3. The cofactor serves as a primer for the assembly of the tetrapyrrole product and is held within the active site cleft by hydrogen-bonds and salt-bridges that are formed between its acetate and propionate side-groups and the polypeptide chain. The structure of a variant of PBGD, in which the methionines have been replaced with selenomethionines, has also been determined. The cofactor, in the native and functional form of the enzyme, adopts a conformation in which the second pyrrole ring (C2) occupies an internal position in the active site cleft. On oxidation, however, this C2 ring of the cofactor adopts a more external position that may correspond approximately to the site of substrate binding and polypyrrole chain elongation. The side-chain of Asp84 hydrogen-bonds the hydrogen atoms of both cofactor pyrrole nitrogens and also potentially the hydrogen atom of the pyrrole nitrogen of the porphobilinogen molecule bound to the proposed substrate binding site. This group has a key catalytic role, possibly in stabilizing the positive charges that develop on the pyrrole nitrogens during the ring-coupling reactions. Possible mechanisms for the processive elongation of the polypyrrole chain involve: accommodation of the elongating chain within the active site cleft, coupled with shifts in the relative positions of domains 1 and 2 to carry the terminal ring into the appropriate position at the catalytic site; or sequential translocation of the elongating polypyrrole chain, attached to the cofactor on domain 3, through the active site cleft by the progressive movement of domain 3 with respect to domains 1 and 2. Other mechanisms are considered although the amino acid sequence comparisons between PBGDs from all species suggest they share the same three-dimensional structure and mechanism of activity. © 1996 Wiley-Liss, Inc.
    Zusätzliches Material: 16 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/prot.5
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 78
    Digitale Medien
    Digitale Medien
    Crystallization of a family 8 cellulase from Clostridium thermocellum (1996)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 25 (1996), S. 134-136 
    Details
    ISSN: 0887-3585
    Schlagwort(e): family 8 glycohydrolase ; Clostridium thermocellum ; endoglucanase CelA ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: The catalytic domain of cellulase CelA, a family 8 glycohydrolase from C. thermocellum, has been crystallized in the orthorhombic space group P212121 with unit cell dimensions a = 50.12 Å, b = 63.52 Å, c = 104.97 Å. The diffraction pattern extends beyond 1.5 Å resolution. © 1996 Wiley-Liss, Inc.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/prot.12
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 79
    Digitale Medien
    Digitale Medien
    Accessing the Kabat antibody sequence database by computer (1996)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 25 (1996), S. 130-133 
    Details
    ISSN: 0887-3585
    Schlagwort(e): immunoglobulin ; sequence comparison ; cloning ; complementarity determining regions ; alignment ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: The Kabat antibody sequence database has for many years been the primary site for depositing sequence information on antibodies and other proteins of immunological interest. The chief drawback of this database has been that it has only been available in the form of a printed book (Kabat et al., Sequences of Proteins of Immunological Interest, 1991). These data have recently become available on the global computer Internet, but no method of searching the data has, as yet, been provided. Here, the development of a specialized database program for accessing the antibody data is described. This database software has been made accessible over the World Wide Web, together with a program which allows a novel antibody sequence to be tested against the Kabat sequence database, to identify unusual features of an antibody sequence which may represent cloning artifacts or sequencing errors. © 1996 Wiley-Liss, Inc.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/prot.11
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 80
    Digitale Medien
    Digitale Medien
    Crystallization and preliminary crystallographic analysis of RepA1, a replication control protein of the RepFIC replicon of enterotoxin plasmid EntP307 (1996)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 25 (1996), S. 137-138 
    Details
    ISSN: 0887-3585
    Schlagwort(e): antisense RNA ; macroseeding ; cryocrystallography ; DNA replication ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: RepA1 protein is essential for replication of the RepFIC replicon of enterotoxin plasmid EntP307 and is thought to interact directly with the origin of replication. We have purified RepA1 from an over-producing expression system and have prepared single crystals using a macroseeding technique. The crystals belong to space group P212121 or P21212, with cell dimensions a = 61 Å, b = 67 Å, and c = 243 Å. They diffract X-rays to 3.3 Å resolution and probably contain two 40,000 molecular weight RepA1 molecules per asymmetric unit. © 1996 Wiley-Liss, Inc.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/prot.13
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 81
    Digitale Medien
    Digitale Medien
    The surface of β-sheet proteins contains amphiphilic regions which may provide clues about protein folding (1996)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 25 (1996), S. 253-260 
    Details
    ISSN: 0887-3585
    Schlagwort(e): protein structure ; protein folding ; chaperone ; folding path ; amphiphilic sequences ; β-sheet proteins ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: A major bottleneck in the field of biochemistry is our limited understanding of the processes by which a protein folds into its native conformation. Much of the work on this issue has focused on the conserved core of the folded protein. However, one might imagine that a ubiquitous motif for unaided folding or for the recognition of chaperones may involve regions on the surface of the native structure. We explore this possibility by an analysis of the spatial distribution of regions with amphiphilic α-helical potential on the surface of β-sheet proteins.All proteins, Including β-sheet proteins, contain regions with amphiphilic α-helical potential. That is, any α-helix formed by that region would be amphiphilic, having both hydrophobic and hydrophilic surfaces. In the three-dimensional structure of all β-sheet proteins analyzed, we have found a distinct pattern in the spatial distribution of sequences with amphiphilic α-helical potential. The amphiphilic regions occur in ring shaped clusters approximately 20 to 30 Å in diameter on the surface of the protein. In addition, these regions have a strong preference for positively charged amino acids and a lower preference for residues not favorable to α-helix formation. Although the purpose of these amphiphilic regions which are not associated with naturally occurring α-helix is unknown, they may play a critical role in highly conserved processes such as protein folding. © 1996 Wiley-Liss, Inc.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/prot.10
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 82
    Digitale Medien
    Digitale Medien
    The native state of apomyoglobin described by proton NMR spectroscopy: The A-B-G-H interface of wild-type sperm whale apomyoglobin (1996)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 25 (1996), S. 267-285 
    Details
    ISSN: 0887-3585
    Schlagwort(e): myoglobin ; histidine ; hydrophobic core ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: Proton nuclear magnetic resonance spectroscopy was applied to sperm whale apomyoglobin to describe the conformation adopted by the protein under native conditions. The study focused on the A-B-G-H interface, a region known to form a compact subdomain in the apoprotein (Hughson and Baldwin, Biochemistry 28:4415-4422, 1989). Two histidine residues located in this subdomain, His24 and His119, interact and are thought to play a role in the acid denaturation process (Barrick et al., J. Mol. Biol. 237:588-601, 1994). A stable double mutant at these positions (His24Va1/His119Phe sperm whale apomyoglobin) was compared with wild-type apomyoglobin. The amino acid replacements result in chemical shift perturbations near the mutations, in particular in the AB interhelical region, and in a deceleration of backbone amide hydrogen exchange in the B helix from position 27 to position 33. The double mutant data were used to expand and confirm the wild-type spectral analysis. Signals from the D helix were identified that demonstrate the formation of holoprotein-like structure. The assigned wild-type nuclear Overhauser effects, although in small number, were sufficient to construct a model of the compact subdomain of the apoprotein. This was achieved by using the structure of the holoprotein and restraining it with the geometrical information on the apoprotein in a simulated annealing procedure. The experimental restraints define a low-resolution model of the A-B-G-H interface in apomyoglobin. © 1996 Wiley-Liss, Inc.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/prot.1
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 83
    Digitale Medien
    Digitale Medien
    Identification and analysis of long-range electrostatic effects in proteins by computer modeling:Aspartate transcarbamylase (1996)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 25 (1996), S. 300-314 
    Details
    ISSN: 0887-3585
    Schlagwort(e): electrostatic modeling ; Poisson-Boltzmann equation ; finite difference ; multigrid ; allosteric regulation ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: While ion pairs are readily identified in crystal structures, longer range electrostatic interactions cannot be identified from the three-dimensional structure alone. These interactions are likely to be important in large, multisubunit proteins that are regulated by allosteric interactions. In this paper, we show that these interactions are readily detected by electrostatic modeling, using, as an example, unliganded Escherichia coli aspartate transcarbamylase, a widely studied allosteric enzyme with 12 subunits and a molecular weight of 310 kD. The Born, dipolar, and site-site interaction terms of the free energy of protonation of the 810 titratable sites in the holoenzyme were calculated using the multigrid solution of the nonlinear Poisson-Boltzmann equation. Calculated titration curves are in good agreement with experimental titration curves, and the structural asymmetry observed in the crystal structure is readily apparent in the calculated free energies and pK1/2 values. Most of the residues with pK1/2 values that differ substantially from those of model compounds are buried in the low dielectric medium of the protein, particularly at the intersubunit interfaces. The dependence of the site-site interaction free energies on distance is complex, with a steep dependence at distances less than 5 Å and a more shallow dependence at longer distances. Interactions over distances of 6 to 15 Å require a bridging residue and are often not apparent in the structure. The network of interactions between ionizable groups extends across and between subunits and provides a potential mechanism for transmitting long-range structural effects and allosteric signals. © 1996 Wiley-Liss, Inc.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/prot.3
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 84
    Digitale Medien
    Digitale Medien
    The linker of calmodulin lacking Glu84 is elongated in solution, although it is bent in the crystal (1996)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 25 (1996), S. 335-341 
    Details
    ISSN: 0887-3585
    Schlagwort(e): solution X-ray scattering ; calcium-dependent conformational change ; calmodulin-melittin complex ; deviation from crystal structure ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: The solution structure of a mutant calmodulin (des84) lacking Glu84 in the central helix linking the two calmodulin lobes is substantially different from its crystal structure. As determined by small-angle X-ray scattering, the radius of gyration and the maximum linear dimension of des84 in the presence of 0.1 mM calcium are 20.8 Å and 62.5 Å, respectively. These respective dimensions are larger than those expected from the crystal structure of des84, 18.5 Å and 55.0 Å, and smaller than those expected from the crystal structure of wild type, 22.8 Å and 67.5 Å. The distance distribution function of des84 indicates that it assumes an elongated, dumbbell shape in solution. The solution scattering profile of des84 is indistinguishable from that of wild-type calmodulin. The calcium-dependent binding of melittin to des84 causes a change in its shape from elongated to spherical, as seen with other calmodulins. In comparison with calcium-saturated des84, calcium-free des84 is slightly elongated; a slight compaction is observed with native calmodulin. The observed differences between the averaged solution structure and the crystal structure of des84 suggests that an ensemble of structures is available to calmodulin in solution and that its target need not induce a change in its conformation. These results support the theory that the linker region of the central helix of calmodulin functions as a flexible tether. © 1996 Wiley-Liss, Inc.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/prot.5
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 85
    Digitale Medien
    Digitale Medien
    Chemical cross-linking between lysine groups in vimentin oligomers is dependent on local peptide conformations (1996)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 25 (1996), S. 215-224 
    Details
    ISSN: 0887-3585
    Schlagwort(e): α-helix ; β-helix ; β-strand ; coiled coil ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: Previous studies have shown that cytoplasmic intermediate filaments, other than the keratins, are each constructed from a single type of polypeptide chain. Studies involving chemical crosslinking between lysine groups have shown that assembly of the filaments begins with the formation of dimers in which the peptide chains are parallel and in exact register, and that these dimers further associate in antiparallel patterns having specific degrees of overlap. In the present study, molecular modeling of the conformations of vimentin molecules indicated that lysine side chains in identical positions in regions of α-helix in parallel chains might be unable to be linked because they are on opposite sides of the coiled coil hydrophobic core. Examination of published data on chemical crosslinking of lysines in vimentin confirmed that there were no instances of linkage within dimers between the nine pairs of identical lysines that lie more than one position within α-helical regions in parallel chains. Even among linkages that apparently were between dimers, only one of the 11 linkage products identified involved lysines that were both within an α-helical region. In 10 of the 11 identified linkages between dimers, one or both of the linked lysines were in regions of random coil conformation. These results of molecular modeling indicate that relative motion between polypeptide chains in oligomers of intermediate filament proteins is not sufficient to overcome an orientation of lysine groups that is unfavorable for their chemical linkage. This finding supports the interpretations of keratin cross-linking data indicating that parallel homodimers are the basis for keratin intermediate filament assembly. © 1996 Wiley-Liss, Inc.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/prot.7
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 86
    Digitale Medien
    Digitale Medien
    Protein structure and the sequential structure of mRNA: α-Helix and β-sheet signals at the nucleotide level (1996)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 25 (1996), S. 237-252 
    Details
    ISSN: 0887-3585
    Schlagwort(e): cotranslational folding ; protein secondary structure ; ribosome ; reading frame ; neural network ; computer-prediction ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: A direct comparison of experimentally determined protein structures and their corresponding protein coding mRNA sequences has been performed. We examine whether real world data support the hypothesis that clusters of rare codons correlate with the location of structural units in the resulting protein. The degeneracy of the genetic code allows for a biased selection of codons which may control the translational rate of the ribosome, and may thus in vivo have a catalyzing effect on the folding of the polypeptide chain. A complete search for GenBank nucleotide sequences coding for structural entries in the Brookhaven Protein Data Bank produced 719 protein chains with matching mRNA sequence, amino acid sequence, and secondary structure assignment. By neural network analysis, we found strong signals in mRNA sequence regions surrounding helices and sheets. These signals do not originate from the clustering of rare codons, but from the similarity of codons coding for very abundant amino acid residues at the N- and C-termini of helices and sheets. No correlation between the positioning of rare codons and the location of structural units was found. The mRNA signals were also compared with conserved nucleotide features of 16S-like ribosomal RNA sequences and related to mechanisms for maintaining the correct reading frame by the ribosome. © 1996 Wiley-Liss, Inc.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/prot.9
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 87
    Digitale Medien
    Digitale Medien
    Masthead (1996)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 25 (1996) 
    Details
    ISSN: 0887-3585
    Schlagwort(e): Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/prot.340250201
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 88
    Digitale Medien
    Digitale Medien
    Crystallization and preliminary x-ray crystallographic studies of recombinant bovine neurocalcin δ (1996)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 25 (1996), S. 261-264 
    Details
    ISSN: 0887-3585
    Schlagwort(e): X-ray diffraction ; calcium-binding myristoylation ; noncrystallographic symmetry ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: Neurocalcins are novel brain-specific proteins that belong to a new subclass of the EF-hand super-family of calcium binding proteins, defined by the photoreceptor cell-specific protein recoverin (Terasawa et al., J. Biol. Chem. 267:19596-19599, 1992). Here we report the purification and crystallization of unmyristoylated recombinant bovine neurocalcin δ from Escherichia coli. Crystals of a bovine neurocalcin δ have been grown by macro-seeding at room temperature through vapor phase equilibration using the hanging drop technique with ammonium sulfate as the precipitating agent. The crystals diffract to at least 2.5 Å resolution and belong to monoclinic space group P2I with unit cell dimensions a = 42.734 Å, b = 94.343 Å, c = 50.696 Å, and β = 98.37°. The asymmetric unit contains two molecules, with corresponding crystal volume per protein mass (Vm) of 2.29 Å3/Da and solvent fraction of 45% by volume, exhibiting an approximate 222 point symmetry. © 1996 Wiley-Liss, Inc.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/prot.11
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 89
    Digitale Medien
    Digitale Medien
    Folding simulations and computer redesign of protein A three-helix bundle motifs (1996)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 25 (1996), S. 286-299 
    Details
    ISSN: 0887-3585
    Schlagwort(e): lattice model of proteins ; Monte Carlo method ; mirror image fold ; multiple mutations ; hydrophobic core repacking ; turn handedness modification ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: In solution, the B domain of protein A from Staphylococcus aureus (B domain) possesses a three-helix bundle structure. This simple motif has been previously reproduced by Kolinski and Skolnick (Proteins 18: 353-366, 1994) using a reduced representation lattice model of proteins with a statistical interaction scheme. In this paper, an improved version of the potential has been used, and the robustness of this result has been tested by folding from the random state a set of three-helix bundle proteins that are highly homologous to the B domain of protein A. Furthermore, an attempt to redesign the B domain native structure to its topological mirror image fold has been made by multiple mutations of the hydrophobic core and the turn region between helices I and II. A sieve method for scanning a large set of mutations to search for this desired property has been proposed. It has been shown that mutations of native B domain hydrophobic core do not introduce significant changes in the protein motif. Mutations in the turn region were also very conservative; nevertheless, a few mutants acquired the desired topological mirror image motif. A set of all atom models of the most probable mutant was reconstructed from the reduced models and refined using a molecular dynamics algorithm in the presence of water. The packing of all atom structures obtained corroborates the lattice model results. We conclude that the change in the handedness of the turn induced by the mutations, augmented by the repacking of hydrophobic core and the additional burial of the second helix N-cap side chain, are responsible for the predicted preferential adoption of the mirror image structure. © 1996 Wiley-Liss, Inc.
    Zusätzliches Material: 15 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/prot.2
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 90
    Digitale Medien
    Digitale Medien
    The application of different solvation and electrostatic models in molecular dynamics simulations of ubiquitin: How well is the x-ray structure “maintained”? (1996)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 25 (1996), S. 315-334 
    Details
    ISSN: 0887-3585
    Schlagwort(e): particle mesh Ewald ; cutoff ; periodic box ; shell ; root mean square deviation ; atomic fluctuation ; order parameters ; force field ; aqueous solution ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: We present molecular dynamics simulations on ubiquitin with explicit solvent molecules and investigate the influence of different force fields [Weiner et al. (J. Am. Chem. Soc. 106:765-784, 1984; J. Comput. Chem. 7:230-252, 1986) vs. Cornell et al. (J. Am. Chem. Soc. 117:5179-5197, 1995)], different treatments of the long-range electrostatic interaction (8 Å cutoff vs. particle mesh Ewald), and different solvation models (periodic box vs. small shell of water molecules) on the structure and the dynamics of the protein. Structural data are monitored by atomic root mean square deviations (RMSDs) from the crystal structure, the radius of gyration, the solvent-accessible surface area, and the pattern of the backbone hydrogen bonds. The dynamic behavior is assessed by the atomic fluctuations and the order parameters of the N-H backbone vectors.With the Cornell et al. force field and a periodic box model, the simulated structures stay much closer to the experimental X-ray structure than with the older Weiner et al. force field. A further improvement of the simulation is found when the electrostatic interaction is evaluated with the particle mesh Ewald method; after 1.2 ns of simulation the backbone RMSD amounts to only 1.13 Å. The analysis of the dynamic parameters shows that this good structural agreement is not due to a damping of internal motion in the protein.For a given length of simulation time, the shell models achieve an agreement between simulated and experimental structures that is comparable to the best models that employ a periodic box of solvent models. However, compared with the box models, the fluctuations of the protein atoms in the shell models are smaller, and only with simulation times as long as 2 ns do they become of comparable size to the experimental ones. © 1996 Wiley-Liss, Inc.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/prot.4
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 91
    Digitale Medien
    Digitale Medien
    Exploring the energy landscapes of molecular recognition by a genetic algorithm: Analysis of the requirements for robust docking of HIV-1 protease and FKBP-12 complexes (1996)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 25 (1996), S. 342-353 
    Details
    ISSN: 0887-3585
    Schlagwort(e): structure-based drug design ; ligand-protein recognition ; binding landscapes ; docking funnels ; stochastic search ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: Energy landscapes of molecular recognition are explored by performing “semi-rigid” docking of FK-506 and rapamycin with the Fukisawa binding protein (FKBP-12), and flexible docking simulations of the Ro-31-8959 and AG-1284 inhibitors with HIV-1 protease by a genetic algorithm. The requirements of a molecular recognition model to meet thermodynamic and kinetic criteria of ligand-protein docking simultaneously are investigated using a family of simple molecular recognition energy functions. The critical factor that determines the success rate in predicting the structure of ligand-protein complexes is found to be the roughness of the binding energy landscape, in accordance with a minimal frustration principle. The results suggest that further progress in structure prediction of ligand-protein complexes can be achieved by designing molecular recognition energy functions that generate binding landscapes with reduced frustration. © 1996 Wiley-Liss, Inc.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/prot.6
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 92
    Digitale Medien
    Digitale Medien
    The influence of a protein on water dynamics in its vicinity investigated by molecular dynamics simulation (1996)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 25 (1996), S. 366-378 
    Details
    ISSN: 0887-3585
    Schlagwort(e): hydration/solvation ; Kohlrausch-Williams-Watts relaxation ; diffusion ; residence time ; Voronoi polyhedra ; ubiquitin ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: A system containing the globular protein ubiquitin and 4,197 water molecules has been used for the analysis of the influence exerted by a protein on solvent dynamics in its vicinity. Using Voronoi polyhedra, the solvent has been divided into three subsets, i.e., the first and second hydration shell, and the remaining bulk, which is hardly affected by the protein. Translational motion in the first shell is retarded by a factor of 3 in comparison to bulk. Several molecules in the first shell do not reach the diffusive regime within 100 ps. Shell-averaged orientational autocorrelation functions, which are also subject to a retardation effect, cannot be modeled by a single exponential time law, but are instead well-described by a Kohlrausch-Williams-Watts (KWW) function. The underlying distribution of single-molecule rotational correlation times is both obtained directly from the simulation and derived theoretically. The temperature dependence of reorientation is characterized by a strongly varying correlation time, but a virtually temperature-independent KWW exponent. Thus, the coupling of water structure relaxation with the respective environment, which is characteristic of each solvation shell, is hardly affected by temperature. In other words, the functional form of the distributions of single-molecule rotational correlation times is not subject to a temperature effect. On average, a correlation between reorientation and lifetimes of neighborhood relations is observed. © 1996 Wiley-Liss, Inc.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/prot.8
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 93
    Digitale Medien
    Digitale Medien
    Adjusting potential energy functions for lattice models of chain molecules (1996)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 25 (1996), S. 379-388 
    Details
    ISSN: 0887-3585
    Schlagwort(e): protein modeling ; lattice approximation error ; adjusting of energy functions ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: Lattice models of proteins can approximate off-lattice structures to arbitrary precision with RMS (root mean squared) deviations roughly equal to half the lattice spacing (Rykunov et al., Proteins 22:100-109, 1995; Reva et al., J. Comp. Biol., 1996). However, even small distortions in the positions of chain links lead to significant errors in lattice-based energy calculations (Reva et al., J. Comp. Chem., 1996). These errors arise mainly from rigid interactions (such as steric repulsion) which change their energies considerably at a range which is much smaller than the usual accuracy of lattice modeling (〉1.0 Å). To reduce this error, we suggest a procedure of adjusting energy functions to a given lattice. The general approach is illustrated with energy calculations based on pairwise potentials by Kolinski et al. (J. Chem. Phys. 98:1-14, 1993). At all the lattice spacings, from 0.5-3.8 Å, the lattice-adjusted potentials improve the accuracy of lattice-based energy calculations and Increase the correlations between off-lattice and lattice energies. © 1996 Wiley-Liss, Inc.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/prot.9
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 94
    Digitale Medien
    Digitale Medien
    Building self-avoiding lattice models of proteins using a self-consistent field optimization (1996)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 26 (1996), S. 1-8 
    Details
    ISSN: 0887-3585
    Schlagwort(e): lattice models of proteins ; self-consistent field optimization ; self-avoiding ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: We present an algorithm to build self-avoiding lattice models of chain molecules with low RMS deviation from their actual 3D structures. To find the optimal coordinates for the lattice chain model, we minimize a function that consists of three terms: (1) the sum of squared deviations of link coordinates on a lattice from their off-lattice values, (2) the sum of “short-range” terms, penalizing violation of chain connectivity, and (3) the sum of “long-range” repulsive terms, penalizing chain self-intersections. We treat this function as a chain molecule “energy” and minimize it using self-consistent field (SCF) theory to represent the pairwise link repulsions as 3D fields acting on the links. The statistical mechanics of chain molecules enables computation of the chain distribution in this field on the lattice. The field is refined by iteration to become self-consistent with the chain distribution, then dynamic programming is used to find the optimal lattice model as the “lowest-energy” chain pathway in this SCF. We have tested the method on one of the coarsest (and most difficult) lattices used for model building on proteins of all structural types and show that the method is adequate for building self-avoiding models of proteins with low RMS deviations from the actual structures. © 1996 Wiley-Liss, Inc.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
  • 95
    Digitale Medien
    Digitale Medien
    Computational simulations of stem-cell factor/c-Kit receptor interaction (1996)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 26 (1996), S. 42-54 
    Details
    ISSN: 0887-3585
    Schlagwort(e): cell surface receptors ; hematopoietic factors ; cytokines ; structure prediction ; homology modeling ; molecular dynamics ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: Stem-cell factor (SCF) is a noncovalent homodimeric cytokine that exhibits profound biological function in the early stages of hematopoiesis by binding to a cell surface tyrosine kinase receptor that is encoded by the c-Kit proto-oncogene. The results obtained from a combined implementation of homology-based molecular modeling and computational simulations in the study of species-specific SCF/c-Kit interactions are reported. The structural models of the human and rat SCF ligands are based on the close structural similarity to the cytokine M-CSF, whose Cα structure has recently become available. The constant domains of the human Fc fragment are used as a template for the ligand binding domains of the c-Kit receptor. The factors responsible for the stabilization of the SCF quaternary structure and the molecular determinants for ligand recognition and ligand specificity have been identified by assessing the conformational, topographical, and dynamic features of the isolated ligands and of the ligand-receptor complexes. © 1996 Wiley-Liss, Inc.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
  • 96
    Digitale Medien
    Digitale Medien
    Electrostatic properties deduced from refined structures of NADH-cytochrome b5 reductase and the other flavin-dependent reductases: Pyridine nucleotide-binding and interaction with an electron-transfer partner (1996)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 26 (1996), S. 32-41 
    Details
    ISSN: 0887-3585
    Schlagwort(e): α/β structure ; β barrel ; electrostatic potential ; flavin adenine dinucleotide ; flavin mononucleotide ; pyridine nucleotide ; structure refinement ; x-ray crystallography ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: Electrostatic properties on the protein surface were examined on the basis of the crystal structure of NADH-cytochrome b5 reductase refined to a crystallographic R factor of 0.223 at 2.1 Å resolution and of the other three flavin-dependent reductases. A structural comparison of NADH-cytochrome b5 reductase with the other flavin-dependent reductases, ferredoxin-NADP+ reductase, phthalate dioxygenase reductase, and nitrate reductase, showed that the α/β structure is the common motif for binding pyridine nucleotide. Although the amino acid residues associated with pyridine nucleotide-binding are not conserved, the electrostatic properties and the location of the pyridine nucleotide-binding pockets of NADH-requiring reductases were similar to each other. The electrostatic potential of the surface near the flavin-protruding side (dimethylbenzene end of the flavin ring) of NADH-cytochrome b5 reductase was positive over a wide area while that of the surface near the heme-binding site of cytochrome b5 was negative. This implied that the flavin-protruding side of NADH-cytochrome b5 reductase is suitable for interacting with its electron-transfer partner, cytochrome b5. This positive potential area is conserved among four flavin-dependent reductases. A comparison of the electron-transfer partners of four flavin-dependent reductases showed that there are significant differences in the distribution of electrostatic potential between inter-molecular and inter-domain electron-transfer reactions. © 1996 Wiley-Liss, Inc.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
  • 97
    Digitale Medien
    Digitale Medien
    Structural stability of disulfide mutants of basic pancreatic trypsin inhibitor: A molecular dynamics study (1996)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 26 (1996), S. 66-71 
    Details
    ISSN: 0887-3585
    Schlagwort(e): BPTI ; folding ; unfolding ; disulfide ; molecular dynamics ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: The structure and folding of basic pancreatic trypsin inhibitor (BPTI) has been studied extensively by experimental means. We report a computer simulation study of the structural stability of various disulfide mutants of BPTI, involving eight 250-psec molecular dynamics simulations of the proteins in water, with and without a phosphate counterion. The presence of the latter alters the relative stability of the single disulfide species [5-55] and [30-51]. This conclusion can explain results of mutational studies and the conservation of residues in homologues of BPTI, and suggests a possible role of ions in stabilizing one intermediate over another in unfolding or folding processes. © 1996 Wiley-Liss, Inc.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
  • 98
    Digitale Medien
    Digitale Medien
    Masthead (1996)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 26 (1996) 
    Details
    ISSN: 0887-3585
    Schlagwort(e): Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/prot.340260101
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 99
    Digitale Medien
    Digitale Medien
    No crystals no grant (1996)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 26 (1996), S. i 
    Details
    ISSN: 0887-3585
    Schlagwort(e): Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: No Abstracts.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/prot.340260102
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 100
    Digitale Medien
    Digitale Medien
    Patent history (1996)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 26 (1996), S. i 
    Details
    ISSN: 0887-3585
    Schlagwort(e): Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: No abstract.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
Schließen ⊗
Diese Webseite nutzt Cookies und das Analyse-Tool Matomo. Weitere Informationen finden Sie hier...