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  • 1985-1989  (3,759)
  • 1965-1969  (3,069)
  • 1986  (3,759)
  • 1966  (1,474)
  • 1965  (1,595)
  • Polymer and Materials Science  (6,381)
  • Computational Chemistry and Molecular Modeling  (411)
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  • 1985-1989  (3,759)
  • 1965-1969  (3,069)
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  • 1
    Electronic Resource
    Electronic Resource
    Regional morphology and biochemistry in experimental brain abscesses (1986)
    Springer
    Acta neuropathologica 69 (1986), S. 17-22 
    Details
    ISSN: 1432-0533
    Keywords: Brain abscess ; Cat ; Energy state ; Substrate mapping
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Brain abscesses were induced experimentally in six cats by stereotactic inoculation ofStaphylococcus aureus A8 into the white matter of the left cerebral hemisphere. Seven days later, the brains were frozen in situ with liquid nitrogen and subsequently sawn into coronal sections of 5 mm thickness, while being cooled with liquid nitrogen. Thin slices were taken from those sections containing the largest expanse of abscess: slices of 5 μm thickness were stained histologically, and in adjacent 20 μm slices the regional distribution of ATP and glucose was mapped using substrate-specific bioluminescence methods. Furthermore, the NADH fluorescence from the surface of the tissue section was recorded. Six layers could be distinguished histologically in the abscess capsule, five of which showed different substrate patterns. Only in two layers a low metabolic activity could be observed, as shown by slight ATP bioluminescence. The pattern of the biochemical substrates in the white matter surrounding the abscess indicated a reduction in the cellular oxygen availability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00687033
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  • 2
    Electronic Resource
    Electronic Resource
    Topographic distribution of callosal neurons and terminals in the cerebral cortex of the cat (1986)
    Springer
    Anatomy and embryology 173 (1986), S. 323-342 
    Details
    ISSN: 1432-0568
    Keywords: Cerebral cortex ; Corpus callosum ; Anterior commissure ; Columns ; Horseradish peroxidase ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary This investigation had four goals: First, to study the general topography of the corpus callosum (CC) of the cat. Second, to study the columnar organization of CC terminals and map their banding pattern in the cortex. Third, to examine the relation between CC neuron density and the presence of CC terminal columns. Fourth, to determine whether CC and anterior commissure (AC) neuron distributions are intermixed. Eight adult cats were subjected to partial commissurotomies, and then to large injections of horseradish peroxidase to one cerebral hemisphere. Processing with tetramethyl benzidine revealed retrogradely labelled cells and anterogradely labelled terminals in the cortex of the uninjected hemisphere. The distributions of these cells and terminals were examined by light microscopy and analyzed by computer microscopic methods. The genu of the CC interconnects frontal portions of the cortex, the body interconnects mostly dorsal portions of the cortex, while the splenium interconnects the temporal and occipital cortices. Reconstructions of the CC terminal columns reveal intricate banding patterns in several non-primary areas of the cortex. CC cell density is greater within than outside the terminal columns. CC and AC neurons intermix in the infragranular lavers of the neocortex.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00318916
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  • 3
    Electronic Resource
    Electronic Resource
    Is motilin a cerebellar peptide in the rat? (1986)
    Springer
    Anatomy and embryology 173 (1986), S. 371-376 
    Details
    ISSN: 1432-0568
    Keywords: Motilin-like immunoreactivity ; RIA ; HPLC ; Cat ; Intestine ; Rat ; Cerebellum ; Purkinje cells ; Dendrites ; Neocortex ; Pyramidal cells ; Hippocampus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Motilin was demonstrated by the immunoperoxidase technique in endocrine cells of the gastrointestinal tract using several specific antisera. Motilin-like immunoreactivity could only be demonstrated with one of these antisera and was observed in Purkinje cells and dendrites of the cerebellum, in pyramidal cells and dendrites of the cerebral cortex and in dendrites of the CA3 field of the hippocampus of the rat. Very low motilin-like immunoreactivity was found in cerebellum as well as in cerebral cortex using radioimmunoassay. However, using reverse phase liquid chromatography combined with UV-detection and radioimmunoassay, no peak of a peptide corresponding to synthetic motilin was detectable in rat cerebellar extracts, in contrast to findings in rat duodenum. The results do not suggest that motilin is an intrinsic neuroactive substance of the cerebellum.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00318921
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  • 4
    Electronic Resource
    Electronic Resource
    Afferents to the lateral reticular nucleus from the oculomotor region (1986)
    Springer
    Anatomy and embryology 175 (1986), S. 261-269 
    Details
    ISSN: 1432-0568
    Keywords: Lateral reticular nucleus ; Edinger-Westphal nucleus ; Retrograde transport of WGA-HRP ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary By means of retrograde axonal transport of the wheat germ agglutinin — horseradish peroxidase complex, a projection from the Edinger-Westphal nucleus to the lateral reticular nucleus was demonstrated in the cat. Following small tracer ejections in the main part of the lateral reticular nucleus, a significant number of labelled neurons were found bilaterally throughout the Edinger-Westphal nucleus. Most of the labelled cells were located on the ipsilateral side. The projecting neurons are spindle-shaped to round with a maximum diameter of the cell body between 15 and 30 μm. The findings are discussed in relation to other Edinger-Westphal efferent projections, and some comments are made concerning the cytoarchitecture and delineation of the feline Edinger-Westphal nucleus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00389604
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  • 5
    Electronic Resource
    Electronic Resource
    Fluorescent double-labelling study of ascending and descending neurones in the feline lateral cervical nucleus (1986)
    Springer
    Experimental brain research 62 (1986), S. 479-485 
    Details
    ISSN: 1432-1106
    Keywords: Cat ; Double labelling ; Fluorescent tracing ; Lateral cervical nucleus ; Ascending and descending neurones
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The organization of ascending and descending neurones of the lateral cervical nucleus (LCN) was investigated in 10 adult cats after injections of the fluorescent tracers Fast Blue and Nuclear Yellow. Injections into the thalamus and tectum resulted in up to 3000 labelled cell profiles within the contralateral LCN. This corresponded to a calculated number of 4500 labelled LCN neurones. The greatest diameter of the labelled cell profiles was about 30 μm. They were located throughout the nucleus, but were less numerous in its medial portion. Injections mainly into the dorsal horn of different pairs of cervical and lumbar segments of the spinal cord resulted in a calculated number of up to 305 labelled LCN cells. The diameter of these cell profiles was about 25 μm and they were mainly situated in the rostro-ventral and medial parts of the LCN. Doublelabelled cells with ascending and descending projections were not encountered after injections into the thalamus-tectum and spinal segments C5-6. About 15% of the descending LCN cells were doublelabelled by pairs of spinal injections separated by intervals of one segment. It is concluded that the neurones descending down the spinal cord and ascending to the thalamus-tectum constitute different subpopulations of cells within the LCN and that a minor proportion of the descending cells seem to project to at least three adjacent segments of the spinal cord.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00236026
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  • 6
    Electronic Resource
    Electronic Resource
    Short latency inputs to phrenic motoneurones from the sensorimotor cortex in the cat (1986)
    Springer
    Experimental brain research 61 (1986), S. 280-290 
    Details
    ISSN: 1432-1106
    Keywords: Cerebral cortex ; Phrenic nerve ; Phrenic motoneurones ; Medullary pyramids ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Short latency responses were recorded from C5 phrenic roots and intracellularly from phrenic motoneurones following stimulation of the pericruciate cortex or medullary pyramids in cats anaesthetized with Nembutal or chloralose-urethane. Focal stimulation of the cortical surface (single pulses, 0.5–2 ms, 0.3–8 mA) during inspiration evoked EPSPs (latency 4.7 ± 1.7 ms, rise time 1.9 ± 1.1 ms, amplitude 0.22 to 3.94 mV) in 42% of motoneurones studied (n = 107). The EPSPs were absent, or on average 60% smaller, following stimulation during expiration. In all but two motoneurones, during both inspiration and expiration, hyperpolarizing potentials were observed either following the initial depolarization or alone. They could be reversed by hyperpolarizing current or chloride injection. Stimulation of the pyramidal tract at mid medullary level (1 to 3 pulses, 0.2 ms) evoked short latency excitation in phrenic motoneurones only with currents of more than 200 μA. Smaller stimuli applied to the medial reticular formation above the pyramidal tract evoked excitation (onset latency 1.5–3.2 ms) in which the earliest part was probably monosynaptic. These results show that the corticospinal responses in phrenic motoneurones are both excitatory and inhibitory. They are not transmitted through the pyramidal tract and are at least disynaptic. Excitation evoked from the medullary pyramidal tract can be explained by current spread beyond the pyramidal tract fibres.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00239518
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  • 7
    Electronic Resource
    Electronic Resource
    Development of horizontal intrinsic connections in cat striate cortex (1986)
    Springer
    Experimental brain research 63 (1986), S. 443-448 
    Details
    ISSN: 1432-1106
    Keywords: Visual cortex (area 17) ; Intrinsic connections ; Visual deprivation ; Development ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Intracortical injections of horseradish peroxidase conjugated with wheat-germ agglutinin (WGA-HRP) reveal a characteristic patchy staining pattern within the superficial layers of cat striate cortex. The patches consist of a dense accumulation of labeled neurons and axonal arborizations. We have investigated the tangential organization and the development of these intrinsic cortical connections by using a flat-mount preparation of area 17. The diameter of the patches varied from 200 to 400 μm, the center-to-center distance ranged from 400 to 800 μm, and the spread of patches extended further in the anterior-posterior than in the medial-lateral direction. The expression of these horizontal patchy connections is age- and experience-dependent. From ten days to six weeks of age patches are exuberant and on occasion fuse to beaded bands extending radially from the injection site. From 6 weeks onwards the number and the tangential spread of the patches decreases to one or two rows of isolated clusters. Long-term binocular deprivation disrupts this pattern of intrinsic connections nearly completely. We infer from these results that there is an inborn pattern of discrete horizontal connections in striate cortex which is shaped by visual experience and requires contour vision for its maintenance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00236865
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  • 8
    Electronic Resource
    Electronic Resource
    Excitatory interactions between phrenic motoneurons in the cat (1986)
    Springer
    Experimental brain research 62 (1986), S. 273-280 
    Details
    ISSN: 1432-1106
    Keywords: Motoneurons ; Interactions ; Cholinergic synapses ; Phrenic nerve ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 1. Interactions between phrenic motoneurons have been analysed in anaesthetized, paralyzed cats after C3 to C7 deafferentation. Effects of electrical stimulation of the C5 phrenic axons have been studied on thin filaments dissected from the stimulated nerve. Repetitive stimulation could elicit, after the primary direct response of the stimulated axons, a secondary response named Recurrent Response, RR. 2. RRs have been obtained in 117/186 phrenic axons. They appear sporadically (mean occurrence: 3.75 RRs elicited by 100 shocks of stimulation) at a constant latency. They originate from a spinal mechanism since they persist after C2 transection and disappear after section of the ventral roots. 3. The mechanism responsible for RR shows spatial and temporal facilitation. The RR probability increases with the number of antidromically invaded motoneurons as revealed by changes either of stimulation intensity or of central respiratory drive. However, RR could be evoked in a motoneuron without an antidromic volley in its axon. 4. Systemic injections of nicotinic blocking drugs such as dihydro-β-erytroidin or mecamylamine decrease or suppress the occurrence of RR; therefore, cholinergic synapses are involved in the RR generating process. 5. RR are assumed to be due to direct excitatory interactions between homonymous motoneurons. Recurrent axon collaterals impinging directly on neighbouring motoneurons would link together the different motoneurons of the phrenic pool. The functional significance of this phenomenon is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00238846
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  • 9
    Electronic Resource
    Electronic Resource
    Dual mode of projections from the parietal to the motor cortex in the cat (1986)
    Springer
    Experimental brain research 62 (1986), S. 281-292 
    Details
    ISSN: 1432-1106
    Keywords: PT cell ; Areas 4γ and 5 ; Intracortical microstimulation ; HRP ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 1. The cortico-cortical projection from area 5 to area 4 γ was studied in anesthetized cats. 2. Intracortical microstimulation of area 5 produced EPSPs in pyramidal tract (PT) cells in area 4 γ. Such EPSPs were analysed in a total of 54 fast PT cells. The rising phase of these EPSPs was often composed of fast and slow components. 3. Fast-rising EPSPs (fast component) were produced predominantly by stimulation within layer III of area 5 while slow-rising EPSPs (slow component) were evoked predominantly by stimulation within layer V of area 5. 4. The amplitudes of the fast and slow components of EPSPs produced during repetitive stimulation within layers III and V of area 5 decreased and increased, respectively, with an increase in the stimulus frequency without any appreciable changes in their latency and time-to-peak. The slow component was much less influenced by membrane hyperpolarization than the fast component. 5. Retrogradely labeled neurons were found not only in layer III but also in layer V of area 5 following HRP injection centered on superficial layers (I–III) of area 4γ. 6. It is suggested that there are two groups of cortico-cortical neurons in layers III and V of area 5, which may make monosynaptic contact with the proximal and distal sites of fast PT cells in area 4γ, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00238847
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  • 10
    Electronic Resource
    Electronic Resource
    Pattern of pyramidal tract collateralization to medial thalamus, lateral hypothalamus and red nucleus in the cat (1986)
    Springer
    Experimental brain research 61 (1986), S. 585-596 
    Details
    ISSN: 1432-1106
    Keywords: Cat ; Chloralose ; Motor cortex ; PT collaterals ; Macro- and microstimulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Stimulating electrodes were placed in the red nucleus, lateral hypothalamus and medial thalamus in order to determine whether pyramidal tract (PT) neurons send collaterals to those sites. The red nucleus projections are well-known, but it was discovered that PT neurons also project into the other two sites. All of the fibers that sent collaterals to all three sites originated from fast PT neurons. Those that responded to stimulation of the skin and that sent collaterals to two or three sites were predominantly fast PT neurons. Those neurons that responded only to cerebral peduncle stimulation were predominantly slowly-conducting, when compared with the set of PT neurons in response to cerebral peduncle stimulation. The patterns of collateral branching to red nucleus and to lateral hypothalamus were similar, suggestimg a similar synaptic effect of the pyramidal system in the two sites. Measurement of the speed of conduction from three sites along the length of corticospinal fibers revealed large changes on some, but not all, fibers; there was no evident pattern to these changes that might be associated with collateral branching. A new hypothesis concerning the functional role of fast PT neurons in regulating movement is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00237585
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  • 11
    Electronic Resource
    Electronic Resource
    An electrophysiological investigation of propriospinal inspiratory neurons in the upper cervical cord of the cat (1986)
    Springer
    Experimental brain research 61 (1986), S. 625-637 
    Details
    ISSN: 1432-1106
    Keywords: Respiratory neurons ; Cervical spinal cord ; Axonal projection ; Phrenic motoneurons ; Intercostal motoneurons ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary This study was performed in order to describe the location, axonal projection and possible synaptic action of the inspiratory neurons recently described in the upper cervical cord. In 26 cats anaesthetized with Nembutal, extracellular recordings were made from 224 cervical inspiratory units which were found near the lateral border of lamina VII and formed a column extending from the caudal end of the nucleus retroambigualis at the C1 segment to the rostral half of the C3 segment. Most of the units (approximately 85%) could be excited antidromically from the thoracic cord. Antidromic mapping showed collateral branches to the C5 segment in the vicinity of the phrenic nucleus, occasionally crossing the midline. No synaptic connections with phrenic motoneurones could be revealed either by cross-correlation of the activity of the cervical units with the discharge of C5 phrenic root, or by spike-triggered averaging (STA) of the post-synaptic noise recorded intracellularly from phrenic motoneurons. Extensive branching was found in the examined T3–T5 segments with arborizations near the ipsilateral intercostal motor nuclei and often extending across the midline. Cross-correlation experiments did not show clear monosynaptic connections to the inspiratory intercostal motoneurons. Intracellular recording from intercostal motoneurons and STA resulted in a few (2 out of 37) small, probably disynaptic, e.p.s.p.s. It is concluded that the upper cervical neurons are involved in the control of phrenic and intercostal motoneurons, probably through a disynaptic pathway involving segmental interneurons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00237589
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  • 12
    Electronic Resource
    Electronic Resource
    Anti-5-hydroxytryptamine antibodies: studies on their cross-reactivity in vitro and their immunohistochemical specificity (1986)
    Springer
    Experimental brain research 63 (1986), S. 627-638 
    Details
    ISSN: 1432-1106
    Keywords: Antibodies to serotonin ; Immunocytochemistry ; Radioimmunoassay ; Antibodies specificity ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Antibodies to 5-hydroxytryptamine (5-HT) were obtained from 4 rabbits after injections of 5-HT coupled to bovine serum albumin by means of paraformaldehyde (PF). Two methods were used to monitor the developement of antibodies (AB): the one based on the “in vitro” competitive binding properties of the antibodies with3(H)5-HT, the other, on their “in situ” binding properties to endogenous 5-HT, using the peroxidase-anti-peroxidase immunohistochemical technique, applied to paraffin embedded sections of cat brainstem. No pharmacological processing, detergents or proteolytic enzymes were used. The specificity of the antiserum was tested by competitive procedures with 20 analogs using the “in vitro” and “in situ” techniques. “In vitro” studies were performed with 5-HT free analogs and with analogs previously coupled with PF to lysine. Radioimmunological tests showed that the antibodies recognize mainly the ethylamine (CH2-CH2-NH2)-cham of the free analogs and that the best specificity was obtained with the 5-HT conjugate (5-HT-lysine-PF). The results suggest that the hapten is coupled through the phenolic positions C4 or C5. The “in situ” immunohistochemical extinction assays also revealed a distinct specificity for 5-HT. Possible optical and ultrastructural applications are illustrated in the raphé nuclei of the cat. These results confirm the reliability of radioimmunological tests for studying the specificity of AB directed against haptens, provided that haptens and analogs tested were first chemically transformed to resemble the immunogen (herewith lysine-PF coupling) with regard to its antigenic structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00237485
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  • 13
    Electronic Resource
    Electronic Resource
    Liminal and supraliminal response characteristics of mechanoreceptive neurons in the cuneate nucleus of cat (1986)
    Springer
    Experimental brain research 62 (1986), S. 486-494 
    Details
    ISSN: 1432-1106
    Keywords: Mechanoreceptors ; Thresholds ; Stimulus-response functions ; Cuneatus ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The response characteristics of mechanoreceptive neurons (RA, SA, and PC) innervating the foot pad of cat were determined in the cuneate nucleus. The mechanical stimuli were single sinusoidal pulses of varying frequency (20, 60, 150, and 240 Hz), and vibratory trains of varying frequency (80 and 240 Hz) and duration (50, 100, and 400 ms). Thresholds and stimulus-response functions were determined with single pulses. Absolute thresholds (1 impulse/train), tuning thresholds (1 impulse/cycle), and atonal intervals (the range between absolute and tuning thresholds) were determined with vibratory stimulus trains. When tested with single pulses the thresholds resembled those of primary afferents in all unit populations. The stimulus-response function of PC units but not of all RA units were comparable to those of primary afferents. Noxious conditioning stimulation did not influence the thresholds of cuneate mechanoreceptors in the tested sample (N = 6). Mostly PC units were tested with vibratory trains. Absolute thresholds were not dependent on stimulus duration, which is a consistent finding with peripheral units. In contrast to peripheral units, the tuning thresholds in most PC units were elevated with increasing stimulus duration. The variability in the range of atonal intervals was much larger than in the periphery. Thus, it seems that both the type of the tactile signal and the type of the studied mechanoreceptive neuron are critical parameters in determining whether the response characteristics of neurons in the cuneate and in the periphery are identical or not.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00236027
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  • 14
    Electronic Resource
    Electronic Resource
    Auditory response properties of neurons in the claustrum and putamen of the cat (1986)
    Springer
    Experimental brain research 61 (1986), S. 432-437 
    Details
    ISSN: 1432-1106
    Keywords: Claustrum ; Putamen ; Auditory response properties ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The auditory response properties of single neurons in claustrum and putamen were studied in response to simple dichotic stimuli (viz. noise- and tone-bursts) in chloralose-anaesthetized cats. Neurons in claustrum were commonly weakly driven with long latency, were broadly tuned and were excited by stimulation of either ear (EE). Putamen neurons, in contrast, were securely driven with short latency, showed irregular tuning with a preference for low frequencies and were either EE or excited only by the contralateral ear (EO). The differences between claustrum and putamen responses can be related to differences in connections with the auditory cortical fields and with auditory thalamus. Some neurons were also tested for visual responsiveness: auditory and visual cells were intermingled in both nuclei and only a small percentage of cells were bimodal. In contrast to the visual and somatosensory input to claustrum, which are derived from primary cortical fields, the auditory input to claustrum is apparently derived from non-primary cortical regions, suggesting a fundamentally different role for processing of auditory information in claustrum.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00239531
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  • 15
    Electronic Resource
    Electronic Resource
    Eye position signals in cat superior colliculus (1986)
    Springer
    Experimental brain research 61 (1986), S. 447-450 
    Details
    ISSN: 1432-1106
    Keywords: Superior colliculus ; Single units ; Eye movements ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Single unit activity was studied in the intermediate and deep layers of the superior colliculus in two trained cats. Eye movements were recorded with a magnetic search coil, the head being fixed. Discharge rates which varied as a function of eye position were consistently observed in 7 of 67 (about 10%) of the sample of eye movement-related units. These units showed similar changes in firing rate as a function of eye position in total darkness and during task related fixation of visual targets and thus appear to convey an “eye position” signal. Their activity may originate either from proprioception or from corollary discharge.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00239534
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  • 16
    Electronic Resource
    Electronic Resource
    Binocular suppression in cortical neurons (1986)
    Springer
    Experimental brain research 63 (1986), S. 581-584 
    Details
    ISSN: 1432-1106
    Keywords: Visual neurons ; Contrast ; Binocular interactions ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Dichoptic presentation of patterns similar in shape but of very different contrast results in the perception of only the high contrast pattern (binocular suppression). When recording from binocular neurons of the cat visual cortex, we have found an effect which is strikingly similar to this perceptual phenomenon. If a high and a low contrast grating are presented simultaneously, one to each eye, the cell's response to the low contrast stimulus is suppressed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00237480
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  • 17
    Electronic Resource
    Electronic Resource
    Bulbar neurones with axonal projections to the trigeminal motor nucleus in the cat (1986)
    Springer
    Experimental brain research 65 (1986), S. 98-111 
    Details
    ISSN: 1432-1106
    Keywords: Cat ; Interneurones ; Motor control ; Jaw movements ; WGA-HRP ; Retrograde transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The location of bulbar neurones with axons projecting to the ipsi- and contralateral trigeminal motor nucleus were investigated in cats anaesthetized with sodium pentobarbital. Wheat germ agglutinin-conjugated horseradish peroxidase (WGA-HRP) was injected in amounts of 5–24 nl. A volume-calibrated microelectrode was used for recording of evoked potentials and pressure injection of WGA-HRP. The injection site was guided by the position where a maximal antidromic response was evoked by electrical stimulation of the masseteric nerve. The survival time was 19–22 h. In preparations with the depot located in the masseteric subnucleus retrogradely stained neurones were found bilaterally in the borderzone of the trigeminal motor nucleus. Dense populations of stained neurones were observed ipsi- and contralaterally in the dorsal division of the main sensory trigeminal nucleus and the subnucleus-γ of the oral nucleus of the spinal trigeminal tract. Clusters of WGA-HRP-neurones were observed bilaterally in the lateral tegmental field at the level of the subnucleus-β of the oral nucleus of the spinal trigeminal tract, bilaterally dorsal to the facial nucleus and contralaterally adjacent to the hypoglossal nucleus. No stained neurones were found in the gigantocellular reticular nucleus. A group of stained neurones was located in the marginal nucleus of brachium conjunctivum and some were found in the raphé nuclei near obex. Cell profiles were of two types: medium-sized neurones with a triangular profile and 30–40 μm diameter, and fusiform neurones 10×50–70 μm. Convergence of descending cortical and trigeminal afferent inputs on interneurones located in the lateral borderzone of the trigeminal motor nucleus, i.e. the intertrigeminal area, is reported in the preceding paper.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00243833
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  • 18
    Electronic Resource
    Electronic Resource
    Cortically and lingually induced postsynaptic potentials in trigeminal motoneurons after axotomy (1986)
    Springer
    Experimental brain research 61 (1986), S. 272-279 
    Details
    ISSN: 1432-1106
    Keywords: Membrane property ; Postsynaptic potentials ; Axotomized trigeminal motoneuron ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The membrane properties and the efficacy of excitatory and inhibitory synapses were studied in cat masseteric motoneurons (Mass Mns) after axotomy. In axotomized Mass Mns the slope of the primary range in the frequency-current relationship showed a higher gain than that of normal Mass Mns. The safety of antidromic invasion was increased and the initial segment component of antidromic action potentials could not be separated from the somadendritic component. In normal Mass Mns a single shock delivered to the orbital gyrus or the lingual nerve induced long-lasting inhibitory postsynaptic potentials (IPSPs). In two-thirds of Mass Mns explored 30 days after axotomy, a single shock delivered to the orbital gyrus or the lingual nerve evoked a mixture of inhibitory and excitatory synaptic potentials. In Mass Mns 50 days after axotomy, we have demonstrated that the major fraction of the total sample of explored Mass Mns showed long-lasting excitatory postsynaptic potentials followed by IPSPs. The results suggest that in Mass Mns, axotomy is followed by the decline of synaptic efficacy of inhibitory rather than of excitatory synapses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00239517
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  • 19
    Electronic Resource
    Electronic Resource
    Pyramidal tract of the cat: axon size and morphology (1986)
    Springer
    Experimental brain research 61 (1986), S. 303-310 
    Details
    ISSN: 1432-1106
    Keywords: Pyramidal tract axons ; Cat ; Size and morphology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The purpose of this work was to determine the number and morphology of pyramidal tract (PT) axons in the cat, using electron microscopy, modern methods of fixation, and computer-assisted morphometric analysis. Sections taken at the level of the medullary pyramids in three animals were fixed and magnified up to 10,000 x to produce photomicrographs. Morphological data were entered into computer files for analysis by tracing axon perimeters on micrographs mounted on a digitizer tablet. The number of axons per PT averaged 415,000, of which 88% were myelinated and 12% were unmyelinated. 90% of the myelinated axons fell in the diameter range 0.5–4.5 μm. Axons larger than 9 μm diameter accounted for 1% of the total; the largest were 20–23 μm. Myelinated axon mean diameter was 1.98 μm; because of the skewed distribution, with many small axons and a few very large axons, median diameter was 1.60 μm. Size distribution was relatively uniform throughout the PT cross section, with all sizes represented in all regions. However, the more medial regions had a higher proportion of small fibers than the more lateral regions: mean medial diameter was 1.85 μm while mean lateral diameter was 2.09 μm. Myelin sheath thickness averaged 7.9% of fiber diameter for axons up to 11 μm, but was constant at 0.9 μm for larger fibers. Myelinated fibers were distorted from the circular shape in cross section, with a mean circularity index (or form factor) of 0.85, which implies that the fibers could swell about 15% without rupture of the cell membrane. Unmyelinated fibers averaged 0.18 μm diameter (range 0.05–0.6 μm); the largest unmyelinated axons were larger than the smallest myelinated axons. It is concluded that previous work greatly underestimated the number of axons in the cat pyramidal tract.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00239520
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  • 20
    Electronic Resource
    Electronic Resource
    Morphology of vertical canal related second order vestibular neurons in the cat (1986)
    Springer
    Experimental brain research 63 (1986), S. 35-48 
    Details
    ISSN: 1432-1106
    Keywords: Semicircular canals ; Three-neuron arc ; Vestibulo-ocular reflex ; Horseradish peroxidase ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The morphology of vertical canal related second order vestibular neurons in the cat was studied with the intracellular horseradish peroxidase method. Neurons were identified by their monosynaptic potentials following electrical stimulation via bipolar electrodes implanted into individual semicircular canal ampullae. Anterior and posterior canal neurons projected primarily to contralateral or ipsilateral motoneuron pools (excitatory and inhibitory pathways, respectively). The axons of contralaterally projecting neurons crossed the midline at the level of the abducens nucleus and bifurcated into an ascending and a descending main branch which travelled in the medial longitudinal fasciculus (MLF). Two types of anterior canal neurons were observed, one with unilateral and one with bilateral oculomotor projection sites. For both neuron classes, the major termination sites were in the. contralateral superior rectus and inferior oblique subdivisions of the oculomotor nucleus. In neurons which terminated bilaterally, major collaterals recrossed the midline within the oculomotor nucleus to reach the ipsilateral superior rectus motoneuron pool. Other, less extensive, termination sites of both neuron classes were in the contralateral vestibular nuclear complex, the facial nucleus, the medullary and pontine reticular formation, midline areas within and neighboring the raphé nuclei, and the trochlear nucleus. The ascending main axons continued further rostrally to reach the interstitial nucleus of Cajal and areas around the fasciculus retroflexus. The descending branches proceeded further caudal in the medial vestibulo-spinal tract but were not followed to their spinal target areas. In addition to two previously described posterior canal related neuron types (Graf et al. 1983), we found neurons with bilateral oculomotor terminals and a spinal collateral. Typical for posterior canal neurons, the major termination sites were in the trochlear nucleus (superior oblique motoneurons) and in the inferior rectus subdivision of the oculomotor nucleus. Axon collaterals recrossed the midline to reach ipsilateral inferior rectus motoneurons. The axons of ipsilaterally projecting neurons ascended through the reticular formation to join the MLF caudal to the trochlear nucleus. The main target sites of anterior canal related neurons were in the trochlear nucleus and the inferior rectus subdivision of the oculomotor nucleus. Minor collaterals reached the pontine reticular formation and areas in between the fiber bundles of the ipsilateral MLF. In some cases, small collaterals crossed the midline within the oculomotor nucleus to terminate in the inferior rectus subdivision on the contralateral side. The axon proceeded further rostral to project to the interstitial nucleus of Cajal and beyond. The main termination sites of posterior canal neurons were in the superior rectus and inferior oblique subdivisions of the oculomotor nucleus. Minor collaterals were also observed to reach the midline area within the oculomotor nucleus, however, prospective contralateral termination sites could not be identified. More rostral projections were found in the interstitial nucleus of Cajal. The described axonal arborization of second order vestibular neurons reflects the organization of intrinsic coordinate systems as exemplified by the geometry of the semicircular canal and the extraocular muscle planes. These neurons are interpreted to provide a matrix for coordinate system transformation, i.e. from vestibular into oculomotor reference frames, and to play a role in gaze control and related reflexes by distributing their signals to multiple termination sites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00235644
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  • 21
    Electronic Resource
    Electronic Resource
    Electrophysiological evidence for a projection from medial prefrontal and anterior limbic cortex toward the medial preoptic area in the cat (1986)
    Springer
    Experimental brain research 63 (1986), S. 205-215 
    Details
    ISSN: 1432-1106
    Keywords: Prefrontal cortex ; Limbic cortex ; Medial preoptic area ; Axonal branching ; Electrophysiology ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Neurons in cat medial prefrontal cortex, anterior limbic cortex and possibly the indusium griseum were identified by antidromic invasion as having axonal projections towards the medial preoptic region, using both macro- and microstimulation techniques. These projecting axons were found to be of slow conduction velocity (0.2–4.8 m/s) and to in some cases also send branches towards the anteromedial thalamus, mediodorsal thalamus, ventromedial tegmentum, basolateral amygdala or medial forebrain bundle. Threshold-depth curves for axons excited by microstimulation in the medial preoptic region were very steep, with proportionality constants of 0.3–7.1 μm/μA. Calculations based on the threshold-depth curves confirmed that microstimulation was most probably only activating axons within the MPO, and current spread to lateral fibers of passage following macrostimulation in the MPO was not detected in the branching studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00235665
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  • 22
    Electronic Resource
    Electronic Resource
    Differences of visual field representation in the medial and lateral banks of the suprasylvian cortex (PMLS/PLLS) of the cat (1986)
    Springer
    Experimental brain research 64 (1986), S. 77-93 
    Details
    ISSN: 1432-1106
    Keywords: Lateral suprasylvian cortex ; Posterior lateral suprasylvian area ; Topography ; Visual field representation ; Scatter of receptive fields ; Cat ; PMLS ; PLLS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We have studied the orderliness of representation of visual space in the medial and lateral banks of the middle suprasylvian sulcus. Penetrations were made either parallel to the sulcus, in one bank or the other, or vertical, thus crossing the sulcus between the postero-medial (PMLS) and posterolateral (PLLS) divisions of this area. In some cases we found clear evidence for topographical order in the representation of the visual field with a tendency (greater in PMLS than in PLLS) for the receptive fields of cells recorded deeper in the walls of the sulcus to lie closer to the area centralis, but along many penetrations the receptive fields were so large and so scattered that no retinotopic arrangement could be discerned. In PMLS the receptive fields of the majority of units we studied were centred below and close to the horizontal meridian, whereas in PLLS they were distributed over both the upper and lower visual fields with an over-representation of the upper field. Receptive fields were significantly larger in PLLS (mean field area = 442.2 deg2) than in PMLS (mean area = 154.4 deg2); there was also less clear correlation between receptive field size and eccentricity in PLLS (correlation coefficient = +0.25) than in PMLS (corr. coeff. = +0.72). Analysis of the distance between the receptive field centres of consecutively recorded units demonstrated that the mean scatter in both PMLS and PLLS amounts to about half the average receptive field diameter. In summary the topographical representation of visual space is less orderly in PLLS, and may involve a wider area of the visual field. These findings may relate to the segregated visual cortical and extrageniculate thalamic connections that the medial and lateral banks of the LS receive.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00238203
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  • 23
    Electronic Resource
    Electronic Resource
    Evidence of rhythmic inhibitory synaptic influences in hindlimb motoneurons during fictive locomotion in the thalamic cat (1986)
    Springer
    Experimental brain research 64 (1986), S. 217-224 
    Details
    ISSN: 1432-1106
    Keywords: Locomotion ; Cat ; Hindlimb motoneurons ; Inhibition ; Excitation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 1. Intracellular recordings of various motoneurons of proximal hindlimb muscles were performed on thalamic paralyzed cats, during fictive locomotion that was either spontaneous or evoked by stimulation of the subthalamic region. 2. In motoneurons innervating sartorius (medialis and lateralis), vasti (intermedius, medialis and lateralis) and anterior biceps-semimembranous, one depolarization occurred in each locomotor cycle, alternating with a phase of repolarization that was synchronous with the activation of the antagonistic muscle nerve. This latter phase could be decreased or reversed by intracellular injection of chloride ions or current, revealing the presence of inhibitory inputs onto motoneurons. 3. The pattern of membrane potential variations was more complex in motoneurons of rectus femoris and posterior biceps-semitendinosus muscles, but phases of chloride dependent inhibition were nevertheless identified, mainly during the sartorius nerve activation in the case of rectus femoris, and during the vasti and anterior biceps-semimembranosus nerve activations in the case of posterior biceps-semitendinosus. These inhibitory influences were shown to be controlled by the level of activity in exteroceptive afferents. 4. The characteristics of the excitatory and inhibitory inputs to the hindlimb motoneurons identified here are discussed in relation with the organization of the central pattern generator for locomotion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00238216
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  • 24
    Electronic Resource
    Electronic Resource
    The orientation bias of LGN neurons shows topographic relation to area centralis in the cat retina (1986)
    Springer
    Experimental brain research 64 (1986), S. 233-236 
    Details
    ISSN: 1432-1106
    Keywords: Lateral geniculate nucleus ; Orientation bias ; Receptive field ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The orientation sensitivity of LGN cells to flickering square-wave gratings was measured in urethane-anaesthetized paralyzed cats. The mean ratio of the amplitude of peak responses to optimally oriented gratings to that elicited by gratings of the least effective orientation was 3.0 ± 0.3 (S.E.). 58% of the recorded neurons responded best to orientations within 30° of the meridional line joining their receptive field center with the fixation points (area centralis), implying that they were more sensitive to visual contours pointing to the center of the retina.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00238218
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  • 25
    Electronic Resource
    Electronic Resource
    Effect of exogenous dopamine on the hypercapnic ventilatory response in cats during normoxia (1986)
    Springer
    Pflügers Archiv 407 (1986), S. 504-509 
    Details
    ISSN: 1432-2013
    Keywords: Peripheral chemoreceptors ; Central chemoreceptors ; Control of respiration ; Dopamine ; Cat ; Hypercapnia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of exogenous dopamine on the normoxic hypercapnic ventilatory response were assessed in nine chloralose-urethane anesthetized cats using the technique of dynamic end-tidal forcing. The ventilatory responses to step changes in end-tidalP CO 2 (PETCO 2) were measured before (control), during and after intravenous infusion of dopamine (420 μg·kg−1·h−1). Each response was separated into a slow central and a fast peripheral chemoreflex loop by fitting two exponential functions to the measured ventilation. Both loops were described by a CO2 sensitivity, time constant, time delay and a single off-set B (extrapolated PETCO 2, of the steady-state response curve at zero ventilation). Dopamine infusion only caused a significant increase of B (mean 0.3 kPa,P〈0.0001) compared to control; the other model parameters were not significantly affected. After dopamine infusion B returned to significantly lower values (mean 0.2 kPa,P=0.006) than in control. In two additional cats the dopamine administered to the blood which was artificially perfusing the brainstem, did not affect ventilation. We conclude that in normoxic cats the effect of exogenous dopamine on the ventilatory response to CO2 is due to a CO2 independent inhibition of the ventilatory drive which originates outside the brainstem.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00657508
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  • 26
    Electronic Resource
    Electronic Resource
    Chemoreceptor response to hypoxia and hypercapnia in catecholamine depleted rabbit and cat carotid bodies in vitro (1986)
    Springer
    Pflügers Archiv 406 (1986), S. 419-423 
    Details
    ISSN: 1432-2013
    Keywords: Rabbit ; Cat ; Chemoreceptor ; Reserpine ; α-Methyl-p-tyrosine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The response of single chemoafferent fibres to hypoxic and hypercapnic stimulation was studied in vitro under different experimental conditions: 1. control, 2. 24 h after reserpinization (5 mg/kg iv) and 3. 18 h after iv injection of α-methyl-p-tyrosine (100 mg/kg in the rabbit, and 1. control and 2. 24 h after reserpinization (5 mg/kg ip) in the cat. The spontaneous activity was decreased by monoamine depletion. The amplitude of the response to hypoxia and to hypercapnia was decreased by reserpinization in the rabbit and in the cat, the change being less marked in the latter species. Similarly, treatment with·α-methyl-p-tyrosine decreased the ability of chemoreceptors to respond to hypoxia and hypercapnia and, in a few instances, these receptors could only be excited by superfusion of nitrogencquilibrated medium. These results emphasize to possible role of monoamine, and particularly dopamine, in modifying the sensitivity of arterial chemoreceptors to their natural stimuli.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00590946
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  • 27
    Electronic Resource
    Electronic Resource
    Functional characteristics of lumbar visceral afferent fibres from the urinary bladder and the urethra in the cat (1986)
    Springer
    Pflügers Archiv 407 (1986), S. 510-518 
    Details
    ISSN: 1432-2013
    Keywords: Lumbar visceral afferents ; Urinary bladder ; Urethra ; Functional properties ; Visceral nociception ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Neural activity of lumbar visceral afferents supplying the urinary bladder and urethra was analyzed systematically in the cat. The afferent fibres were isolated either from the white rami L3 and L4 in a preparation with closed peritoneal cavity, or from the lumbar splanchnic nerves in a preparation with open peritoneal cavity and investigated for various functional parameters. Seventy five single units and 9 multiunit bundles were analyzed. 1) About 50% of the afferent units had some ongoing activity (0.2 to 1 imp/s). Two thirds of the afferent axons were thin myelinated (conduction velocity 3–15 m/s), the rest were presumably unmyelinated (conduction velocity below 2 m/s). 2) The receptive fields of the afferent units consisted —with one exception — of single mechanosensitive sites on the surface of the bladder and urethra. Most receptive fields were situated on the dorsal side of the bladder. 3) Afferents with receptive fields on or in the bladder wall responded in a graded manner to passive distension and isovolumetric contraction at intravesical pressures ranging from about 10 to 70 mm Hg. The thresholds for exciting the afferent units ranged from less than 10 mm Hg to about 30 mm Hg intravesical pressure, most of them being less than 20 mm Hg. Generally, the discharge rate of the afferent units gave a reliable representation of the intravesical pressure to the lumbar spinal cord. 4) Urethral units exhibited either no responses to the graded distensions and contractions of the urinary bladder, or responded with low discharge rates at higher intravesical pressures. 5) The results do not support the notion that noxious events in the urinary bladder are encoded by “specific” nociceptive visceral afferents to the lumbar spinal cord but possibly by some other mechanism of encoding.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00657509
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  • 28
    Electronic Resource
    Electronic Resource
    Distributional pattern of serotonin-immunoreactive nerve fibers in the lateral geniculate nucleus of the rat, cat and monkey (Macaca fuscata) (1986)
    Springer
    Cell & tissue research 243 (1986), S. 249-253 
    Details
    ISSN: 1432-0878
    Keywords: Serotonin-immunoreactive nerve fibers ; Lateral geniculate nucleus ; Immunohistochemistry ; Rat ; Cat ; Monkey (Macaca fuscata)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The distribution of serotonin-containing nerve fibers in the lateral geniculate nucleus (LGN) of the rat, cat, and monkey (Macaca fuscata) was studied by use of the peroxidase-antiperoxidase method and an antiserum against serotonin. In all three species, the pattern of fibers was denser in the ventral portion of the LGN (LGNv) than in the dorsal nuclear portion (LGNd). In the LGNd of rat, serotonin-immunoreactive fibers were evenly distributed in the form of a dense network, but in cat and monkey there were marked regional differences. Serotonin-immunoreactive elements were most numerous in the C complex and medial interlaminal nucleus of cat, and in the S layer and interlaminar zones of Macaca fuscata.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00251038
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  • 29
    Electronic Resource
    Electronic Resource
    Observations on the primary sensory ending of tenuissimus muscle spindles in the cat (1986)
    Springer
    Cell & tissue research 246 (1986), S. 309-319 
    Details
    ISSN: 1432-0878
    Keywords: Muscle spindle ; Sensory innervation ; Mechanosensory transduction ; Morphogenesis ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The arrangement of preterminal and terminal axon branches in the primary sensory endings of cat tenuissimus muscle spindles was studied using whole-mount and serial-section techniques. Although in every case one firstorder preterminal branch was supplied exclusively to the bag1 type of intrafusal muscle fibre, the preterminal branching patterns differed considerably in detail. Terminals varied widely in size and location. Their precise form varied according to their position on the intrafusal muscle fibres rather than their relationship to preterminal branches. Terminals derived from separate preterminal branches remained separate and did not fuse with themselves or each other. Individually bag1 fibres had most terminals, chain fibres least. The surface of the muscle fibres were differentially indented by the terminals, least in bag1 fibres and most in chain fibres. The results are discussed in relation to mechanosensory transduction and to the factors involved in determining the form of the primary ending.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00215893
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  • 30
    Electronic Resource
    Electronic Resource
    Autoradiographic localization of transported neutral amino acids in epithelia of cat submandibular and sublingual salivary glands (1986)
    Springer
    Cell & tissue research 246 (1986), S. 353-358 
    Details
    ISSN: 1432-0878
    Keywords: Amino acid uptake ; Autoradiography ; Salivary gland ; Serine ; Phenylalanine ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Light-microscopic autoradiography was used to localize the cellular sites for neutral amino acid uptake in submandibular and sublingual salivary gland epithelia. The vasculature of isolated glands was perfused for 3–5 min with either L-(3-3H)serine or L-(4-3H)phenylalanine and then fixed by perfusion with buffered glutaraldehyde. In the submandibular gland the small neutral amino acid L-serine and the aromatic amino acid L-phenylalanine were localized to central acinar cells, demilunar cells and ductal cells. In the sublingual gland silver grains associated with each of these tritiated amino acids were localized to central acinar and ductal cells. Perfusion of both submandibular and sublingual glands with unlabelled L-serine (25 mM) or L-phenylalanine (30 mM) resulted in a significant decrease in the silver grain density associated with each labelled amino acid. The absence of silver grains in the lumina of acinar and ductal cells and the presence of tight junctions near the apical surface of the epithelium strongly suggest that the initial uptake of these amino acids was mediated by basolateral plasma membrane carriers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00215897
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  • 31
    Electronic Resource
    Electronic Resource
    The transverse tubular system of cat intrafusal muscle fibres (1986)
    Springer
    Cell & tissue research 244 (1986), S. 197-202 
    Details
    ISSN: 1432-0878
    Keywords: Transverse tubular system ; Sarcoplasmic reticulum ; Triads ; Intrafusal muscle fibre ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary A modified staining technique for transverse tubular and sarcoplasmic reticular systems was used to investigate their occurrence in different types of intrafusal muscle fibres in cat tail spindles. Intrafusal muscle fibres can be divided into three basic regions, namely, the periaxial space (A-region), intracapsular area (B-region) and the extracapsular area (C-region); the components of these systems were seen to vary in structure and distribution. The occurrence of these systems also varied among the different types of intrafusal muscle fibres, namely, the bag1, bag2 and chain fibres. In bag1 fibres components were sparse in the A-region, increased slightly in the B-region, but were most developed in the C-region; triads were consistently located at the border between A- and I-bands. In bag2 fibres membrane components were noted in the A-region but were more abundant in the B-region where some tubular components showed transverse and longitudinal branches linked together in the form of a network; membrane systems diminished towards the C-region. The majority of triads were located within the A-bands. In chain fibres the membrane systems occurred more commonly in the A-region, while in the B- and C-regions, the transverse tubular system possessed numerous transverse and longitudinal branches forming irregularly distributed tubular networks. Some tubular branches were dilated, while other branches terminated as sacs among arrays of the sarcoplasmic reticular system in I-bands. Some transverse tubules bifurcated into two branches with numbers of dilated sarcoplasmic reticular cisternae lying on either side, or between, the branches. Triads sometimes occurred between A- and I-bands, but, generally, were situated well within A-bands.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00218399
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  • 32
    Electronic Resource
    Electronic Resource
    Exercise induced increases in muscle fiber number (1986)
    Springer
    European journal of applied physiology 55 (1986), S. 137-141 
    Details
    ISSN: 1439-6327
    Keywords: Weight-lifting exercise ; Cat ; Flexor carpi radialis muscle ; Nitric acid digestion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effect of weight-lifting, which induced muscular enlargement, on fiber number was tested in the flexor carpi radialis muscle by operantly conditioning 6 cats to flex their right wrist against increasing resistance for an average of 101 weeks. The left was used as a control. At the end of training, the cats were performing “one-arm“ lifts with an average of 57% of their body weight. There was an 11% greater muscle weight (P〈0.01) and 9% (P〈0.02) more fibers in the exercised muscles from the right limb than in the left. This study using a different method, supports our earlier observations that prolonged weight-lifting exercise significantly increases the total number of muscle fibers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00714995
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  • 33
    Electronic Resource
    Electronic Resource
    α-Helical oligopeptides with hydrophobic side chains soluble in lipophilic solvents (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1-4 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360250102
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  • 34
    Electronic Resource
    Electronic Resource
    Conformations of dinucleoside monophosphates in relation to duplex DNA structures (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 17-30 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mononucleotide conformations are important in understanding the structural aspects of nucleic acids and polynucleotides. In order to study the influence of stacking interactions between adjacent bases in a polynucleotide on the preferred conformations of mononucleotides, conformational energy calculations have been carried out on dinucleoside monophosphate fragments. Four base sequences - d(ApT), d(TpA), d(CpG), and d(GpC) -  have been analyzed in the framework of helical structures. Flexibility of the furanose ring has been incorporated in the investigations. Energetically favored conformers of the four compounds correspond to a variety of left- and right-handed uniform helical structures, similar to those of the commonly observed polymorphous forms. Implications of these investigations on the further understanding of double-helical polynucleotide conformations are briefly discussed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360250104
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  • 35
    Electronic Resource
    Electronic Resource
    Vibrational circular dichroism of polypeptides, V. A study of 310-helical-octapeptides (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 79-89 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have measured vibrational CD spectra in the 3600-1250 cm-1 region of two monodisperse, protected octapeptides, which form right-handed 310-helices in CDC13 solution. The spectra are similar in sign pattern to those obtained for right-handed α-helices in solution but are smaller in magnitude and, additionally, provide evidence of some line-shape differences. The delineation of this type of ordered conformation was accomplished by means of 1H-nmr. Such a solution structure is consistent with the x-ray crystal structure of one of these molecules.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360250107
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  • 36
    Electronic Resource
    Electronic Resource
    Interaction of calcium ions with gastrin fragments of increasing chain length (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 135-152 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The interaction of a series of biologically active gastrin fragments with calcium ions has been investigated by CD in trifluoroethanol. It was found that the gastrin octapeptide pGlu10,Nle15-HG[10-17] binds one calcium ion per molecule. The hypothesis is made that the binding involves the C-terminal, biologically important tetrapeptide. When the chain is elongated to the gastrin nonamer pGlu9,Nle15-HG[9-17], a second binding site is available, which is most likely situated at the N-terminal part of the molecule. Further elongation of the peptide chain up to the dodecapeptide pGlu6,Nle15-HG[6-17] does not provide any additional binding site. Saturation of the two sites in the shorter peptides produces different changes in the chiroptical properties in the near- and far-uv. As the chain is elongated, this difference tends to disappear. This result is consistent with an increased conformational order of the longer peptides. In the shorter fragments, the strength of this second binding is appreciably lower than that of the first, while in the longer peptides, the strength of the two bindings is comparable. On the assumption that the variation of the CD properties is proportional to the extent of binding, the constant for the binding of the second ion was determined to be of the order of 5 × 105 L/mol for the nonapeptide.
    Additional Material: 10 Ill.
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    Masthead (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986) 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360250201
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  • 38
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    UV-induced reduction of Cu(II) in DNA complex studied by Cu-K-edge XANES (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 217-221 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360250202
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  • 39
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    Conformational properties of gastrin peptides: Synthesis, biological activity, and preliminary CD characterization of the (Asp)5 analog of des-Trp1, Leu12-minigastrin (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 229-234 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360250204
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  • 40
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    A molecular mechanical study of netropsin-DNA interactions (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 249-266 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We present molecular mechanical calculations on the complexes of netropsin with dA6·dT6, d(TATATA)2, d(CGCGCG)2, and d(CGCGAATTCGCG)2. The complexes were model built using computer graphics and then completely energy refined. Our calculations are consistent with the observed AT preference for netropsin and suggest that mixed sugar pucker geometries should be more stable than uniform in netropsin complexes with poly[d(A-T)]·poly[d(A-T)] and poly(dA)·poly(dt). The netropsin·d(TATATA) and netropsin·dA6·dT6 complexes are significantly different in structure, leading to a possible reason why the observed thermodynamics of netropsin-association with poly[d(A-T)]·poly[d(A-T)] and with poly(dA)·poly(dT) are so different. We also model built and energy refined a structure of netropsin-d(CGCGAATTCGCG)2 using as a guide the nmr data of Patel [(1982) Proc. Natl. Acad. Sci. USA, 79, 6424-6428] and found a three-dimensional structure qualitatively consistent with the NOE enhancements observed by him. After our calculations were completed, we learned of an x-ray structure of a netropsin:d(CGCGAATTCGCG)2 complex, and we compared the structure found in our calculation with the x-ray structure.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360250207
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  • 41
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    Dependence of oxygen quenching of intercalated methylene blue triplet lifetime on DNA base-pair composition (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 307-316 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We utilize the dynamic quenching of the triplet state of methylene blue by molecular oxygen to observe changes in the rate at which oxygen can penetrate the helix as a function of base-pair composition. The results indicate that the interior of the oligonucleotide dA-dT is more accessible than dG-dC to small molecules such as dioxygen.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360250211
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  • 42
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    Electronic Resource
    Masthead (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986) 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360250301
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  • 43
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    Spermine-nucleic acid interactions: A theoretical study (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 375-392 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The interaction of spermine with nucleic acids is simulated theoretically using refined semi-empirical energy formulae and an advanced minimization procedure. Various nucleic acids are considered: model homopolymeric DNA's, a dodecamer (CGCGAATTCGCG) of type B-DNA, as well as a transfer RNA, tRNAPhe. The dominant role of electrostatic potential in determining the preferential binding sites of spermine is demonstrated in each of these cases and the role of counterions, nucleic acid structure, and base-pair sequence is analyzed.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360250302
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  • 44
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    Temperature dependence of dielectric constant at 10 GHz of Na-DNA gels (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 241-247 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Permittivity ε′ and dielectric loss ε″ of aqueous Na-DNA gels have been measured at 10 GHz in the temperature interval -15 to + 45°C. The experimental results are analyzed in terms of a three-component equation (Na-DNA, interfacial water, bulk water) and yield a value of 35 water molecules/nucleotide interacting with DNA. According to theoretical and experimental data the presence of strongly bonded and weakly bonded water is considered. The modified water exhibits a mean dielectric relaxation time two-or threefold greater than that of bulk water.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360250206
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  • 45
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    The effect of solvent viscosity and temperature on DNA viscoelastic behavior (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 291-306 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effect of solvent viscosity (ηs) and temperature (T) on the shape of the concentration dependence of the principal and total recoils in creep-recovery viscoelastometry experiments has been studied for T4 DNA solutions. The range of DNA concentration (c) was 2 - 40 μg/ml; glycerol, 70-80% v/v, sucrose, 60% v/v; NaCl, 5 mM - 1M; and T, 275 - 323 K. A linear proportionality between recoil and c was obtained at high ηs/T. At low ηs/T, the c-dependence was nonlinear, approaching saturation at higher c. At low c, the slope of both curves was the same. Transition between “linear” and “nonlinear” values occurred over a narrow range of ηs/T (a width of 1-5 K if ηs/T was changed by varying T). (ηs/T)tr, the midpoint of the transition, was independent of solvent properties other than viscosity. Also, (ηs/T)tr increased with c. For a given c, ηs/T values above this transitional value yield linear behavior; below this, nonlinear behavior. The ratio of linear to nonlinear recoil values is a linear function of c with Kc, the slope of this dependence, independent of ηs and T. A kinetic model for the observed nonlinearity of recoil with c is presented. It explains the independence of Kc on ηs and T. An attempt has been made to explain the linear-nonlinear transitions by comparison of τ1 and TR, the lifetime of the contact points of the polymer network in the de Gennes theory. The nonlinear values are consistent with a pseudogel that exists when τ1 〈 TR. At τ1 〉 TR, the DNA behavior is similar to that in dilute solutions (linear values). Thus, the condition for transition is τ1 = TR. However, some unsolved problems remain.
    Additional Material: 9 Ill.
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  • 46
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    The growth of large single crystals of lysozyme (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 337-350 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: If protein single crystals larger than those suitable for x-ray analysis are obtained, various spectroscopic, thermal, mechanical, and electrical measurements become possible. To understand the factors governing the crystal size, tetragonal lysozyme crystals were grown in batches at 15°C from solutions of different protein and salt concentrations between pH 4-7. The number and size of the crystals, and the protein concentration remaining in the supernatant, varied markedly with the initial salt amount, pH, and cation species, but large crystals always grew when the initial protein concentration (P) was in a narrow range of 2.5-3 times the crystal solubility (S). It was also shown (1) that the period before the first crystals appeared (D) varied as D ∝ (P/S)-n, where n ≃ 5, and (2) that many previous experiments used more supersaturated solutions than the optimal ones thus determined. The reason why large crystals grow only from moderately supersaturated solutions is discussed. The crystal size of the orthorhombic form grown at 40°C was less sensitive to pH and P than the tetragonal form. An effort to measure D and the solubility at 40°C revealed many differences between the two crystal forms, which we ascribe to different interactions to promote crystallization.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360250213
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  • 47
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    Conformational changes of pinellin in solution using intrinsic fluorescence and CD as probes (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 393-405 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Pinellin is a plant protein extracted from the rhizome of the Chinese herb Pinellia. It has the ability to abort early pregnancy in mice as well as in rabbits. Studies on the conformational changes of pinellin have been carried out in our laboratory using intrinsic fluorescence and CD. Experimental results show that some tryptophanyl side chains are buried more deeply than others, which results in the heterogeneity of tryptophanyl emission. CD data indicated a high content of β-pleated sheet and β-turn for the backbone conformation. The results of fluorescence and CD measurements both demonstrated the presence of intermediates along the path of denaturation. The following was proposed as the unfolding mechanism of pinellin in 6M guanidine hydrochloride: native state → first intermediate → second intermediate → fully unfolded state.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360250303
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  • 48
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    Examination of the secondary structure of proteins by deconvolved FTIR spectra (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 469-487 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Fourier transform ir (FTIR) spectra of 21 globular proteins have been obtained at 2 cm-1 resolution from 1600 to 1700 cm-1 in deuterium oxide solution. Fourier self-deconvolution was applied to all spectra, revealing that the amide I band of each protein except casein consists of six to nine components. The components are observed at 11 well-defined frequencies, although all proteins do not exhibit components at every characteristic frequency. The root mean square (RMS) deviation of 124 individual values from the 11 average characteristic frequencies is 1.9 cm-1. The observed components are assigned to helical segments, extended beta-segments, unordered segments, and turns. Segments with similar structures do not necessarily exhibit band components with identical frequencies. For instance, the lower frequency beta-structure band can vary within a range of approximately 15 cm-1. The relative areas of the individual components of the deconvolved spectra were determined by a Gauss-Newton, iterative curve-fitting procedure that assumed Gaussian band envelopes for the deconvolved components. The measured areas were used to estimate the percentage of helix and beta-structure for each of 21 globular proteins. The results are in good general agreement with values derived from x-ray data by Levitt and Greer. The RMS deviation between 22 values (alpha- and beta-content of 11 beta-rich proteins measured by both techniques) is 2.5 percentage points; the maximum absolute deviation is 4 percentage points.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360250307
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  • 49
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    Fluorescence decay of ethidium bromide in the presence of the Z-conformation of poly-(dG-dC) and of poly(dG-dC) modified by chlorodiethylenetriamine platinum(II) chloride (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 507-518 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A time-resolved fluorescence study of ethidium bromide (EB) in the presence of poly(dG-dC) and of poly(dG-dC) modified by chlorodiethylenetriamine platinum(II) chloride is presented under solvent conditions in which these polymers adopt the Z-conformation (high ionic strength). It is shown that these polynucleotides can intercalate a very small quantity of EB. The binding parameters have been determined. The fluorescence lifetime of EB is slightly higher when bound to the Z-conformation (≃25 ns) than when bound to the B-conformation (≃23.7 ns). The nature of the salt has been checked. In the presence of 2.5M NaClO4, no transition from the Z-conformation to another conformation is observed when EB is added. On the contrary, in the presence of 4.25M NaCl, EB induces a cooperative transition from the Z-conformation to a conformation characterized by a much higher affinity for EB intercalation. In the case of poly(dG-dC) this last conformation is identical to the one observed at low ionic strength (B-conformation), but in the case of the platinated polymer this conformation is slightly different, as judged by the smaller value of the fluorescence lifetime of the intercalated EB.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360250309
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  • 50
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    DNA orientation during gel electrophoresis and its relation to electrophoretic mobility (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 539-554 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Intensities of polarized fluorescence from ethidium bound to phage λ DNA undergoing agarose gel electrophoresis were measured. The intensities were strongly field dependent at voltage gradients of 8 V/cm, consistent with a partial orientation of DNA helices in the direction of electrophoresis about 500 times larger than seen in the same field in solution. Such an orientation was predicted by a reptation model of gel electrophoresis advanced by Lumpkin et al. [(1985) Biopolymers, 24, 1573-1593]. The present results can be fit successfully to this theory with a single adjustable parameter, the gel-DNA contact distance. Also, λ DNA electrophoretic mobilities in the same concentration gel were determined using the same buffer system. Both orientation and mobility measurements can be fit to the reptation theory within a factor of two using the same values of two parameters, the gel-DNA contact distance and the ratio of DNA charge to frictional coefficient.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360250403
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  • 51
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    Effect of NaCl on the association of thrombin with heparin (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 527-537 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The association of heparin with thrombin was investigated by fluorometric titration. A maximum of 25% of the fluorescence of fluorescein-labeled heparin (FTC-heparin) was quenched at thrombin saturation in the absence of NaCl. FTC-heparin (H) associated tightly with thrombin (T) and the association constant of the ternary complex, H2T, formed in the absence of NaCl, was calculated to be 1.7 × 108M-1. However, the association was strongly influenced by the NaCl concentration, and the association constant of the equimolar complex, HT, formed in 0.15M NaCl was found to be 1 × 106M-1. The first-order rate constant, kapp, for inactivation of thrombin by antithrombin III (AT III) and low-affinity heparin (LA-heparin) was comparable with that of high-affinity heparin (HA-heparin) in the absence of NaCl, but decreased with an increase in the concentration of NaCl. The decreased enhancement of the thrombin-AT III reaction by LA-heparin at high NaCl concentration appeared to result from a decreased association of thrombin with LA-heparin, thus reducing the formation of the ternary complex, thrombin-LA-heparin-AT III.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360250402
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  • 52
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    Structural studies of poly(α-aminoisobutyric acid) (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 607-625 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electron-diffraction pattern of an oriented film of poly(α-aminoisobutyric acid) in the 310-helical conformation has been analyzed. The conformation was obtained by a linked-atom least-squares refinement of average values from crystal structures. Specimens treated with dichloracetic acid, to improve their crystallinity, conform to space group R3c with a = 21.8 Å, c = 5.95 Å. The structure contains channels that can accommodate molecules of dichloracetic acid. One molecule of acid per six residues fills the channels, and the R-factor then is 34% using 23 reflections. Ir evidence is presented to show that the acid may hydrogen bond to the peptide groups. Some reflections occasionally observed on the diffraction photographs are attributed to a 15/4 α-helix. The significance of the results is considered in relation to Aib-containing peptides.
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    URL: http://dx.doi.org/10.1002/bip.360250407
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    The relationship of bound water to the IR amide I bandwidth of albumin (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 639-654 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Four different types of ir experiments, involving changes in pH, changes in pressure, and the use of nonaqueous solvents, and with either albumin molecules dissolved in saline or adsorbed albumin films, support the hypothesis that the bandwidth of the amide I vibration of albumin is directly related to the amount of bound water in this protein. From the amide I band narrowing and the amide I shift to higher frequencies, it is proposed that a more ordered helix structure results as the amount of bound water is decreased.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360250409
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  • 54
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    Sequence-dependent recognition of DNA duplexes: Netropsin complexation to the TATA site of the d(G-G-T-A-T-A-C-C) duplex in aqueous solution (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 707-727 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have recorded one-dimensional exchangeable proton and two-dimensional nonexchangeable proton nmr spectra on the complex of netropsin with the self-complementary d(G-G-T-A-T-A-C-C) duplex in aqueous solution between 25° and 35°C. The antibiotic amide, pyrrole, and methylene protons, and the nucleic acid base and sugar H1′, H2′, H2″, and H3′ protons, have been assigned from an analysis of the two-dimensional nuclear Overhauser effect (NOESY) spectra of the complex. We observe intermolecular NOEs between the antibiotic concave face amide, pyrrole, and CH2 resonances, and the adenosine H2 and sugar H1′ protons of base-pairs T3·A6 and A4·T5 in the central TATA core of the d(G1-G2-T3-A4-T5-A6-C7-C8) duplex. We present a molecular model outlining these seven antibiotic-DNA contacts for the complex in solution. The observed line-broadening of several base and sugar protons at the TATA minor groove netropsin binding site in the complex at 35°C are interpreted in terms of intermediate exchange between two orientations of bound netropsin on the duplex.
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    URL: http://dx.doi.org/10.1002/bip.360250413
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  • 55
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    Influence of different tripeptides on the stability of the collagen triple helix. I. Analysis of the collagen sequence and identification of typical tripeptides (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1069-1080 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The amino acid sequence of the collagen α1(I) chain (calf) is analyzed. Deviations of random tripeptide distribution leads to the definition of clusters. Inside these regions, collagen-typical tripeptides are located. Besides Gly-Pro-Hyp, Gly-Pro-Ala, and Gly-Ala-Hyp, the polar sequences Gly-Glu-Hyp, Gly-Ala-Arg, Gly-Glu-Arg, and Gly-Pro-Lys form typical sequences. The neighborhood of each tripeptide is analyzed and classified. The proximity to the collagen-typical tripeptides is registered. Cluster theory: Less-typical sequences also fold as members of the collagen triple helix and they are as reasonable as well as important for the collagen structure as the cluster tripeptides, but only the latter are important for the nucleation of the triple-helical folding.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360250607
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  • 56
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    Peptide-bond distortions and the curvature of α-helices (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1087-1093 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Solvent accessible peptide bonds in proteins exhibit a 1-3° compression of the OCN bond angle and a corresponding expansion of the NCCa bond angle, relative to buried peptide bonds. These changes are consistent with an increase in hydrogen bonding to the carbonyl oxygen accompanying solvent exposure (J. D. Dunitz and F. K. Winkler, (1975) Acta Cryst. B31, 251-263). For amphiphilic structures such as α-helices, systematic differences in peptide-bond geometry between solvent-exposed and buried residues will generate significant curvature. A decrease of 4° in the OCN bond angle between hydrophilic and hydrophobic sides of an amphiphilic helix will lead to smooth bending, with a radius of curvature of about 70 Å. This curvature is in the range observed for α-helices in proteins. Helix curvature is estimated to have only a small effect on the magnitude and direction of the helical dipole moment.
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    URL: http://dx.doi.org/10.1002/bip.360250609
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  • 57
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    SANS studies of concentrated protein solutions. I. Bovine serum albumin (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1157-1175 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Small-angle neutron scattering (SANS) was used to examine concentrated bovine serum albumin solutions of up to 20% protein w/v. At higher protein concentrations, scattering data show distinct features that can be ascribed to strong intermolecular interactions. Differential scattering cross-sections are fitted to a theoretical model of interparticle potential consisting of a hard core plus an exponentially decaying “tail.” For moderate ionic strength (0.03M K Acetate, pH 5.9), the intermolecular interaction agrees with the double-layer repulsive part of the well-known DLVO (Derjaguin, Landau, Verwey, Overbeek) theory for interacting colloidal particles. We thus demonstrate that it is possible to determine size parameters and the surface charge of protein molecules in dense solutions. At high salt concentrations (≥0.2M NaCl) data can be fitted by the same potential model, although interpretation in terms of DLVO theory is not possible. Even in this case, however, “effective” molecular size and potential parameters can be determined.
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    Diffusion of DNA in a gel under an intermittent electric field (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1179-1184 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360250702
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    Shape complementarity at the hemoglobin α1β1 subunit interface (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1229-1247 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A computational method for attempting to predict protein complexes from the coordinates of the individual proteins has been developed. It is based on matching complementary patterns of knobs and holes. The computer algorithm correctly and uniquely predicts the association of the alpha and beta subunits to form the αβ dimer corresponding to the α1β1 interface in the hemoglobin tetramer. It fails to correctly dock trypsin inhibitor onto trypsin. Nevertheless, this lone success is still a significant advance over previous protein-docking algorithms. The method is also important because it introduces several ways to measure the shape of protein surface regions.
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    Enantioselective interactions of inversion-labile trigonal iron(II) complexes upon binding to DNA (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1209-1228 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We studied the interactions of the substitution-inert inversion-labile complexes Fe(bipy)32+ and Fe(phen)32+ [and the inversion-stable complex Ru(bipy)32+] with DNA. The association of these complexes to DNA is mainly electrostatic, and Fe(phen)32+ shows a more effective binding to DNA than the two bipyridyl complexes, possibly owing to a different binding mode. The interactions are enantioselective, leading to a Pfeiffer shift in the diastereomeric inversion equilibria and an excess of the Δ-enantiomer of Fe(phen)32+ and Fe(bipy)32+, which is directly monitorable through CD. The partition constants for the inversion equilibrium range from 1.3 to 2.0 for Fe(bipy)32+ and Fe(phen)32+, depending on ionic conditions. From flow LD information about the orientation of the complexes on DNA was obtained: it is consistent with a fit of the Δ-enantiomer in the major groove of the right-handed DNA helix. The mechanisms of interaction are discussed against equilibrium, spectroscopic, and kinetic data.
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    Distribution of Mn2+ ions around poly(rI)·poly(rC) (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1283-1297 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The distribution of bound Mn2+ ions about poly(rI)·poly(rC) has been studied by measuring the effect of this paramagnetic metal ion on the relaxation behavior of poly(rI)·poly(rC) protons. By combining selective spin - lattice and spin - spin relaxation rates for various protons, some of the principle regions of ion association can be identified. The relaxation data on the CH6 proton are consistent with a 〈 10% occupancy of phosphate inner-sphere binding sites. The broadening of the imino proton resonance requires a substantial occupancy of sites located in the major groove, possibly near IN7. This would also be consistent with the observation that IH8 resonance is the proton most susceptible to relaxation by Mn2+. The relaxation data for the IH2 proton indicate a relatively low occupancy of minor-groove binding sites (e.g., IN3).
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    Adsorption of thionine on heparin studied by combining ultrafiltration and difference VIS spectroscopyThis paper is dedicated to Prof. Georg Manecke on the occasion of his 70th birthday. (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1273-1281 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The combination of ultrafiltration and difference spectroscopy allows the quantitative determination of spectra of thionine bound to heparin. The spectra of the bound dye do not depend on the degree of coverage; this and the shape of the Scatchard plot show that “all-or-none” binding is valid. A calculus of variations based on a modification of the Hill plot shows that aggregates of seven thionine cations are bound. Tetrasaccharides with an average charge of two carboxylate and five sulfate groups are suggested to be the binding sites. The binding constant given for one mole thionine is 4.4 · 105 M-1. The Gibbs enthalpy for binding of one mole of thionine is -31.7 kJ·M-1 at 20°C.
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    URL: http://dx.doi.org/10.1002/bip.360250708
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    Kinetics of ethidium's intercalation in packaged bacteriophage T7 DNA: Effects of DNA packing density (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1345-1357 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of ethidium's intercalative binding to DNA packaged in bacteriophage T7 and two T7 deletion mutants have been determined, using enhancement of fluorescence to quantitate binding. At a constant ethidium concentration, the results can be described as first-order binding with two different rate constants, k1* (= k1 + k-1) and k2* (= k2 + k-2). The larger rate constant (k1*) was at least four orders of magnitude smaller than the comparable first-order forward rate constant for binding to DNA released from its capsid. At 25°C values of k1* decreased as the amount of DNA packaged per internal volume increased. This latter observation indicates that the rate of ethidium's binding to packaged T7 DNA is limited by an event that occurs inside of the DNA-containing region of T7, not by the crossing of T7 capsid's outer shell. Arrhenius plots of kM1* are biphasic, indicating a transition for packaged DNA at a temperature of 20°C. The data indicate that k1* s are limited by either sieving of ethidium during its passage through the packaged DNA or subsequent hindered intercalation.
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    Masthead (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986) 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/bip.360250801
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    Molecular structure of the cis-syn photodimer of d(TpT) (cyanoethyl ester) (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1399-1417 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The three-dimensional structure was determined by x-ray crystallography for d(T[p](CE)T), a uv photoproduct of the cyanoethyl (CE) derivative of d(TpT), having the cis-syn cyclobutane (CB) geometry and the S-configuration at the chiral phosphorus atom. The crystals of C23H30N5O12P · 2H2O belong to the orthorhombic space group P212121 (Z = 4), with cell dimensions a = 11.596 Å, b = 14.834 Å, and c = 15.946 Å, containing two water molecules per asymmetric unit. The CB ring is puckered with a dihedral angle of 151°. The two pyrimidine bases are rotated by -29° from the position of direct overlap of their corresponding atoms. This represents a major distortion of DNA, since in DNA adjacent thymines are rotated by +36°. The pyrimidine rings are puckered with Cremer-Pople parameters for T[p] and in parentheses [p]T: Q: 0.24 Å (0.31 Å); θ: 123° (120°); φ: 141° (86°). These represent half-chairs designated as 6H1 (T[p]) and 6H5 ([p]T). The CB and pyrimidine ring conformations are interrelated, and we postulate that they execute a coupled interconversion in solution. The T[p] segment has the syn glycosyl conformation, a 2T3 sugar pucker, and gauche- conformation at C4′-C5′; the [p]T segment is anti, 3T4, trans. The C5′-O5′ torsion of the [p]T unit is -124.5°, and the C3′-O3′ torsion of the T[p] unit is -152.9°. Bond angles and bond lengths involving the phosphorus atom are similar to those of other phosphotriesters. The P-O3′ and P-05′ torsion angles are -138.1° and 58.6°, respectively. Several intermolecular (but no intramolecular) hydrogen bonds are found in the crystal.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360250804
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    Conformation of mucous glycoproteins in aqueous solvents (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1505-1517 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Light-scattering techniques have been used to measure the z-average radius of gyration Rg z-average translational diffusion coefficient Dt and weight-average molecular weight Mw of porcine submaxillary mucin (PSM) in solution. PSM isolated at low shear in the presence of protease inhibitors has a Mw about twice as large as a sample prepared without these precautions. The former sample has a Mw of 17 × 106 in 0.1M NaCl, which decreases to 8 × 106 in 6M guanidine hydrochloride (GdnHCl) and then to 2 × 106 on addition of 0.1M mercaptoethanol to the 6M GdnHCl solution. The Rg or D-1t values obtained for PSM in this work superimpose with those of other authors for different mucin glycoproteins, leading to linear log-log relationships to the molecular weight of the protein core. Comparison of these results with those in the literature for denatured proteins suggest that mucins are linear random coils in which the protein core is stiffened by the presence of the oligosaccharide side chains. The length of the oligosaccharides and the nature of the solvent have little effect on the extension of the protein core. This suggests that the stiffness of the protein core is maintained by steric repulsion of the residues at the beginning of the oligosaccharide chains.
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    Conformation and aggregation of melittin: Effect of pH and concentration of sodium dodecyl sulfate (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1493-1504 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformation of melittin, a surface-active polypeptide, in solution was studied by CD spectra between 190 and 240 nm. The molecule was essentially unordered (possibly with a trace of helix) in water without salt at neutral pH. Upon deprotonation of four of the six cationic groups at pH 12 the polypeptide became partially helical (about 35%). The addition of NaDodSO4 to an aqueous melittin solution first caused the solution to become turbid but it became clear again in excess surfactant solution. The conformational changes depended on the molar NaDodSO4/melittin ratio, R. With R from 2.34 to 23.4, the melittin solution was turbid and the polypeptide conformation was probably a mixture of α-helix and β-sheets. This was supported by the ir spectrum of the turbid solution, which indicated the presence of both conformations. With R = 46.8 or 468 (1 or 10 mM NaDodSO4) the polypeptide conformation was characteristic of an α-helix, about 70-80% of the molecule, regardless of whether the surfactant was above or below its critical micelle concentration. This compared well with the x-ray results of 92% helix in crystals. The lower helicity of melittin in NaDodSO4 solution might be attributed to the end effects that destabilize the first and last turn of an helix at its N- and C-terminus, respectively.
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    URL: http://dx.doi.org/10.1002/bip.360250808
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    Evolutionary similarity among peptide segments is a basis for prediction of protein folding (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1565-1577 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Short segments of polypeptide, from a protein for which the primary sequence but not the three-dimensional structure is known, are compared to a library of known structures. The basis of comparison is the probability with which residues in the unknown segment might substitute through evolution for residues in segments of known structure. In test cases, segments from known structures that are similar in sequence to those from a protein treated as unknown are often found to be similar in three-dimensional structure to one another and to the true structure of the “unknown” segment. This provides a basis for prediction of the local configuration (secondary structure) of polypeptides.
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    Can the double helix be parallel? (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1603-1606 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360250903
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    The crystal structure of the photosynthetic inhibitors DCMU and DTPU (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1615-1621 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: X-ray diffraction studies have been carried out on a single crystal of the photosynthetic inhibitors N-(3,4-dichlorophenyl)-N′-dimethylurea (DCMU) and its newly synthesized spin-labeled analog N-(3,4-dichlorophenyl)-N′-(3,3,5,5-tetramethylpiperidine-4-oxyl)-urea (DTPU). The synthesis of DTPU as well as its crystallographic data are reported. The crystal system of both compounds is monoclinic with a space group P21/c. The cell constants of DCMU are a = 7.759(1), b = 14.737(3), c = 9.233(2) Å, β = 100.99(6)°; of DTPU they are a = 6.976(1), b = 11.998(2), c = 23.585(3) Å, β = 91.38(5)°. Comparison of conformational parameters of DCMU and DTPU reveal differences in the dihedral angle between the aromatic ring and the ureido plane. The measured volumes of DCMU and DTPU are 259.1 and 493.3 Å3, respectively. These figures suggest the size of the binding site of the inhibitors in the photosynthetic membrane.
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    Stereochemistry of peptides containing 1-aminocyclopentanecarboxylic acid (Acc5): Solution and solid-state conformations of Boc-Acc5-Acc5-NHMe (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1635-1644 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformational analysis of a protected homodipeptide of 1-aminocyclopentanecarboxylic acid (Acc5) has been carried out. 1H-nmr studies establish a β-turn conformation for Boc-Acc5-Acc5-NHMe in chloroform and dimethylsulfoxide solutions involving the methylamide NH in an intramolecular hydrogen bond. Supportive evidence for the formation of an intramolecular hydrogen bond is obtained from ir studies. X-ray diffraction studies reveal a type III β-turn conformation in the solid state stabilized by a 4 → 1 hydrogen bond between the Boc CO and methylamide NH groups. The φ,ψ values for both Acc5 residues are close to those expected for an ideal 310-helical conformation (φ≃ ± 60°, ψ∼ ±30°).
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    URL: http://dx.doi.org/10.1002/bip.360250907
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    Rate constants and activation parameters for the mobility of bulk and DNA-associated glycol-water solvents (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1685-1695 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The decrease in mobility of viscous glycol-water solvents when associated with native DNA is quantified from a study of the loss of the exciting-wavelength dependence of the phosphorescence spectrum of free and bound proflavin with increasing temperature. The data are interpreted in terms of a distribution of rate constants with an Arrhenius temperature dependence. Over the temperature range of the experiments a relative decrease of ∼ 104 in the average rate constant is observed for reorientation of the solvent when associated with DNA. The basis for this large reduction is found to derive from a large decrease in the pre-exponential factors (i.e., activation entropy) associated with the reorientation rate constants. The changes in the distribution of rate constants and the activation parameters for solvent mobility induced by DNA do not resemble the changes observed for any one of a number of small ion or molecule perturbations. The results suggest the presence of disorganized, relatively immobile solvent in association with DNA.
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    Calculations on the effect of methylation on the electrostatic stability of the B- and Z-conformers of DNA (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1697-1715 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The three-dimensional Poisson-Boltzmann equation for the distribution of counterion charge density around double-helical DNA has been solved for solutions of .01M, .10M, and .20M monovalent salt. The polymers, poly[d(CpGp)] and poly[d(m5CpGp)], were studied in the B- and the Z-conformations. The effect of methylation on the relative stabilities of these conformers in solutions of different ionic strengths is known to favor the Z-form. Accumulation of charge density around the B- and the Z-conformers is compared in detail. The relative electrostatic stabilities of the B- and Z-conformers in .01M, .10M, and .20M solutions are compared and discussed in terms of the ion-DNA interactions and the self-energy of the structured ionic environment. The ion-DNA interaction energies, termed “phosphate screening,” monotonically decrease with ionic strength and are consistent with a B-to-Z conformation change induced in either polymer by increased electrolyte concentration. However, these calculated energies alone do not account for the fact that the ionic strength at the midpoint of the transition of the methylated polymer is substantially lower than that of its unmethylated analogues. The phosphate screening effect is counterbalanced by changes in the self-energy required for the creation of the structured counterion environment. This self-energy of the electrolyte environment monotonically increases with ionic strength. Methylation-induced shifts in the overall conformational equilibria depend on the relative changes of these competing effects. Increasing salt concentration is calcualted to favor the Z-conformer. The effect of methylation, lowering the ionic strength of the transition midpoint, is proposed to originate in minor structural changes in the Z-form of the polymer, making the groove more accessible to counterions in the G(3′ - 5′)C region. This allows a redistribution of counterion density and a lowering of the self-energy of the ionic environment, conferring added stability to the Z-conformation, as indicated by calculations of relative entropies. The experimentally observed temperature dependence of the B-to-Z transition, however, cannot be explained without assuming the release of bound water. Maps of the calculated three-dimensional structure at the counterion distribution near the surface of these molecules in both the B- and the Z-forms are also presented.
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    Vibrational circular dichroism spectra of three conformationally distinct states and an unordered state of poly(L-lysine) in deuterated aqueous solution (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1751-1765 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Fourier transform ir vibrational circular dichroism (VCD) spectra in the amide I′ region of poly(L-lysine) in D2O solutions have confirmed the existence of three distinct conformational states and an unordered conformational state in this homopolypeptide. Characteristic VCD spectra are presented for the right-handed α-helix, the antiparallel β-sheet, an extended helix conformation previously referred to as the so-called “random coil,” and a completely unordered conformation characterized by the absence of any amide I′ VCD. VCD for the antiparallel β-sheet in solution and the unordered chain conformation are presented for the first time. Each of the four different VCD spectra is unique in appearance and lends weight to the view that VCD has the potential to become a sensitive new probe of the secondary structure of proteins in solution.
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    URL: http://dx.doi.org/10.1002/bip.360250915
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    The hinge-bending mode of a lysozyme-inhibitor complexSupported in part by a grant from the National Institutes of Health. (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1767-1802 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The hinge-bending mode of hen egg white lysozyme is studied by a constrained minimization technique. Results with and without a bound inhibitor, tri-N-acetyl-glucosamine, are obtained. The frequency of the mode with the inhibitor is found to be 4.3 cm-1, in contrast to 3.0 cm-1 for the free enzyme. Also, the hinge-bending angle with the lowest energy is shifted 10° towards a more closed cleft in the bound species. The main contribution to these differences arise from interactions with the residues lining the cleft and those on the back side of it. Structural details that account for the energetics are presented. The method of calculation is somewhat different from a previous study [J. A. McCammon, B. R. Gelin, M. Karplus & P. G. Wolynes, (1976) Nature 262, 325-326] to reduce the likelihood of artifacts in the results.
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    Pf1 virus particle dynamics (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1859-1864 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The overall dynamics of the Pf1 filamentous bacteriophage particle in solution are characterized by nmr experiments. The chemical-shift anisotropy powder-pattern lineshapes from both DNA and protein backbone sites of the virus are motionally averaged in the same way, indicating that the entire particle undergoes rapid (〈 104 Hz) reorientation about the long axis of the filament when the virus is in solution at high pH. In contrast, the virus particles in samples at low pH are immobile on this time scale.
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    Structure and internal mobility of proteins: A molecular dynamics study of hen egg white lysozymeSupported in part by a grant from the National Institutes of Health. (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1909-1937 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The structure and internal motions of the protein hen egg white lysozyme are studied by analysis of simulation and experimental data. A molecular dynamics simulation and an energy minimization of the protein in vacuum have been made and the results compared with high-resolution structures and temperature factors of hen egg white lysozyme in two different crystal forms and of the homologous protein human lysozyme. The structures obtained from molecular dynamics and energy minimization have root-mean-square deviations for backbone atoms of 2.3 Å and 1.1-1.3 Å, respectively, relative to the crystal structures; the different crystal structures have root-mean-square deviations of 0.73-0.81 Å for the backbone atoms. In comparing the backbone dihedral angles, the difference between the dynamics and the crystal structure on which it is based is the same as that between any two crystal structures. The internal fluctuations of atomic positions calculated from the molecular dynamics trajectory agree well with the temperature factors from the three structures. Simulation and crystal results both show that there are large motions for residues involved in exposed turns of the backbone chain, relatively smaller motions for residues involved in the middle of helices or β-sheet structures, and relatively small motions of residues near disulfide bridges. Also, both the simulation and crystal data show that side-chain atoms have larger fluctuations than main-chain atoms. Moreover, the regions that have large deviations among the x-ray crystal structures, which indicates flexibility, are found to have large fluctuations in the simulation.
    Additional Material: 10 Ill.
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    The interaction of Ca2+-binding proteins with the carbocyanine dye stains-allThis study was supported by NIH Grant AM 30322-04. (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1579-1595 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The interaction of the carbocyanine dye Stains-all with the Ca2+-binding proteins calmodulin, troponin C, and parvalbumin has been monitored by means of absorption spectra and CD. In the absence of Ca2+, complexes with Stains-all of all three proteins exhibit at high dye: protein mole ratios an intense J absorption band at 600-650 nm, which is associated with a characteristic CD spectrum. In the cases of calmodulin and troponin C, the J-band is progressively lost as the dye: protein ratio decreases and is replaced by bands of the γ and β types at 450-550 nm, which likewise give rise to characteristic CD spectra. For parvalbumin, only the J-band is observed; its intensity is undiminished at the lowest dye: protein ratios examined. In the presence of excess Ca2+ the J-band is lost for all three proteins. For calmodulin and troponin C it is replaced by σ- and β-bands; in the case of parvalbumin the bound dye is released. A tentative model has been proposed to account for these observations.
    Additional Material: 11 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360250814
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    Prediction of the native conformation of a polypeptide by a statistical-mechanical procedure. II. average backbone structure of enkephalin (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1547-1563 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The average conformation of Met-enkephalin was determined by using an adaptive, importance-sampling Monte Carlo algorithm (SMAPPS - Statistical Mechanical Algorithm for Predicting Protein Structure). In the calculation, only the backbone dihedral angles (φ and ψ) were allowed to vary; i.e., all side-chain (χ) and peptide-bond (ω) dihedral angles were kept fixed at the values corresponding to a low-energy structure of the pentapeptide. The total conformational energy for each randomly generated structure of the polypeptide was obtained by summing over the interaction energies of all pairs of nonbonded atoms of the whole molecule. The interaction energies were computed by the program ECEPP/2 (Empirical Conformational Energy Program for Peptides). Solvent effects were not included in the computation. The calculation was repeated until a total of 10 independent average conformations were established. The regions of conformational space occupied by the average structures were compared with the regions of low conditional free energy obtained by SMAPPS in the first paper of this series. Such a comparison provides an analysis of the capacity of SMAPPS to adjust the Monte Carlo search to regions of highest probability. The results demonstrate that the ability of SMAPPS to focus the Monte Carlo search is excellent. Finally, the 10 independent average conformations and the mean of the 10 average structures were utilized as the initial conformations for a direct energy minimization of the pentapeptide. Of the 11 final energy-minimized structures, three of the conformations were found to be equivalent to the conformation of lowest energy determined previously. In addition, all but two of the remaining energy-minimized structures were found to correspond to one of the two other conformations of high probability obtained in the first paper of this series. These results indicate that a set of independent average conformations can provide a rational, unbiased choice for the initial conformation, to be used in a direct energy minimization of a polypeptide. The final energy-minimized structures consequently constitute a set of low-energy conformations, which include the global energy minimum.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360250812
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  • 80
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    Estimation of the stability of globular proteins (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1623-1633 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The interpretation of ΔGDH2O (the free energy change for the reaction, globular conformation ⇋ randomly coiled conformation, in the absence of denaturant), in terms of the free energies of transfer of various parts of the protein molecule from water to denaturant solution, is unsatisfactory because the latter are assumed to be identical to the transfer-free energies of similar groups attached to smaller model compounds. We have made empirical adjustments to transfer-free energy theory that make possible linear extrapolation of the free energy of denaturation of a protein from transition region to zero denaturant concentration. The modified theory, used to analyze the denaturation of proteins by guanidine hydrochloride and urea, allowed us to calculate reasonable values for Δα, the average change in accessibility to solvent of the component groups of protein.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360250906
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  • 81
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    Prediction of protein structural class from the amino acid sequenceNRCC No. 25459. (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1659-1672 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The multidimensional statistical technique of discriminant analysis is used to allocate amino acid sequences to one of four secondary structural classes: high α content, high β content, mixed α and β, low content of ordered structure. Discrimination is based on four attributes: estimates of percentages of α and β structures, and regular variations in the hydrophobic values of residues along the sequence, occurring with periods of 2 and 3.6 residues. The reliability of the method, estimated by classifying 138 sequences from the Brookhaven Protein Data Bank, is 80%, with no misallocations between α-rich and β-rich classes. The reliability can be increased to 84% by making no allocation for proteins classified with odds close to 1. Classification using previously developed secondary structural prediction methods is considerably less reliable, the best result being 64% obtained using predictions based on the Delphi method.
    Additional Material: 6 Tab.
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    URL: http://dx.doi.org/10.1002/bip.360250909
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  • 82
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    The distribution of charged groups in proteins (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1717-1733 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The distributions of charged groups in 32 proteins of known three-dimensional structure have been analyzed to determine how regularly the groups are spread over the molecule's surfaces, and to identify and to study those proteins where charge asymmetry would seem important for their function. The distributions have been analyzed in terms of charge “polarity,” surface “charge density,” and electric dipole moments. More detailed studies of the distributions for individual proteins are made using map projections specifically developed for this purpose. In the light of the results obtained we discuss the role of charged groups in relation to protein function.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360250913
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  • 83
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    Masthead (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986) 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360251001
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  • 84
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    Phosphorus nmr spectra of natural DNA fragments in the course of the B-to-A conformational transition (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1803-1812 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Changes in the 31P-nmr spectra of sonicated natural DNA fragments were investigated in ethanol solutions where the fragments underwent, as checked by CD, the B-to-A conformational transition. The study produced the following conclusions: (1) The high DNA concentrations used for the 31P-nmr measurements promote the transition compared to dilute solutions that are commonly used for CD measurements. (2) The B-to-A transition was reflected in a cooperative downfield shift of the DNA 31P-nmr resonance, consistent with unwinding of the double helix. (3) Prior to the transition, the changes in chemical shift of double-and single-stranded DNAs were almost identical. It thus appears that the effect of ethanol on the geometry and hydration of phosphodiester linkages does not depend heavily on DNA base-base interactions. (4) The A-form resonances were 30-40% narrower than the B-form resonances, which is attributed to marked sequence-dependent variations in the latter conformation and to their reduction in the former. (5) The B-form DNA aggregated in the concentrated 31P-nmr samples in the presence of ethanol, judged from a milky opalescence of the solution and a substantial broadening of its 31P-nmr resonance. The broadening abruptly disappeared as soon as DNA adopted the A-form so that DNA, in dependence on the secondary structure, showed different tendencies to condense in the presence of ethanol. The condensation increased cooperativity of the B-to-A interconversion.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360250917
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    Computer simulation of the folding-unfolding transition of island-model proteins - folding pathway, transition process, and fluctuations (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1815-1835 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Monte Carlo computer simulations were performed to elucidate the dynamic aspects of the folding and unfolding transitions of island-model protein. Five different types of model proteins were designed, according to characteristics of backbone structure. The computer simulations clearly show that the unfolding and folding transitions are all-or-none processes between the N-and U-states. They are typical Poisson processes. From the Arrhenius plots of rate constants, the activation enthalpies of folding and unfolding were determined. In addition, the folding pathways were determined along the reaction coordinate. Formations of several local structures along a polypeptide chain are almost simultaneous, but the most probable time sequence of events exists at the moment of transition. That is the most probable folding pathway. The unfolding pathway was found to be just the reverse process of the most probable folding pathway. The relationship between the fluctuations in each equilibrium state and the transition process was considered. In contrast to the theory of absolute reaction rate, the transient states are widely distributed along the reaction coordinate. From analysis of the “transient process,” we tried to determine the critical states from which the transient process starts. As a result, we found that the unfolding transition occurs at the stage near the N-state. During the U-state, large joined blocks rarely appear, but they appear in the transient process towards the N-state. However, the “branch point” between the N- and U-states lies near the N-state, and joined blocks tend to unfold prior to passing over the branch point. We concluded that the stability of later folding intermediates is important for selection of the folding pathway, while preferential selection of an early folding intermediate is important in acceleration of the folding rate. The effects of intrachain cross-linking and peptide fragment binding on the rate constants were examined by using computer simulations of model proteins. In general, a small-sized loop formed by cross-linking accelerates the folding rate and a large-sized loop contributes much to the stabilization of the native conformation. We also found that peptide fragment binding contributes little to the acceleration of the folding rate of the residual protein.
    Additional Material: 11 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360251002
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    Multiple denaturational transitions in fibrillar collagen (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 1875-1893 
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    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The heat denaturation of pepsinized bovine nonfibrillar and fibrillar collagen was studied by differential scanning calorimetry. For fibrillar preparations that had been rapidly precipitated with stirring at low ionic strength, then resuspended at physiological ionic strength, multiple denaturational transitions were observed. At heating rates of 10°C/min, melting endotherms occurred at about 44, 50, 53, and 57°C. Fibrillar collagen that was slowly gelled without stirring at physiological ionic strength exhibited a similar series of endotherms, but the lower melting transitions were less conspicuous. In contrast, nonfibrillar bovine collagen in acidic solution showed only a single denaturational transition at 40°C. Nonfibrillar solutions at pH 7, to which inhibitors of fibrillogenesis were added, showed a major endotherm as high as 46°C. These results suggest that reconstituted fibrillar collagen contains a heterogeneous fibril population, possibly including molecules in a nonfibrillar state. It was proposed that the multiple melting endotherms of such preparations were due to sequential melting of molecular and fibril classes, each with a distinct melting temperature. The fibrillar classes may represent three or more types of banded and nonbanded species that differ from each other in packing order, collagen concentration, and possibly also in fibril width and level of cross-linking.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360251006
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  • 87
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    Gramicidin S analogs with a D-Ala, Gly, or L-Ala residue in place of the D-Phe residue: Molecular conformations and interactions with phospholipid membrane (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 2295-2307 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The proton nmr and CD spectra of gramicidin S (GS) cyclic-(Val1,1′-Orn2,2′-Leu3,3′-D-Phe4,4′-Pro5,5′)2 and of GS analogs - namely, [D-Ala4,4′]-GS, [Gly4,4′]-GS, and [L-Ala4,4′]-GS - were analyzed. The molecular conformation of [D-Ala4,4′]-GS is similar to that of GS, with the trans form about the D-Ala-Pro peptide bond. The molecular conformation of [Gly4,4′]-GS depends on the solvent composition of dimethylsulfoxide-d6/trifluoroethanol (DMSO)-d6/TFE and DMSO-d6/H2O as well as the solute concentration. In DMSO-d6 solution, [Gly4,4′]-GS forms the GS-type conformation of the monomer at lower concentration. At higher concentration, the GS-type conformer is converted to the other one that forms molecular aggregates. The cis form about the X-Pro peptide bonds is found for [Gly4,4′]-GS and [L-Ala4,4′]-GS in DMSO-d6 and for [L-Ala4,4′]-GS in TFE solution. The large temperature dependences of α-proton chemical shifts of [L-Ala4,4′]-GS in DMSO-d6 solution indicate that the conformer equilibrium changes with temperature. The GS-type conformation is not formed in [L-Ala4,4′]-GS. The two active peptide analogs, [D-Ala4,4′]-GS and [Gly4,4′]-GS, interact with the phospholipid membrane, taking the GS-type conformation. By contrast, an inactive analog, [L-Ala4,4′]-GS, does not interact with phospholipid membrane. The activities of GS analogs are found to correlate to the formation of the GS-type conformation upon binding with phospholipid membrane.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360251207
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  • 88
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    Lateral packing of protofibrils in fibrin fibers and fibrinogen polymers (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 2359-2373 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The distinctive transverse banding pattern of fibrin fibers clearly indicates ordering of molecules in the longitudinal direction. In this study we examined the fibers of fibrin clots, as well as two types of fibrinogen polymers, by thin-section electron microscopy. The fibrinogen polymers have a transverse banding pattern identical to that of fibrin fibers - clearly indicating a regular longitudinal repeat - but they are larger in diameter, and show little or no branching. We therefore expected their overall ordering to be better than that of fibrin fibers. Several different fixation protocols were used. We readily observed the typical transverse banding seen previously by negative stain and metal replication techniques. However, only very rarely was any regular lateral lattice seen in any of the samples. X-ray diffraction was used to examine unfixed specimens of the two fibrinogen polymers and, once again, although a longitudinal repeat was evident, only rarely was evidence for lateral crystallinity seen. The electron-microscope and x-ray results showed that the needles and pellet fibers of fibrinogen have essentially the same internal architecture as thick fibrin fibers, and that all three types of polymer, although clearly transversely banded, have almost no crystallinity in their lateral protofibril packing.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360251213
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  • 89
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    Binding of porcine pancreatic secretory trypsin inhibitor to bovine β-trypsin: A kinetic study (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 2325-2333 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of the formation of the complex between bovine β-trypsin and the porcine pancreatic secretory trypsin inhibitor (PSTI; Kazal-type inhibitor) was investigated following the spectral changes associated with the displacement of proflavine from the enzyme, upon inhibitor binding, between pH 3.5 and 8.0 (I = 0.1M) at 21 ± 0.5°C. With inhibitor in excess over the enzyme ([PSTI] ≥ 5 × [bovine β-trypsin]), the time course of the reaction corresponds to a pseudo-first-order process. Over the whole pH range explored, the concentration dependence of the rate is second order at low PSTI concentrations but tends to first order at high inhibitor concentrations. This behavior may be explained by a relatively fast pre-equilibrium followed by a limiting first-order process. Values of kinetic parameters for PSTI binding to bovine β-trypsin depend, between pH 3.5 and 8.0, on the acid-base equilibrium of a single ionizing group (probably His-57 of bovine β-trypsin) that undergoes an acidic pKa shift from 7.0 in the free bovine β-trypsin to 5.5 in the enzyme:PSTI complex. Kinetics of the bovine β-trypsin:PSTI adduct formation has been analyzed and compared with that of other (pro)enzyme:inhibitor reactions. Considering the known molecular structures of free serine (pro)enzymes, of Kazal- and Kunitz-type inhibitors, as well as of their complexes, the binding behavior of PSTI to bovine β-trypsin has been related to the inferred stereochemistry of the proteinase:inhibitor contact region.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360251210
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  • 90
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    Masthead (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986) 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360250101
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  • 91
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    The relation of ion pairs to protein hydration: An IR spectroscopic and X-ray crystallographic survey (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 317-335 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We report here a novel ir technique that we use to determine the apparent van't Hoff's energy for the distillation of water from protein amide and acid groups. The method is used to study the hydration properties of ten different proteins. The results show that water removal from the environment of ion-paired acid groups (those ≤ 4 Å from a basic group on the protein surface) requires less energy than water removal from the environment of nonpaired acid groups. These observations are supported by an analysis of the solvent distributions in protein crystal structures. A model is proposed for the interaction between water and protein acid groups, and this model is used to account for the distributions and properties of certain eye-lens proteins.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360250212
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  • 92
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    A polynucleotide CD probe: Interactions with oligomers of a polycationic amine that exhibit positive extrinsic bands at 〉 300 nm (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 407-429 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A set of large positive extrinsic CD bands ([θ]333 = 2.6 X 104 deg-cm2/decimole phosphate) in the 〉 300 nm region as well as diminution of the intrinsic signals (θ275) have been observed in the CD spectra of various nucleic acids complexed with the achiral compound, N-poly{α-[N-(4-pyridylethylene-4-pyridyl-N′-)α′-p-xylyl]dibromide}-4-pyridylethylene-4-pyridinium bromide, (polymer X).1,2,5 The signal changes are attributed to the binding of polymer X chromophores isogeometrically to the DNA helix in an ordered chiral arrangement. Fractionation of polymer X gives 10 well-separated oligomers. The oligomers were characterized by nmr. Their interactions with DNA have been investigated with respect to r(r = ratio of equivalents of polymer X charge/g-atoms DNA phosphorus) and n (oligomer chain length). In all cases where n ≥ 1, [θ]333 increases linearly with increasing r between 0 and 0.32, and is accompanied by a corresponding decrease in [θ]275, which becomes negative as r approaches .32. Extrinsic band intensities reveal a dependence on n up to n = 5, above which increases in nonspecific binding result in a reduction in normalized band intensities. Polymer X shows a strong preference for B-form nucleic acids and induces maximum extrinsic CD signal intensities with A-T homopolymers. Alterations in helix hydration are believed to accompany complex formation. Inversions in [θ]275 of the octamer X-poly(dA-dT) complex have been attributed to the “alternating B” conformation of poly(dA-dT).3 Similar inversions are not observed in other nucleic acid-octamer X complexes. Visible and CD spectrometry data from competition studies in the presence of the antibiotics actinomycin D (AMD), daunomycin (DM), and distamycin A (DST) are consistent with “nonclassical” intercalation as the mode of binding, and these data place the potential binding site in or near the hydrophobic region of the minor groove. Reductions in [θ]333 with increasing urea further implicate the involvement of hydrophobic interactions in the formation of an asymmetric complex. Stabilization of the helix results in all cases as evidenced by alterations in Tm; corresponding changes, however, in cooperativity are not clearly discernable. Viscosity and light-scattering data indicate no changes in molecular weight due to aggregation, and as such are not consistent with a transition to the ψ-DNA upon complex formation.
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    URL: http://dx.doi.org/10.1002/bip.360250304
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    Vacuum UV CD of the low-salt Z-forms of poly(rG-dC)·poly(rG-dC), and poly(dG-m5dC)·poly(dG-m5dC) (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 519-523 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The vacuum CD spectra of poly(rG-dC)·poly(rG-dC) and poly(dG-m5dC)·poly(dG-m5dC) have been obtained for the low-salt Z-conformations of both polymers. The spectra are very similar to those for the high-salt Z-forms. This behavior is consistent with the suggestion that the low- and high-salt Z-forms are comprised of different proportions of ZI- and ZII-conformations.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360250310
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  • 94
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    Chain association of pectic molecules during calcium-induced gelationPart of this work has been presented at the 7th European Polymer Network Group Meeting, September 10-14, 1984, Manchester, England. (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 455-468 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The chain association of pectic molecules with different levels and patterns of esterification during calcium-induced gelation was studied by methods such as light scattering, viscometry, and determination of calcium activity coefficient and of calcium transport parameter. A gel point can be determined, assuming a power law including a critical ratio (equivalent concentration of calcium ions/pectin carboxylic groups) and quasi-critical exponents varying in the range 0.50-1.26. The values of these critical parameters were discussed as a function of polymer concentration, of level and pattern of esterification, and of the nature of the divalent counterion. The lower these values are, the better, apparently, the gel-forming ability of the pectins is.
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    URL: http://dx.doi.org/10.1002/bip.360250306
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  • 95
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    Models of thioredoxin hairpin structures: Conformational properties of β-turn containing sequences (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 555-570 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Sequences 74-91 and 77-91 of E. coli thioredoxin, which according to x-ray structure contain an irregular β-turn, a hairpinlike structural element, have been synthesized and their conformational properties in solution have been investigated by means of CD spectroscopy. In addition, analogs of these sequences, containing the regular β-turn element Gly-Pro-(Gly)2, have also been prepared and investigated. These are BOC-Ile-Gly-Pro-(Gly)2-Val-OMe (III) and BOC-(Ile)3Gly-Pro-(Gly)2-(Val)5-OMe (IV) that on the basis of probability, should form hairpin structures stabilized by intramolecular interactions. While the natural sequences were shown to be unable to adopt structures characterized by an intrinsic conformational stability, the two analogs showed evidence of intramolecular folding in methanol and trifluoroethanol-water solution. In particular, the CD spectra are indicative of β-structure. The most interesting case was observed for compound IV, as the highest degree of conformational order was present in solutions containing a large proportion of water. In addition, the formation of this structure took place in a highly cooperative manner. The results are utilized to discuss whether and to what extent conformationally stable folding peptide units of small size can be formed in aqueous solution.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360250404
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  • 96
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    Halogenated nucleic acids: Effects of 5-fluorouracil on the conformation and properties of a polyribonucleotide and its constituentsThis investigation was supported by PHS Grant number CA-25438, awarded by the National Cancer Institute, DHHS. (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 571-600 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformational properties of 5-fluorouracil derivatives are compared to uracil derivatives. FUrd, 5′-FUMP, and poly(FU) are studied as a function of pH and temperature by 19F- and 1H-nmr spectroscopy, and the corresponding uracil derivatives by 1H-nmr spectroscopy. FUrd exhibits no significant conformational changes with solution pH (5-10). In contrast, at low pH (6-7) 5′-FUMP and 5′-UMP show similar conformational features, while at high pH (9) 5′-FUMP shows significant conformational alterations. Also, poly(U) and poly(FU) are conformationally similar at low pH, but increasing pH induces changes in poly(FU). These changes are observed in the backbone [γ(C4′-C5′)], furanose, and furanose-base conformations. The apparent pKa of N3-H ionization of the FUra base is determined by 1H- and 19F-nmr to range from 7.5 to 8.2 [FUrd 〈 5′-FUMP 〈 5′-FUDP 〈 poly(FU)]. These observations are interpreted as a result of electrostatic interactions generated between the ionized phosphate group and the negatively charged base moiety as the pH is raised. The interaction properties of poly(FU) with ApA are studied by 1H- and 19F-nmr spectroscopy, and these properties compared to those published for poly(U). Poly(FU) forms a complex with ApA inducing upfield 1H-shifts in both components, and downfield 19F- shifts in poly(FU). The base stoichiometry of the complex for poly(U)·ApA is 2U:1A at various U/A ratios. In contrast, the base stoichiometry of the poly(FU)·ApA complex appears to be dependent on the FU/A ratio. At high FU/A ratio, the complex is 2FU:1A, and as the FU/A ratio approaches unity the complex becomes 1FU:1A.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360250405
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  • 97
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    Sequential polypeptides containing arginine as histone models: Synthesis and conformational studies (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 655-675 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The sequential polypeptides (L-Arg-X-Gly)n, where X represents amino acid residues Ala, Val, and Leu, were prepared as models of arginine-rich histones to be used in studying their structure and their interactions with DNA. The polymerization was carried out on the pentachlorophenyl active esters of the appropriate tripeptides, while the toluene-4-sulfonyl group was used for protecting the arginine guanido group. CD was employed to investigate the conformation of (L-Arg-X-Gly)n polymers in aqueous solutions, at different pH, as well as in trifluoroenthanol and hexafluoroisopropyl alcohol solutions. In aqueous solutions (at pH 7 and 12) the prepared sequential polymers behaved as a random coil. The CD spectra in various trifluoroethanol-water or hexafluoroisopropyl alcohol-water mixtures indicated that the degree of helical conformation of the studied polytripeptides increased in the order of Ala → Val → Leu. The opposite was true for the β-structure. Characteristics of β-turn are excluded from the poly(L-Arg-L-Leu-Gly), which assumed the most pronounced helical conformation. The poly(L-Arg-L-Val-Gly) exerts a significant preference to the β-turn structure compared to that of poly(L-Arg-L-Ala-Gly). Thus the probability for helical, β-structure or β-turn conformations of the polymers was analyzed in relation to the bulkiness and length, and to the special features of the X-residue side chain (β-branching). We concluded that the prepared sequential arginine-containing polypeptides are plausible models for histone fractions, f3 and f2α1.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360250410
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  • 98
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    Specific assignment of resonances in the 1H-nmr spectrum of the polypeptide toxin I from Anemonia sulcata (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 489-506 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The assignment of a large number of resonances in the 300-MHz 1H-nmr spectrum of the polypeptide neurotoxin Anemonia sulcata toxin I is described. The initial identification of spin systems is made using both one- and two-dimensional nmr spectra. The subsequent assignment of these spin systems to specific residues in the molecule is based largely on the observation in two-dimensional spectra of through-space connectivities between Hα and NH resonances from adjacent residues in the amino acid sequence. Using these techniques, the full spin systems of 22 residues are specifically assigned, together with partial assignments for a further 8. Many of the spin systems from the remaining 16 residues have been defined, although not yet specifically assigned. From the pattern of through-space connectivities between protons from adjacent residues in the sequence, some inferences may be drawn concerning the secondary structure of this polypeptide in aqueous solution.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360250308
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  • 99
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    Electronic Resource
    Masthead (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986) 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360250401
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  • 100
    Electronic Resource
    Electronic Resource
    Macroscopic polarity of connective tissue is due to discrete polar structures (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 601-606 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Applying scanning optical harmonic microscopy to biological tissue for the first time, we have discovered that the macroscopic polarity of rat-tail tendon is due to a coherent network of discrete polar structures. This finding permits isolation of these structures for further detailed analysis, which should lead to their complete characterization and thus to a solution of the twenty-year-old mystery of connective tissue polarity.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360250406
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