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  • 1
    Electronic Resource
    Electronic Resource
    Molecular modeling of human MT2 melatonin receptor: the role of Val204, Leu272 and Tyr298 in ligand binding (2004)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 91 (2004), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: A model of the helical part of the human MT2 melatonin (hMT2) receptor, a member of the G protein-coupled receptors superfamily has been generated, based on the structure of bovine rhodopsin. Modeling has been combined with site-directed mutagenesis to investigate the role of the specific amino acid residues within the transmembrane domains (TM) numbers V, VI and VII of hMT2 receptor in the interaction with 2-iodomelatonin. Saturation binding assays with 2-iodomelatonin demonstrated that the substitution V204A (TMV) resulted in total loss of binding while the mutation V205A had no effect. The replacement of F209 with alanine led to a significant decrease in the Bmax value of receptor binding while mutations V205A and F209A also within TM V did not significantly change binding properties of the hMT2 receptor. In the case of TM VI, the substitution G271T caused substantial decrease in 2-iodomelatonin binding to the hMT2 receptor. The change L272A (TM VI) as well as mutation Y298A within TM VII completely abolished ligand binding to the receptor. These data suggest that several new amino acid residues within TM V, VI and VII are involved in ligand–MT2 receptor interaction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.2004.02758.x
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  • 2
    Electronic Resource
    Electronic Resource
    ERRATUM: Molecular modeling of human MT2 melatonin receptor: the role of Val204, Leu272 and Tyr298 in ligand binding (2004)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 91 (2004), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.2004.02965.x
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  • 3
    Electronic Resource
    Electronic Resource
    δ-Opioid receptors exhibit high efficiency when activating trimeric G proteins in membrane domains (2003)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 85 (2003), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Low-density membrane fragments (domains) were separated from the bulk of plasma membranes of human embryonic kidney (HEK)293 cells expressing a δ-opioid (DOP) receptor-Gi1α fusion protein by drastic homogenization and flotation on equilibrium sucrose density gradients. The functional activity of trimeric G proteins and capacity of the DOP receptor to stimulate both the fusion protein-linked Gi1α and endogenous pertussis-toxin sensitive G proteins was measured as d-Ala2, d-Leu5-enkephalin stimulated high-affinity GTPase or guanosine-5′-[γ-35S]triphosphate ([35S]GTPγS) binding. The maximum d-Ala2-d-Leu5 enkephalin (DADLE)-stimulated GTPase was two times higher in low-density membrane fragments than in bulk of plasma membranes; 58 and 27 pmol/mg/min, respectively. The same difference was obtained for [35S]GTPγS binding. Contrarily, the low-density domains contained no more than half the DOP receptor binding sites (Bmax = 6.6 pmol/mg versus 13.6 pmol/mg). Thus, when corrected for expression levels of the receptor, low-density domains exhibited four times higher agonist-stimulated GTPase and [35S]GTPγS binding than the bulk plasma membranes. The regulator of G protein signaling RGS1, enhanced further the G protein functional activity but did not remove the difference between domain-bound and plasma membrane pools of G protein. The potency of the agonist in functional studies and the affinity of specific [3H]DADLE binding to the receptor were, however, the same in both types of membranes – EC50 = 4.5 ± 0.1 × 10−8 and 3.2 ± 1.4 × 10−8 m for GTPase; Kd = 1.2 ± 0.1 and 1.3 ± 0.1 nm for [3H]DADLE radioligand binding assay. Similar results were obtained when sodium bicarbonate was used for alkaline isolation of membrane domains. By contrast, detergent-insensitive membrane domains isolated following treatment of cells with Triton X100 exhibited no DADLE-stimulated GTPase or GTPγS binding. Functional coupling between the DOP receptor and cognate G proteins was also blocked by high-energy ultrasound and repeated freezing-thawing. Our data indicate, for the first time, that membrane domains isolated using ‘detergent-free’ procedures exhibit higher efficiency of coupling between a G protein-coupled receptor and its corresponding G protein(s) than bulk plasma membranes. Detergent-extraction diminishes these interactions, even when the receptor and G proteins are physically tethered together.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.2003.01667.x
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  • 4
    Electronic Resource
    Electronic Resource
    Light-Scattering and TEM Analyses of Virtual Upper Critical Solution Temperature Behavior in PCL/SAN Blends (1994)
    s.l. : American Chemical Society
    Macromolecules 27 (1994), S. 1154-1159 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00083a012
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  • 5
    Electronic Resource
    Electronic Resource
    Time-resolved fluorescence study of chain dynamics. 1. Poly(methacrylic acid) in dilute water solutions (1991)
    s.l. : American Chemical Society
    Macromolecules 24 (1991), S. 2054-2059 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00008a053
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  • 6
    Electronic Resource
    Electronic Resource
    Maturation of rat brain is accompanied by differential expression of the long and short splice variants of Gsα protein: identification of cytosolic forms of Gsα (2001)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 79 (2001), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Distribution of the α subunit of the stimulatory G protein (Gsα) was analyzed in membrane and cytosolic (supernatant 200 000 g) fractions from rat cortex, thalamus and hippocampus during the course of post-natal development. In parallel, changes in β-adrenoceptor density and adenylyl cyclase activity were determined. Long (GsαL) and short (GsαS) variants of Gsα were assessed by immunoblotting using specific polyclonal antisera reacting with both Gsα isoforms. Post-natal development was associated with an increase in the total amount of brain Gsα. GsαL was the dominant isoform of Gsα in the membrane fractions of all studied brain regions and its amount increased markedly between post-natal day (PD) 1 and 90. The level of membrane-bound GsαS also elevated during post-natal development, but more pronounced changes were found in cytosolic GsαS. Although only a small amount of GsαS (much smaller than GsαL) was detected among soluble proteins shortly after birth, GsαS prevailed over GsαL at PD90. The GsαL/GsαS ratio decreased, respectively, from 3.2 to 1.2 and from 5.0 to 1.5 in the membrane fractions of cortex and hippocampus, but remained almost constant in thalamus between PD1 and 90. More dramatic changes were found in the cytosolic fractions of all studied brain regions: the GsαL/GsαS ratio decreased sharply in cortex (from 14.1 to 0.9), hippocampus (from 3.7 to 0.8), and also in thalamus (from 9.5 to 0.5). These results demonstrate that the membrane–cytosol balance of Gsα proteins alters dramatically during the course of brain development. Both GsαL and GsαS were expressed in a region- and age-specific manner, which suggests different roles in the maturation of the brain tissue. A cyc− reconstitutive assay of cytosolic Gsα indicated that only ≈ 20% of this protein was functional, compared with membrane-bound Gsα, and its ability to reconstitute adenylyl cyclase activity increased during the course of maturation. The number of β-adrenoceptors increased sharply during early post-natal development but only slightly in adulthood, and both GTP- and isoproterenol-stimulated adenylate cyclase activity reached peak values around PD12.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.2001.00544.x
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  • 7
    Electronic Resource
    Electronic Resource
    Different sensitivity of ATP + Mg + Na (I) and Pi + Mg (II) dependent types of ouabain binding to phospholipase A2 (1988)
    Springer
    The journal of membrane biology 104 (1988), S. 211-221 
    Details
    ISSN: 1432-1424
    Keywords: ouabain binding ; phospholipase A2 ; Na,K-ATPase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The effect of phospholipase A2 and of related agents on ouabain binding and Na,K-ATPase activity were studied in intact and detergent-treated membrane preparations of rat brain cortex and pig kidney medulla. It was found that phospholipase A2 (PLA2) may distinguish or dissociate ouabain binding complexes I (ATP+Mg+Na) and II (Pi+Mg), stimulating the former and inhibiting the latter. Procedures which break the permeability barriers of vesicular membrane preparations, such as repeated freezing-thawing, sonication or hypoosmotic shock failed to mimic the effect of PLA2, indicating that it was not acting primarily by opening the inside-out oriented vesicles. The detergent digitonin exhibited similar effects on ouabain binding in both ATP+Mg+Na and Pi+Mg media. Other detergents were ineffective. The ability of PLA2 to distinguish between ouabain binding type I and II can be manifested even in SDS-treated, purified preparations of Na,K-ATPase. The number of ATP+Mg+Na-dependent sites is unchanged, while the Pi+Mg-dependent sites are decreased in number in a manner similar to that seen in original membranes. This inhibition is completely lost in the reconstituted Na,K-ATPase system, where the ATP- as well as Pi-oriented ouabain sites are inhibited by PLA2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01872323
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  • 8
    Electronic Resource
    Electronic Resource
    On the mechanism of catecholamine-induced hyperpolarization of skeletal muscle cells (1985)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 329 (1985), S. 18-23 
    Details
    ISSN: 1432-1912
    Keywords: Noradrenaline ; Hyperpolarization ; Electrogenic Na+/K+ pump ; Ca2+-activated K+-channel ; Mouse diaphragm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 1. Catecholamines (noradrenaline, adrenaline and isoprenaline) were tested for their effect on the resting membrane potential of mouse skeletal muscle cells. In freshly isolated muscles incubated in the normal solution containing 5 mol · l−1, catecholamines increased the resting membrane potential (RMP) by 3–5 mV. In Na+-loaded muscles incubated in a K+-free solution, however, catecholamines increased the RMP by 13–16 mV; consequent application of K+ to these muscles did not hyperpolarize the membrane further. A significant decrease of input membrane resistance was observed during the noradenaline-induced hyperpolarization. This indicates that the passive membrane permeability for K+ ions was apparently increased. Noradrenaline-induced hyperpolarization requires the presence of calcium ions in the incubation solution. We therefore assume that catecholamines hyperpolarize the membrane by Ca2+-dependent K+-channels activation. 2. The action of catecholamines on the resting membrane potential of skeletal muscle exhibits a 50% nonspecific effect as far as the adrenergic receptor is concerned, and the rest may be blocked by adrenergic blocking agents.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00695186
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  • 9
    Electronic Resource
    Electronic Resource
    Modification of polyamide 6 with hycar ATBN (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 178 (1990), S. 85-93 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Es wurde die Synthese von Blockcopolymeren aus 6-Caprolactam und einem flüssigen aminotelechelischen Copolymeren aus 1,3-Butadien und Acrylnitril (Hycar ATBN 1300X21) studiert, die eine höhere Kerbschlagzähigkeit als das geläufige Poly(6-caprolactam) aufweisen. Bei der durch das Addukt aus Phosphorsäure und 6-Caprolactam initiierten Polymerisation von 6-Caprolactam wurde der Einfluß der Konzentration des Initiators (0-5 mol-%) und der Konzentration von Hycar ATBN 1300X21 (0-50 Gew.-%) im Polymerisationsgemisch, der Zeit (4-72 h) und der Temperatur (200-280°C) auf den Umsatz von 6-Caprolactam sowie auf die Eigenschaften des entstandenen Copolymeren untersucht. Die unter optimierten Bedingungen dargestellten Blockcopolymeren wiesen eine Kerbschlagzähigkeit von 13,5 kJ·m-2 auf.
    Notes: The preparation of block copolymers from 6-caprolactam and a liquid amine terminated butadiene-acrylonitrile copolymer Hycar ATBN 1300X21 having higher notched impact strength than ordinary poly(6-caprolactam) was studied. In the polymerization of 6-caprolactam initiated by an adduct of phosphoric acid with 6-caprolactam the influence of initiator concentration (0- 50 mol-%) and Hycar ATBN 1300X21 concentration (0-5 wt.-%) in the polymerization charge, of polymerization time (4 - 72 h) and of temperature (200-280°C) on the 6-caprolactam conversion and on the properties of the copolymers formed were followed. Notched impact strength of the block copolymers prepared under optimized conditions was as high as 13.5 kJ·m-2.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051780106
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