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Digitale Medien

Modelling and mutation studies on the histamine H1-receptor agonist binding site reveal different binding modes for H1-agonists: Asp116 (TM3) has a constitutive role in receptor stimulation (1995)

Laak, Anton M. ; Timmerman, Hendrik ; Leurs, Rob ; [weitere]

Springer

Journal of computer aided molecular design 9 (1995), S. 319-330

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ISSN: 1573-4951

Schlagwort(e): Histamine ; H1-receptor ; H1-agonists ; H1-antagonists ; G-protein coupled receptor

Quelle: Springer Online Journal Archives 1860-2000

Thema: Chemie und Pharmazie

Notizen: Summary A modelling study has been carried out, investigating the binding of histamine (Hist), 2-methylhistamine (2-MeHist) and 2-phenylhistamine (2-PhHist) at two postulated agonistic binding sites on transmembrane domain 5 (TM5) of the histamine H1-receptor. For this purpose a conformational analysis study was performed on three particular residues of TM5, i.e., Lys200, Thr203 and Asn207, for which a functional role in binding has been proposed. The most favourable results were obtained for the interaction between Hist and the Lys200/Asn207 pair. Therefore, Lys200 was subsequently mutated and converted to an alanine, resulting in a 50-fold decrease of H1-receptor stimulation by histamine. Altogether, the data suggest that the Lys200/Asn207 pair is important for activation of the H1-receptor by histamine. In contrast, analogues of 2-PhHist seem to belong to a distinct subclass of histamine agonists and an alternative mode of binding is proposed in which the 2-phenyl ring binds to the same receptor location as one of the aromatic rings of classical histamine H1-antagonists. Subsequently, the binding modes of the agonists Hist, 2-MeHist and 2-PhHist and the H1-antagonist cyproheptadine were evaluated in three different seven-α-helical models of the H1-receptor built in homology with bacteriorhodopsin, but using three different alignments. Our findings suggest that the position of the carboxylate group of Asp116 (TM3) within the receptor pocket depends on whether an agonist or an antagonist binds to the protein; a conformational change of this aspartate residue upon agonist binding is expected to play an essential role in receptor stimulation.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00125173

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Digitale Medien

The agonistic binding site at the histamine H2 receptor. II. Theoretical investigations of histamine binding to receptor models of the seven α-helical transmembrane domain (1996)

Nederkoorn, Paul H. J. ; Gelder, Erna M. ; Donné-Op den Kelder, Gabriëlle M. ; [weitere]

Springer

Journal of computer aided molecular design 10 (1996), S. 479-489

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ISSN: 1573-4951

Schlagwort(e): G-protein-coupled receptor ; Hartree-Fock calculations ; Histamine H2 receptor ; Molecular mechanics ; Receptor models

Quelle: Springer Online Journal Archives 1860-2000

Thema: Chemie und Pharmazie

Notizen: Summary In the first part (pp. 461–478 in this issue) of this study regarding the histamine H2 receptor agonistic binding site, the best possible interactions of histamine with an α-helical oligopeptide, mimicking a part of the fifth transmembrane α-helical domain (TM5) of the histamine H2 receptor, were considered. It was established that histamine can only bind via two H-bonds with a pure α-helical TM5, when the binding site consists of Tyr182/Asp186 and not of the Asp186/Thr190 couple. In this second part, two particular three-dimensional models of G-protein-coupled receptors previously reported in the literature are compared in relation to agonist binding at the histamine H2 receptor. The differences between these two receptor models are discussed in relation to the general benefits and limitations of such receptor models. Also the pros and cons of simplifying receptor models to a relatively easy-to-deal-with oligopeptide for mimicking agonistic binding to an agonistic binding site are addressed. Within complete receptor models, the simultaneous interaction of histamine with both TM3 and TM5 can be analysed. The earlier suggested three-point interaction of histamine with the histamine H2 receptor can be explored. Our results demonstrate that a three-point interaction cannot be established for the Asp98/Asp186/Thr190 binding site in either of the investigated receptor models, whereas histamine can form three H-bonds in case the agonistic binding site is constituted by the Asp98/Tyr182/Asp186 triplet. Furthermore this latter triplet is seen to be able to accommodate a series of substituted histamine analogues with known histamine H2 agonistic activity as well.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00124477

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Digitale Medien

Hybrid-hybrid matrix structural refinement of a DNA three-way junction from 3D NOESY-NOESY (1999)

Thiviyanathan, Varatharasa ; Luxon, Bruce A. ; Leontis, Neocles B. ; [weitere]

Springer

Journal of biomolecular NMR 14 (1999), S. 209-221

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ISSN: 1573-5001

Schlagwort(e): MORASS ; NOESY-NOESY ; relaxation matrix analysis ; three-way junction

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie , Chemie und Pharmazie

Notizen: Abstract Homonuclear 3D NOESY-NOESY has shown great promise for the structural refinement of large biomolecules. A computationally efficient hybrid-hybrid relaxation matrix refinement methodology, using 3D NOESY-NOESY data, was used to refine the structure of a DNA three-way junction having two unpaired bases at the branch point of the junction. The NMR data and the relaxation matrix refinement confirm that the DNA three-way junction exists in a folded conformation with two of the helical stems stacked upon each other. The third unstacked stem extends away from the junction, forming an acute angle (∼60° ) with the stacked stems. The two unpaired bases are stacked upon each other and are exposed to the solvent. Helical parameters for the bases in all three strands show slight deviations from typical values expected for right-handed B-form DNA. Inter-nucleotide imino-imino NOEs between the bases at the branch point of the junction show that the junction region is well defined. The helical stems show mobility (± 20° ) indicating dynamic processes around the junction region. The unstacked helical stem adjacent to the unpaired bases shows greater mobility compared to the other two stems. The results from this study indicate that the 3D hybrid-hybrid matrix MORASS refinement methodology, by combining the spectral dispersion of 3D NOESY-NOESY and the computational efficiency of 2D refinement programs, provides an accurate and robust means for structure determination of large biomolecules. Our results also indicate that the 3D MORASS method gives higher quality structures compared to the 2D complete relaxation matrix refinement method.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1023/A:1008330011425

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Digitale Medien

Mikrostrukturelle, mechanische und korrosive Eigenschaften reibrührgeschweißter Stumpfnähte in Aluminiumlegierungen (1998)

Donne, C. Dalle ; Braun, R. ; Staniek, G. ; [weitere]

Weinheim : Wiley-Blackwell

Materialwissenschaft und Werkstofftechnik 29 (1998), S. 609-617

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ISSN: 0933-5137

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Maschinenbau

Beschreibung / Inhaltsverzeichnis: Microstructural, mechanical and corrosive properties of friction stir welded aluminium jointsFriction stir welding (FSW) is a novel solid state welding process. It allows joining of high strength aluminum alloys, generally considered as difficult-to-weld with conventional technologies, without loss in joint strength. Results of investigations on selfmade FSW butt joints of the aluminum alloys 2024-T3 and 6013-T4 are presented. First, the microstructure of the weld seam and heat affected zone is characterised metallographically and by hardness measurements. By tensile, fatigue endurance (SN) and fatigue crack propagation tests it is demonstrated, that especially the FSW-joints of 2024-T3 sustain high mechanical loadings. Investigations on the corrosion properties reveal a certain sensitivity of the 2024-T3 joints to intergranular and exfoliation corrosion.

Notizen: Das Reibrührschweißen (friction stir welding FSW) ist ein neues Fügeverfahren, mit dem auch die schwer schmelzschweißbaren, höherfesten Aluminiumlegierungen ohne große Festigkeitsverluste verschweißt werden können. Erste Ergebnisse von Untersuchungen an selbst hergestellten FSW-Stumpfnähten der Aluminiumlegierungen 2024-T3 und 6013-T4 werden vorgestellt. Zunächst wird das Gefüge der Naht und der Wärmeeinflußzone mikrostrukturell und durch Härteverläufe charakterisiert. Weiterhin wird mit Zug-, Schwingfestigkeits- und Rißfortschrittsversuchen nachgewiesen, daß insbesondere die FSW-Nähte der Legierung 2024-T3 außerordentlich hohe mechanische Belastungen ertragen. Abschließende Korrosionsuntersuchungen der FSW-Nähte zeigen eine gewisse Anfälligkeit der abschreckempfindlichen Legierung 2024-T3 für interkristalline Korrosion und Schichtkorrosion.

Zusätzliches Material: 15 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/mawe.19980291012

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