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  • 1
    Electronic Resource
    Electronic Resource
    Isomerization of the Xaa-Pro peptide bond induced by ionic interactions of arginine (1996)
    New York : Wiley-Blackwell
    Biopolymers 38 (1996), S. 673-682 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Inclusion of Arg or Pro residues in proteins and peptides has been proved to play an essential role in biochemical functions through ionic interactions, conformational transitions, and formation of turns as well. In this study we present the conformational properties of the Ac-Arg-Ala-Pro (1), Ac-Arg-Ala-Pro-NH2 (2), Ac-Arg-Pro-Asp-NH2 (3), and Ac-Arg-Pro-Asp (4) tripeptides, using 1H-nmr spectroscopy and molecular dynamics. These peptides were modeled with the aim of studying the role of the Arg-guanidinium to carboxylate ionic interactions on the Xaa-Pro peptide bond isomerization. It was found with 1 and 4 that arginine preferentially interacts with the C-terminal carboxylate group, even though the β-carboxylate is also accessible. This tendency of the Arg moiety was found to induce the cis disposition of the Ala-Pro peptide bond in 1. It was also confirmed that the Arg…Asp side chain-side chain ionic interaction in 3 plays a key role in backbone folding and structural stabilization through a type I β-turn. The nmr pattern for 3 showed a remarkable similarity with that for various Arg-Tyr-Asp containing peptides, a sequence that is crucial for the adhesion properties of the Leishmania gp63 glycoprotein. © 1996 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 2
    Electronic Resource
    Electronic Resource
    Concept and design of a new class of sequential oligopeptide carriers (SOC) for covalent attachment of multiple antigenic peptides (1996)
    New York : Wiley-Blackwell
    Biopolymers 38 (1996), S. 291-294 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No abstract.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 3
    Electronic Resource
    Electronic Resource
    Conformational requirements for molecular recognition of acetylcholine receptor main immunogenic region (MIR) analogues by monoclonal anti-MIR antibody: A two-dimensional nuclear magnetic resonance and molecular dynamics approach (1993)
    New York : Wiley-Blackwell
    Biopolymers 33 (1993), S. 1123-1134 
    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 two [D-A70, A76] and [Aib70, A76] analogues of the α67-76 Torpedo acetylcholine receptor fragment, with low binding capacity for the anti main immunogenic region (MIR) antibodies, were studied in DMSO by two-dimensional nmr techniques and molecular dynamics simulations. The results were compared to the free and bound conformations of the [A76] analogue, which has twice more affinity for the anti-MIR monoclonal antibody 6 (mAb6), than the natural Torpedo sequence. It appeared that a single substitution of the A70, at a crucial position, by the D-A70 or Aib70, could modify completely the conformational behavior of the peptide and reduced its recognition by the anti-MIR antibody. The WNPADY rigid structure at the N-terminal part was essential for antibody recognition. The adjacent more flexible C-terminal sequence (GGIK) gives additional stability to the monoclonal antibody-peptide complex probably due to an adequate orientation of the peptide side chains in the complex, by setting them in close contact with the antibody. © 1993 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360330714
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  • 4
    Electronic Resource
    Electronic Resource
    Compared structures of the free nicotinic acetylcholine receptor main immunogenic region (MIR) decapeptide and the antibody-bound [A76] MIR analogue: A molecular dynamics simulation from two-dimensional NMR data (1996)
    New York : Wiley-Blackwell
    Biopolymers 40 (1996), S. 419-432 
    Details
    ISSN: 0006-3525
    Keywords: acetylcholine receptor ; myasthenia gravis ; antigen-antibody interaction ; anti-genic peptide ; two-dimensional nmr ; molecular dynamics ; DMSO solvent box ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Monoclonal antibodies against the main immunogenic region (MIR) of the muscle acetylcholine receptor (AChR) are capable of inducing experimental myasthenia gravis (MG) in animals. The epitope of these antibodies has been localized between residues 67 and 76 of the AChR α-subunit. The conformation in solution of the Torpedo californica MIR peptide and of its [A76] MIR analogue have been analyzed using molecular modeling based on nmr interproton distances and J-derived φ dihedral angles. Molecular dynamics simulations including dimethylsulfoxide as explicit solvent have been carried out on the free MIR peptide. Calculation of the structure of the [A76] MIR analogue bound to an anti-MIR monoclonal antibody have been performed in the presence of water molecules. A tightly folded structure appears for both peptides with a β-folded N-terminal N68-P-A-D71 sequence of type I in the free state and type III in the mAb6-bound state. The C-terminal sequence is folded in two different ways according to the result in the free and bound state of the peptides: two overlapping β / β or β / α turns result in a short helical sequence in the free MIR peptide, whereas the bound analogue is folded by an uncommon hydrogen bond closing an 11-membered cycle. This structural evolution is essentially the result of the reorientation of the hydrophobic side chains that are probably directly involved in peptide-antibody recognition. © 1997 John Wiley & Sons, Inc. Biopoly 40, 419-432, 1996
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    CD studies of synthetic polypeptides as histone models: Poly(L-Arg-L-Ile-Gly), poly(L-Arg-L-Nva-Gly), and poly(L-Arg-L-Nle-Gly) (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 213-229 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Sequential polypeptides (L-Arg-X-Gly)n were prepared as synthetic models of arginine-rich histones to study their structure and their stereospecific interactions with DNA. In our previous work the conformational characteristics of poly(L-Arg-L-Ala-Gly), poly(L-Arg-L-Val-Gly), and poly(L-Arg-L-Leu-Gly) have already been analyzed. To obtain further insight into the influence of the X residue side chain on the conformation of the (L-Arg-X-Gly)n polytripeptides, we now report their synthesis and cd properties when X represents the amino acid residues Ile, Nva, and Nle. The pentachlorophenyl active esters of the appropriate tripeptides were used to perform the polymerization, and the toluene-4-sulfonyl group was used to protect the arginine guanido group. CD spectroscopy showed that, in 100% trifluoroethanol, the degree of helical conformation increased in the order Ile → Nle → Nva. An equilibrium between β-turn, α-helix, and random-coil conformers occurred in 100% hexafluoroisopropyl alcohol, while a rise in the temperature or the addition of water favored the α-helix, the highest percentage of which was observed in a mixture of hexafluoroisopropyl alcohol: water (20 : 80) and in the order Ile → Nle → Nva. In aqueous solutions (at pH 7 and 12) the polymers behaved as a random coil, but they were forced to a less aperiodic structure, over a range of ionic strengths (0-0.5M NaF). A rise in temperature of up to 70°C in 100% trifluoroethanol resulted in a decrease of the α-helix percentage of the polymers, while in aqueous solutions the aperiodic structure decreased with increasing temperature. This study proved the importance of the nature of the X residue (length, Cβ branching) in relation to the structural order of the sequential polypeptides. We concluded that the polymers prepared are suitable models for arginine-rich histones.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360270205
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  • 6
    Electronic Resource
    Electronic Resource
    Two-Dimensional 1H-nmr study of antigen-antibody interactions: Binding of synthetic decapeptides to an anti-acetylcholine receptor monoclonal antibody (1991)
    New York : Wiley-Blackwell
    Biopolymers 31 (1991), S. 769-776 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two-dimensional NMR experiments [correlated spectroscopy (COSY) and two-dimensional transferred nuclear Overhauser enhancement spectroscopy (TR-NOESY)] have been applied to study the interactions of a monoclonal antibody (mAb) directed to the main immunogenic region (MIR) of the acetylcholine receptor (AChR), and four synthetic decapeptides from the MIR. The decapeptides were the Torpedo AChR α67-76 fragment (W 67-N68-P69-A70-D71-Y72-G73-G74-I75-K76) and its three [A69], [A73], and [A76] analogues. The results led to the following conclusions: (1) the magnitude of the TR-NOE cross peaks does not depend only on the structuration of the peptide in the bound state, but also on restrictions of the mobility, i.e., on the correlation time τc, which can be different for every residue; (2) the binding capacity of the synthetic peptides to mAbs measured by radioimmunoassay is directly correlated to the NOE magnitude; and (3) the combined interpretation of the COSY and TR-NOESY experiments gives a qualitative information about the nature and the overall conformation of the sequence which is in contact with the mAb binding site.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360310622
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