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Local interactions in peptides. 1H-1H, 13C-H coupling constants and calculations for the conformational analysis of N-acetyl-N'-methylamides of aliphatic amino acids.

Authors
  • Fermandjian, S
  • Sakarellos, C
  • Aumelas, A
  • Toma, F
  • Gresh, N
Type
Published Article
Journal
International journal of peptide & protein research
Publisher
Wiley (Blackwell Publishing)
Publication Date
May 01, 1990
Volume
35
Issue
5
Pages
473–480
Identifiers
PMID: 2165470
Source
Medline
License
Unknown

Abstract

We report the results of a joint NMR and theoretical investigation devoted to the conformational properties of N-acetyl-N'-methylamides of aliphatic amino acids with side chains of increasing bulkiness: Gly, Ala, Leu, Ile, and tert.Leu. In this series, determination of the coupling constants 3JHNC alpha H together with the coupling constants 3JC'NC alpha H (thanks to specific carbon-13 labeling of the N-acetyl carbonyl group) led to the derivation of alternative A, B, and C parameters in a Karplus-type relation expressing the dependence of 3JC'NC alpha H upon the phi dihedral angle. The value of the latter is found to increase regularly following the increase of the side-chain bulkiness. The theoretical conformational analysis is performed by applying the SIBFA procedure, which uses empirical formulas based on ab initio SCF computations. The conformational energy maps illustrate the progressive distortion of the backbone conformation incurred in the series Gly to tert.Leu. Theoretical values computed for 3JHNC alpha H and 3JC'NC alpha H are found to be in a good quantitative agreement with the experimental ones.

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