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Molecular conformational analyses of dehydroalanine analogues
Author(s) -
Alemán Carlos,
Casanovas Jordi
Publication year - 1995
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.360360107
Subject(s) - dehydroalanine , chemistry , ab initio , energy minimization , tripeptide , crystallography , stereochemistry , helix (gastropod) , computational chemistry , peptide , organic chemistry , biochemistry , ecology , snail , biology
The conformational preferences of dehydroalanine (ΔAla) were examined through ab initio calculations. The geometries of the minimum energy conformations for N‐formyldehydro alanilamide and N‐acetyl‐N′‐methylamide of dehydroalanine were determined by gradient optimization at the HF/6‐31G* level, and correlation corrections were examined with MP2 single‐point energy calculations. Furthermore, HF/3‐21G ab initio geometry optimizations were performed on nine conformations of the model tripeptide N‐acetyl‐N′‐methylamide of didehydroalanine. The results indicate that the C 5 is the lowest energy conformation at all levels of theory. However, the relative energy of the helix conformation decreases when the number of ΔAla residues in the peptide chain increases. On the other hand, significant variations of the geometry upon conformational change were observed for the three compounds investigated. These results permit to extract important conformationally dependent geometry trends. The results of this study were compared to x‐ray diffraction data on single crystals of dehydroalanine‐containing peptides. © 1995 John Wiley & Sons, Inc.