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Ab‐initio molecular orbital study of the cis/trans conformations of the peptide bond
Author(s) -
Ramani R.,
Boyd Russell J.
Publication year - 1981
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.560200710
Subject(s) - ab initio , chemistry , molecular orbital , globular protein , peptide , computational chemistry , protonation , peptide bond , crystallography , fragment molecular orbital , ab initio quantum chemistry methods , force field (fiction) , molecule , physics , organic chemistry , quantum mechanics , ion , biochemistry
Ab‐initio molecular orbital (MO) calculations on the model peptide, N ‐methylacetamide (NMA), protonated N ‐methylacetamide (p‐NMA), and two natural dipeptides, glyclyglycine (Gly‐Gly) and alanylalanine (Ala‐Ala), are reported. Calculations at the STO‐3G. 3‐21G. and 4–31 G levels account for the predominance of the trans conformation in globular proteins. By use of p‐NMA as a model precursor, the formation of the peptide bond is studied by the methods of molecular quantum mechanics. These calculations lead to the conclusion that the trans conformation should predominate, in agreement with the crystal structural data on globular proteins. In order to reduce the amount of computer time required for what are evidently the first ab‐initio MO calculations on natural dipeptides, force‐field calculations have been employed to obtain the conformational potential energy maps.