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Conformational Preferences in Small Peptide Models: The Relevance of cis / trans ‐Conformations
Author(s) -
Jangra Harish,
Haindl Michael H.,
Achrainer Florian,
Hioe Johnny,
Gschwind Ruth M.,
Zipse Hendrik
Publication year - 2016
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201601828
Subject(s) - conformational isomerism , dipeptide , chemistry , solvation , amide , peptide , protein folding , crystallography , stereochemistry , computational chemistry , molecule , organic chemistry , biochemistry
The accurate description of cis / trans peptide structures is of fundamental relevance for the field of protein modeling and protein structure determination. A comprehensive conformational analysis of dipeptide model Ace‐Gly‐NMe ( 1 ) has been carried out by using a combination of theoretical calculations and experimental ( 1 H and 13 C NMR and NOESY) spectroscopic measurements to assess the relevance of cis ‐peptide conformers. NMR measurements in dimethyl sulfoxide (DMSO) solution and calculations employing a continuum solvation model both point to the extended trans , trans conformer C5_tt as the global minimum. The cis ‐peptide structures C5_ct and C5_tc , with the N‐ or C‐terminal amide group in cis ‐conformation, are observed separately and located 13.0±2 kJ mol −1 higher in energy. This is in close agreement with the theoretical prediction of around 12 kJ mol −1 in DMSO. The ability of common protein force fields to reproduce the energies of the cis ‐amide conformers C5_ct and C5_tc in 1 is limited, making these methods unsuitable for the description of cis ‐peptide structures in protein simulations.