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Nuclear magnetic resonance and conformational energy calculations of repeat peptides of tropoelastin: Correlation of 1 J( 15 N‐ 1 H) with nonplanarity of peptide moiety
Author(s) -
Renugopalakrishnan V.,
Khaled A.,
Okamoto K.,
Urry D. W.
Publication year - 2009
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.560120711
Subject(s) - planarity testing , chemistry , moiety , dipeptide , tripeptide , cndo/2 , ring (chemistry) , peptide , stereochemistry , hydrogen bond , crystallography , proton nmr , chemical shift , computational chemistry , molecule , organic chemistry , biochemistry
Conformational energy calculations and 1 H and 13 C nuclear magnetic resonance (NMR) studies in CDCI 3 of a tripeptide, N ‐Ac‐Gly 1 ‐L‐Val 2 ‐Gly 3 ‐OMe, suggested the occurrence of an II‐membered hydrogen‐bonded ring, or γ‐turn conformation. The theoretical calculations indicated that the conformation occurs when there is a distortion of the planarity of the peptide moiety. An 15 N NMR study of the tripeptide in CDCI 3 was undertaken to see if these spectral parameters might correlate with deviations from planarity. 1 H, 13 C, and 15 N NMR studies were also carried out on the dipeptide N ‐Ac‐L‐Val 1 ‐Gly 2 ‐OMe, which argue for the occurrence of an 8‐membered hydrogen‐bonded ring, or C 8 conformation and even greater distortions from peptide planarity. Therefore a theoretical investigation of this problem, using both the empirical and molecular orbital calculations in the CNDO/2 approximation, was undertaken, the results of which indicate large distortions of the planarity of the peptide moiety. While further work is required before the detailed functional dependence of NMR parameters to planarity of the peptide moiety can be established, a systematic variation of the 1 J ( 15 N‐ 1 H) coupling constant with peptide planarity is observed for the molecules discussed.