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Studies of peptide conformation: Backbone folding of tetrapeptide derivatives in methanol and water
Author(s) -
Kopple Kenneth D.,
Go Anita
Publication year - 1976
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.1976.360150908
Subject(s) - chemistry , tetrapeptide , folding (dsp implementation) , peptide , methanol , proton , solvent , stereochemistry , crystallography , organic chemistry , biochemistry , physics , quantum mechanics , electrical engineering , engineering
Derivatives of tetrapeptide sequences considered likely to form β‐turns were investigated by the study of their proton magnetic resonances in methanol and in water. Differential broadening of N—H resonances by an added nitroxyl was used to indicate the presence of the sequestered N—H proton expected in β‐turn conformations. Transfer of magnetic saturation from solvent water protons to N—H protons was also examined. The evidence is consistent with significant contributions by β‐turn‐like backbones to the conformational averages in methanol of the sequences Gly‐ L ‐Pro‐ D ‐Val‐Gly, D (or L )‐Val‐ L ‐Pro‐Gly‐Gly, and Gly‐ L ‐Pro‐ L ‐Asn‐Gly, but not the sequence Gly‐ D ‐Ala‐ L ‐Val‐Gly. It is suggested that a Type I turn, Likely in Gly‐ L ‐Pro‐ L ‐Asn‐Gly derivatives, is characterized by sequestered N—H protons of both the third and fourth residues. For all of the peptide derivatives, save possibly Ac‐ L ‐Val‐ L ‐Pro‐Gly‐Gly‐NHNH 2 , contributions from folded structures in water are not detectable by line‐broadening experiments. However, the transfer of saturation experiments may be interpreted as indicating some degree of chain folding in water.