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Infrared spectroscopic study of C 7 intramolecular hydrogen bonds in peptides
Author(s) -
Rao Ch. Pulla,
Balaram P.,
Rao C. N. R.
Publication year - 1983
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.360220908
Subject(s) - intramolecular force , intermolecular force , chemistry , hydrogen bond , chloroform , crystallography , hydrogen , low barrier hydrogen bond , infrared spectroscopy , photochemistry , molecule , stereochemistry , organic chemistry
The ir‐spectra in the NH stretching region of Piv‐Pro‐NHMe and Boc‐Pro‐NHMe have been studied in carbon tetrachloride and chloroform solutions over a wide range of concentrations. Based on the concentration dependence of the NH stretching bands, it has been shown that the characteristic NH stretching band due to the C 7 intramolecular hydrogen bond is around 3335 cm −1 . Intermolecular hydrogen bonding also occurs to a small extent in these peptides, giving rise to a slight concentration dependence of the NH stretching bands. The band around 3335 cm −1 need not necessarily be due to C 7 hydrogen bonds alone as proposed by Tsuboi et al. or to intermolecular hydrogen bonding alone as proposed by Maxfield et al.; this conclusion is supported by studies on Boc‐Leu‐NHMe, which undergoes only intermolecular hydrogen bonding. We have shown that Z‐Aib‐Aib‐OMe and Z‐Aib‐Ala‐OMe form C 7 intramolecular hydrogen bonds in addition to C 5 intramolecular hydrogen bonds. The present studies also show that all the peptides studied exist in more than one conformation in solution.