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Use of natural‐abundance 15 N‐nmr spectroscopy to investigate the secondary structure of peptides: Gramicidin S
Author(s) -
Hawkes Geoffrey E.,
Randall Edward W.,
Hull William E.,
Convert Odile
Publication year - 1980
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.1980.360191010
Subject(s) - chemistry , solvent , gramicidin s , gramicidin , peptide , dimethyl sulfoxide , nuclear magnetic resonance spectroscopy , sulfoxide , chemical shift , solvent effects , hydrogen bond , crystallography , molecule , stereochemistry , organic chemistry , biochemistry , membrane
The natural‐abundance 15 N‐nuclear magnetic resonance (nmr) spectrum of the cyclic decapeptide gramicidin S has been measured and assigned in the solvents dimethyl sulfoxide, methanol, and 2,2,2‐trifluoroethanol. Three methods have been investigated to distinguish between peptide groups which are exposed to or shielded from the solvent. The solvent dependence of the 15 N chemical shift is correlated with the two types of peptide group in gramicidin Sthose with the carbonyl group exposed or shielded from the solvent. The second method monitors the lability of the N H proton (via the collapse of the reduced 15 N‐ 1 H coupling) in the presence of added base used to promote intermolecular exchange—peptide protons shielded from the solvent exchange more slowly. The third method looks at the temperature dependence of the 15 N chemical shifts in dimethyl sulfoxide. Here the data are not so distinctive as to allow the differentiation between solvent‐exposed or shielded NH bonds at all peptide groups.