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Conformational analysis of polyoxyethylene‐bound homo‐oligo‐ L ‐glutamates in a weakly interacting medium, CDCl 3
Author(s) -
Ribeiro Anthony A.,
Saltman Robert,
Goodman Murray
Publication year - 1985
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.360241219
Subject(s) - chemistry , chemical shift , hydrogen bond , solubility , residue (chemistry) , solvent , nuclear magnetic resonance spectroscopy , crystallography , proton nmr , deuterium , stereochemistry , molecule , organic chemistry , physics , quantum mechanics
Abstract A detailed conformational analysis of polyoxyethylene‐bound N‐ t ‐butyloxycarbonyl homo‐oligo‐ L ‐glutamates up to the heptamer was carried out in CDCl 3 solution using high‐resolution 1 H‐nmr spectroscopy. Unequivocal assignments of resolved backbone NH and α‐CH resonances were obtained with specifically deuterated oligomers. From nmr measurements, chemical‐shift dependencies with respect to temperature and solvent, and the line‐broadening effects of free radicals allowed the determination of hydrogen‐bonded residues. The nmr data, along with model‐building studies, suggest that seven‐membered rings may exist in the N‐terminal portion of these peptides. Replacement of the N‐ t ‐butyloxycarbonyl group by an acetyl or pyroglutamyl residue gave aggregated peptides, pointing to a special contribution by the Boc group to hydrogen bonding and solubility in CDCl 3 .