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Co‐oligopeptides containing two aromatic residues spaced by glycyl residues. X. Proton magnetic resonance study of co‐oligopeptides of tryptophan and glycine
Author(s) -
Skrabal Peter,
Rizzo Vincenzo,
Baici Antonio,
Bangerter Felix,
Luisi Pier Luigi
Publication year - 1979
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.1979.360180417
Subject(s) - chemistry , tripeptide , tryptophan , stereochemistry , oligopeptide , steric effects , side chain , conformational isomerism , peptide , resonance (particle physics) , residue (chemistry) , crystallography , molecule , amino acid , organic chemistry , biochemistry , physics , particle physics , polymer
The 1 H‐nmr spectra of co‐oligopeptides of tryptophan and glycine with structure H‐Gly‐Trp‐(Gly) n ‐Trp‐Gly‐OH ( n = 0–2) and those of several di‐ and tripeptides have been recorded at 360 MHz with CD 3 OD solutions containing 0.1 N NaOD. The assignment of resonance signals was generally possible by comparing the spectra of structurally related peptides with each other. In order to solve the remaining ambiguities in the assignment, H‐(αL,βS)(α,β‐ d 2 )Trp‐OH, H‐Trp‐(αL,βS)(α,β‐ d 2 )Trp‐OH, and H‐Trp‐(δ 1 ,ε 2 ,ζ 2 ,ζ 3 ,η 2 ‐ d 5 )Trp‐OH have been prepared and their spectra compared with those of the undeuterated compounds. The distribution of rotamers around the χ 1 and (in two cases) χ 2 torsion angles of the side chains has been obtained from the vicinal coupling constants 3 J H α H βand from the long‐range coupling constants 4 J H β H δ1. These data and an analysis of the chemical shifts of the Gly‐C α protons suggest that the orientation of the aromatic side chain is influenced by the following order of decreasing interaction with the functional groups at N‐ and C‐side: ‐NH 2 > –NHCO– > –CONH–> –COO − . This rule does not hold for the second Trp residue of di‐ and tripeptides containing the ‐Trp‐Trp‐ sequence, which has tentatively been attributed to steric effects.