B. J. Dale, D. Jones
1977
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Journal
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy
Abstract
Abstract 100 and 220 MHz 1 H NMR spectra have been measured in pyridine- d 5 and in chloroform- d 1 / trifluoracetic-acid solution for a blocked dipeptide, Z -Cys(Bzl)-Asn (I), and a blocked tripeptide, Z -Val-Cys(Bzl)-Gly-OMe (II) involved in insulin synthesis. Fractional side-chain rotamer populations, extracted from the C x H C β H 2 coupling constants by the Pachler procedure, are a / b = 0.23/0.29 and c (three hydrogens gauche ) = 0.48 for Asn rotation in I, and a / b = 0.47/0.32 and c = 0.21 for Cys rotation in II. Variations of population with temperature are also reported from 220 MHz spectra of L -asparagine in acid D 2 O solution.