Abstract
Abstract The natural abundance carbon 13 nuclear magnetic resonance spectra of the peptides l-valyl-l-leucyl-l-seryl-l-glutamylglycine, comprising the first 5 residues of the amino terminus of sperm whale myoglobin, l-leucyl-l-seryl-l-glutamic acid, and l-seryl-l-glutamylglycine have been recorded by continuous wave and pulsed Fourier transform techniques. Signal assignments were made by comparison of the peptides with each other and with the free amino acids, by the pH dependence of the chemical shifts, and by modification of the degree of proton decoupling in certain cases. The chemical shift dependence of specific carbon centers on their position in the oligopeptide sequences and the influence of the state of ionization of various groups on neighboring carbon sites were explored.
Highlights
The chemical shift dependence of specific carbon centers on their position in the oligopeptide sequences and the influence of the state of ionization of various groups on neighboring carbon sites were explored
Materials-The pentapeptide, L-valyl-L-leucyl-n-seryl-n-glutamylglycine (Cycle Chemical Corporation) was the same sample previously studied in this laboratory (l&12)
The t-BOC-glutamic acid y-benzyl ester was prepared from the glutamic acid y-benzyl ester (Mann) in dimethyl sulfoxide (Reference 14, p. 30)
Summary
Materials-The pentapeptide, L-valyl-L-leucyl-n-seryl-n-glutamylglycine (Cycle Chemical Corporation) was the same sample previously studied in this laboratory (l&12).The tripeptides, L-leucyl-n-seryl-L-glutamic acid and n-seryl-L-glutamylglycine, were synthesized by the Merrifield solid phase procedure [13] according to the steps outlined by Stewart andYoung [14]. Materials-The pentapeptide, L-valyl-L-leucyl-n-seryl-n-glutamylglycine (Cycle Chemical Corporation) was the same sample previously studied in this laboratory (l&12). L-glutamylglycine, were synthesized by the Merrifield solid phase procedure [13] according to the steps outlined by Stewart and. The t-BOCi-glycine and t-BOC-leucine were prepared by the method of Schnabel [15]. The t-BOC-glutamic acid y-benzyl ester was prepared from the glutamic acid y-benzyl ester (Mann) in dimethyl sulfoxide Thin layer chromatography on Corning porous glass plates in chloroformacetic acid, 19: 1 by volume, showed it to be homogeneous (RI = 0.48). The t-BOC-serine-0-benzyl ether (Sigma) was used without further purification
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