Carbon 13 Nuclear Magnetic Resonance of Peptides in the Amino-terminal Sequence of Sperm Whale Myoglobin

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.