Carbon-13 Nuclear Magnetic Resonance Spectroscopy of Oxytocin, Related Oligopeptides, and Selected Analogs

The C-13 nuclear magnetic resonance (nmr) spectra of oxytocin and several analogs in dimethyl sulfoxide solution have been studied. Assignments of all 43 carbon resonances have been made by reference to the spectra of the linear precursors and through the use of partially deuterated peptides and oxytocin derivatives. The closing of the disulfide bond yielding oxytocin from the linear nonapeptide precursor results in a number of significant chemical shift changes, particularly of the α and β carbons, which cannot at present be interpreted in detail. Significant chemical shift differences are observed for some oxytocin analogs which may be related to conformational changes.