Carbon-13 magnetic resonance evaluation of polypeptide secondary structure and correlation with proton magnetic resonance studies.

With the use of appropriately chosen solvent pairs it is demonstrated that solvent dependence of peptide carbonyl carbon resonances can be correlated with polypeptide secondary structure. Solvent titrations show the peptide carbonyl which is intramolecularly hydrogen bonded to exhibit less chemical shift on going from a dimethylsulfoxide solution to a solution containing a solvent which is a good proton (or deuteron) donor. Effective solvent systems are dimethylsulfoxide paired with water, trifluoroethanol, or methanol. This approach is demonstrated with the pentapeptide of elastin.