An investigation of contributions to carbon‐13 spin‐lattice relaxtion in amino acids and peptide hormones

Carbon‐13 spin‐lattice relaxation times have been measured in glycine and the tripeptide pro‐leu‐gly‐NH₂. These times are compared with those measured in the same compounds where the glycine α‐carbon has been deuterated. In this manner evidence is obtained which indicates that mechanisms other than dipolar interactions with covalently bonded protons may contribute to carbon‐13 spin‐lattice relaxation. The effect of these additional mechanisms is found to be non‐negligible for the carbonyl carbon of glycine and the glycine α‐carbon of the tripeptide. The implication of these findings for deducing motional information from carbon‐13 relaxation measurements is briefly discussed.