Carbon 13 Nuclear Magnetic Resonance Spectroscopy of Myoglobins and Ribonuclease A Carboxymethylated with Enriched [2-13C]Bromoacetate

Cyanoferrimyoglobins of sperm whale and harbor seal, and bovine pancreatic ribonuclease A have been carboxymethylated with enriched [2-13C]bromoacetate. In each case the contribution of the enriched adduct was clearly discernible by 13C nuclear magnetic resonance. The new resonances appear as expected in the region of the α carbon atoms. In addition to the determination of chemical shifts the measurements were extended to determinations of T1 for the enriched resonances. The results on ribonuclease are particularly important in demonstrating that with available techniques the 13C nuclear magnetic resonance signal from even a single enriched carbon locus in a small protein can reveal information suitable for detailed interpretation.