On the tyrosine residues of ribonuclease A

The six 13Czeta resonances of the 6 tyrosine residues of ribonuclease A have been resolved by high field 13C Fourier transform nuclear magnetic resonance spect=oscopy. Titration studies of these resonances reveal 1 nontitrating or buried tyrosine residue, 1 partially buried residue, and 4 normally titrating residues, which are tentatively identified.