This paper reports the detection of all the proton magnetic resonances from the aromatic rings of the three tyrosine residues of hen egg white lysozyme. Procedures, including spin decoupling, for the full assignment of these residues are described. To explain the appearance and behaviour of these resonances it is postulated that the tyrosine rings are able to flip between equivalent conformations at rates exceeding 10
4
s
-1
.
Nuclear magnetic resonance studies of the structure and binding sites of enzymes. II. Spectral assignments and inhibitor binding in hen egg-white lysozyme.