After modification of the active tryptophan residue of lysozyme with NBS, chymotryptic peptides were isolated by phosphocellulose column chromatography and tryptic peptides by Sephadex G-25 column chromatography following the characteristic absorption spectrum of the modified tryptophan residue.
The amino acid compositions of peptides containing modified tryptophan residue were analyzed quantitatively. Pure peptides con-taining tryptophans 62 and 63 were obtained from both hydrolyzates. Edman degradation of tryptic peptide, T-2, showed that the modified tryptophan, and hence the active tryptophan, is in the 62 nd position in the .amino acid sequence of lysozyme.