The amino acid sequence of the cyanogen bromide (CNBr) fragment CB I from the Ala chain of ricin D, the largest of three CNBr fragments, was established by manual Edman degradation of the peptides obtained by tryptic, chymotryptic or peptic digestion of fragment CBI. The total number of amino acid residues of fragment CB I accounted for 140 (54%) out of 260 residues in the Ala chain of ricin D.
