Amino acid analysis of a dodecapeptide X produced the following mixture: 4Ala, 2Gln, 2Met, 2Phe & 2Ser.
N-Terminal analysis identified the sequence: Ser-Ala-Gln---. C-Terminal analysis identified: ---Ala-Phe. Selective peptide cleavage gave the following results.
Cyanogen bromide treatment generates three fragments:
A dipeptide, Ala-Phe.
A tetrapeptide (A) having a homoserine (Hsr) at the C-terminus.
A hexapeptide (B) having a homoserine (Hsr) at the C-terminus.
Chymotrypsin gave a single hexapeptide (C) and no other products.