we were thus directed to the conclusion that angiotonin contains ( 1 ) a free terminal amino group , ( 2 ) a free terminal carboxyl group , ( 3 ) one basic amino acid residue which may be terminal but its carboxyl must be united in a peptide linkage , ( 4 ) one central dibasic amino acid residue in combination with an aromatic amino acid residue , ( 5 ) an aromatic amino acid residue which may be part of ( 4 ) and , if not part of ( 4 ) must be terminal with its carboxyl group in peptide linkage .
C0301714
basic amino acid
C0002520
amino acid