12. An octapeptide composed of four repeating glycylalanyl units has:
(A) one free amino group on an alanyl residue.
(B) one free amino group on an alanyl residue and one free carboxyl group on a glycyl residue.
(C) one free amino group on a glycyl residue and one free carboxyl group on an alanyl residue.
(D) two free amino and two free carboxyl groups.
(E) two free carboxyl groups, both on glycyl residues.
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統計: 尚無統計資料
統計: 尚無統計資料