Following combinations are possible for tetrapeptide Val —Phe —Gly—Ala Val —Gly—Phe —Ala Phe — Gly — Val — Ala Phe —Val —Gly—Ala 1. In all above sequences C-terminal is alanine 2. Glycine is optically inactive amino acid, hence It should not be N-terminal so, only above combination are possible.