自我介紹
An oligopeptide or (simply) a peptide is a polypeptide less than 30-50 amino acids long. A dipeptide has two amino acids. A tripeptide has three amino acids. A pentapeptide has five amino acids. A nonapeptide has nine amino acids (e.g., oxytocin). A neuropeptide is a peptide that is active in association with neural tissue.