The vasoactive intestinal peptide (VIP) prohormone has been characterized in the finch. (A) Aligned zebrafinch and chicken VIP prohormones show peptides (underlined) and prohormone cleaveages ("|" symbol) and highlight the few differences between these two species. (B) The VIP peptide HSDAVFTDNYSRF has been confirmed via tandem mass spectrometry. The peptide HSDAVFTDNYSRF was fragmented in the mass spectrometer. Two different fragment ion series (b- and y-ions) were obtained, depending on whether the charge was carried on the N-terminal or C-terminal side of the cleavage site. The amino acid residue(s) were assigned based on the mass difference between two peaks, as annotated by the blue and red letters. Based on this information, the sequence of this VIP-related peptide is unambiguously determined.