Patent ID: 7384790

Claim:
A method for analyzing the C-terminal amino acid sequence of a peptide to be examined, which method comprises steps of: releasing the C-terminal amino acids in sequence from the peptide to be examined by chemical means to prepare a mixture containing a series of reaction products thereof, subjecting the series of reaction products and the original peptide to mass spectrometry to measure the decreases in molecular weight associated with the successive release of the C-terminal amino acid thereof, and identifying a series of the amino acids removed successively, based on a series of the decrease in the molecular weight measured and arranging the amino acids identified from the C-terminal to obtain the information of the C-terminal amino acid sequence of the peptide, wherein the technique of treatment used in the step of releasing the C-terminal amino acids is a means comprising steps of: allowing an alkanoic acid anhydride and a perfluoroalkanoic acid both of vapor phase, which are supplied from a mixture containing an alkanoic acid anhydride with a small amount of a perfluoroalkanoic acid added thereto, to act on a dry sample of the peptide to be examined in a dry atmosphere at a temperature selected in a range of 15 to 60° C.; and carrying out the release of the C-terminal amino acid in association with the process that at the C-terminal of the peptide, the formation of a 5-oxazolone structure represented by the following general formula (III): wherein R1 is a side chain of the C-terminal amino acid of the peptide, and R2 is a side chain of the amino acid residue positioned just before the C-terminal amino acid, is followed by the cleavage of the 5-oxazolone ring.