Patent ID: 8501488

Claim:
A method for sequencing and quantifying amino acids in a sample of polypeptides, comprising: dividing the sample of polypeptides into a first polypeptide sample and a second polypeptide sample; separately degrading each of the first polypeptide sample and the second polypeptide sample using proteolytic enzymes to form a first degraded oligo peptide mixture and a second degraded oligo peptide mixture, wherein the C-terminus of each degraded oligo peptide of the first and second oligo peptide mixtures is arginine or lysine; derivatizing the first degraded oligo peptide mixture having arginine or lysine at the C-terminus with a compound for N-terminal substitution containing 12 C, and derivatizing the second degraded oligo peptide mixture with a compound for N-terminal substitution containing 13 C, wherein the compound for N-terminal substitution containing 12 C is a compound represented by Formula 3, and the compound for N-terminal substitution containing 13 C is an isotope of the compound for N-terminal substitution containing 12 C, in which each 12 C of the phenyl ring in the compound of Formula 3 is replaced by 13 C; mixing the first derivatized oligo peptide mixture and the second derivatized oligo peptide mixture to form a third mixture; separating the third mixture with Reverse-Phase Liquid Chromatography to form a separated third mixture; obtaining a base peak chromatogram and MS/MS spectra of the separated third mixture using a mass spectrometer; and interpreting the obtained spectral results of the separated third mixture.