Abstract: A peptide is cleaved at various bonding sites into oligopeptides or similar fragments by digestion using proteinase K (S3). The obtained fragments are separated according to their kinds by reversed-phase chromatography and fractionated (S4), and each fragment is subjected to mass spectrometry to determine its mass (S6). For each peptide fragment, an amino-acid composition is calculated from the measured mass, and amino-acid sequence candidates are deduced from that composition. The amino-acid sequence candidates of the other peptide fragments are searched for a fragment having an overlapping portion available for combining two peptide fragments to obtain amino-acid sequence candidates of the original peptide (S7). The masses of the amino-acid sequence candidates are compared with a measured mass derived from a result of mass spectrometry of the original peptide to select a correct sequence (S6 and S8).

Abstract: Peptide-fragment mixtures obtained by fragmenting a sample with each of multiple enzymes which cause cleavage at different sites are subjected to mass spectrometry. De novo sequencing is performed on the obtained results to deduce partial sequence candidates for various kinds of fragments (S1 and S2). Using the fact that a specific amino acid residue should appear at the cleavage site depending on the enzyme, a partial sequence candidate including the terminal of the original amino acid sequence is extracted from a number of candidates (S6). The task of searching for and combining non-terminal partial sequence candidates including an overlapping portion is repeated (S7 and S8). The sequence candidates including the terminal are subsequently connected to the ends of the sequence obtained through the repetitive task (S9). The eventually obtained amino acid sequence is highly likely to be the correct solution (S10 and S11).

Abstract: When a terminal sequence to be investigated is specified (S1), a corresponding protein is extracted from a database containing known proteins linked with terminal sequences (S2). If one protein cannot be uniquely identified (“No” in S5), amino-acid residues to be bonded to the target terminal sequences are selected, and new terminal sequences with the selected amino-acid residues respectively added are created for further investigation (S7). Each new terminal sequence is examined as to whether or not one protein can be uniquely identified from it, and if not so, another amino-acid residue is added. While such processes are repeated, if it has been found that the protein can be uniquely identified before the sequence length reaches an upper limit, the sequence length is displayed (S9). If the sequence length has reached the upper limit without successful identification, a message saying that the protein cannot be identified is displayed (S11).

Abstract: A peptide is cleaved at various bonding sites into oligopeptides or similar fragments by digestion using proteinase K (S3). The obtained fragments are separated according to their kinds by reversed-phase chromatography and fractionated (S4), and each fragment is subjected to mass spectrometry to determine its mass (S6). For each peptide fragment, an amino-acid composition is calculated from the measured mass, and amino-acid sequence candidates are deduced from that composition. The amino-acid sequence candidates of the other peptide fragments are searched for a fragment having an overlapping portion available for combining two peptide fragments to obtain amino-acid sequence candidates of the original peptide (S7). The masses of the amino-acid sequence candidates are compared with a measured mass derived from a result of mass spectrometry of the original peptide to select a correct sequence (S6 and S8).