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In mass spectrometry, de novo peptide sequencing is the method in which a peptide amino acid sequence is determined from tandem mass spectrometry. Knowing the amino acid sequence of peptides from a protein digest is essential to study the biological function of the protein. In the old days, this was accomplished by the Edman degradation procedure. Today, analysis by a tandem mass spectrometer is a more common method to solve the sequencing of peptides. Generally, there are two approaches: database search and de novo sequencing. Database search is a simple version as the mass spectra data of the unknown peptide is submitted and run to find a match with a known peptide sequence, the peptide with the highest matching score will be selected. This approach fails to recognize novel peptides since it can only match to exited sequences in the database. De novo sequencing is an assignment of fragment ions from a mass spectrum. Different algorithms are used for interpretation and most instruments come with de novo sequencing programs. ==Peptide fragmentation== Peptides are protonated in positive-ion mode. The proton initially locates at the N-terminus or a basic residue side chain, but because of the internal solvation, it can move along the backbone breaking at different sites which result in different fragments. The fragmentation rules are well explained by some publications.〔〔doi:10.1002/0470118490〕 Three different types of backbone bones can be broken to form peptide fragments: alkyl carbonyl (CHR-CO), peptide amide bond (CO-NH), and amino alkyl bond (NH-CHR). 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「De novo peptide sequencing」の詳細全文を読む スポンサード リンク
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