MS Analysis Expert

The sequence of a protein molecule is the basis for the function of a protein. Accurate determinat ion of protein sequence plays an important role in the study of protein functional epitopes, detection of commercial monoclonal antibodies, vaccines, and kits. Although there are many studies on protein sequencing, accurate sequencing of proteins is still not as fast and accurate as that of DNA. Protein sequencing is mainly hampered by the purification of protein samples, and the complexity of factors that make up the amino acid com position of proteins. De novo   protein sequencing  is  also called novel protein sequencing. This technique deduces t he amino acid sequence based on the difference in mass between a series of regular fragment ions generated by the peptide collision with an inert gas. We can guess the amino acid sequence and post-translational modifications based on the y ion and b ion at the cleavage of the peptide bond. De novo  sequencing has a uniq...

I ’ ve  mentioned in   The Principle of Protein De Novo Sequencing   that the theoretical basis for de novo  sequencing  analysis of proteins is based on the fact that the peptides are regularly broken when fragmentation is induced by MS/MS. According to the position of the peptide fragment, different types of ions can be generated. The ions produced near the N-terminus are a, b, and c types of ions, and the ions generated near the C-terminus are x, y, and z. Take the N terminal  cleavage ion as an example, the a-type ion is the N-terminal ion   generated by the cleavage of the C - C bond in front of the first amino acid  C=O, t he b-type ion is the N-terminal iongenerated by the cleavage of the C-N bond between the first amino acid and the second amino acid ,  and the c-type ion is formed by the cleavage of the N - C bond of the second amino acid (as shown in Figure 1 ).   For N-terminally cleaved ions, the different positions of t...