| Abstract: | We report here a method for the identification of free N-terminal peptide of in gel digested isolated proteins. It is based in the difference between the isotopic ion distribution of N-terminal peptide and internal peptides. After guanidination of lysine residues, the primary amino groups of the gel-entrapped protein are blocked with an equimolar mixture of normal and deuterated acetic anhydride. Upon MS analysis internal peptides display a normal isotopic ion distribution while the N-terminal peptide shows a complex isotopic ion distribution. |
