Reductive glutaraldehydation of amine groups for identification of protein N-termini

In the present work, reductive alkylation of proteins and peptides with glutaraldehyde (reductive glutaraldehydation) is reported. The reaction is highly efficient and forms piperidine at the N-terminus as well as the side chain of lysine residues. The complete modification of protein amines was achieved by reductive glutaraldehydation in solution or in the gel in less than 15 min. The glutaraldehyde-modified peptides display an enhanced intensity in mass spectra and show higher retention time in reversed phase chromatography in comparison to unmodified peptides. Fragmentation of glutaraldehyde-modified proteins and peptides generates a1 fragment ions with enhanced intensity in MS/MS spectra. Thus, a method based on reductive glutaraldehydation and LC-MS/MS analysis has been developed to determine the N-terminal residue of proteins with free N-termini.