[Identification of protein spots in silver-stained two-dimensional gels based on chemically assisted fragmentation by MALDI-TOF-PSD mass spectrometry].

Guanidination of the epsilon-amino group of lysine-terminated tryptic peptides,accomplished with O-methylisourea hydrogen sulfate, converted lysine into homoarginine residues, improving detection in MALDI-MS. Then tryptic peptides were labeled with sulfonic acid groups at the N-termini using 3-sulfopropionic acid NHS-ester chemistry. The derivatives enhanced post-source decay (PSD) fragmentation signals and produced a spectrum containing only y-ions. This facilitated de novo peptide sequencing, so it is an important contribution to unambiguous protein identification in proteome research. This method was successfully applied in nasopharyngeal carcinoma(NPC) proteome study.