Ionization rate and absolute intensity of peptides enhanced with matrix-assisted laser desorption/ionization in the presence of proteins

Human serum transferrin (HTF), bovine serum albumin (BSA), and horse spleen ferritin (HSF) have capacities of assisting the matrix to enhance ionization rate and absolute intensity both insulin(INS) and aplysia acidic peptide (AP) by laser desorption/ionization, and this enhancement can be up to 10 and 4 times, respectively. This phenomenon was independent on the concentration of INS, but dependent on these intensifiers strongly. Moreover, the similar enhancing rate of absolute intensity of INS was observed by both SZLF- and apoSZLF-assisted matrix, indicating that this effect was not relative to the 'metal ions of proteins, but their compositions and structures. The fragment numbers of HTF lysised with endopeptidease and matching rate with reference transferrin were greatly improved, in the presence of SZLF, - apoSZLF and HSF, when HTF was identified by a combined techniques, lysis enzyme I and peptide mass fingerprinting (PMF). This novel effect might play an important role in enhancing the reliability for identifying protein