1P-01 PDF
Mechanism of y-ion formation in MALDI-ISD of peptides
It has been known that neutral fragments c, z’ and z-matrix are generated by the cleavage at N-Cα bond of the backbone of peptides and proteins, which occurs immediately after hydrogen addition in the ion-source of MALDI-TOFMS. This is called in-source decay (ISD). Whether c, z’ and z-matrix can be observed or not as ion peaks, it depends on the acidity or basicity of constituting amino acids. When a peptide ACTH18-39 is used as an analyte, generally, c-series and z’/ y/ z-ANL ions were observed in positive-ion and in negative-ion, respectively. When AgCl was added as an additive, preferential y-series ions were observed in parts of the matrix/analyte crystal in negative-ion mode. Here we examined the mechanism for the formation of y-series ions on the basis of the reaction mechanism and kinetics for MALDI-ISD.