Evaluation of various silicon-and boron-containing compounds for the detection of phosphorylation in peptides via gas-phase ion-molecule reactions.

Gas-phase ion-molecule reactions [IMR] of various boron- and silicon-containing neutrals were investigated as a potential route for detecting phosphorylation within peptides in the negative ion mode. Trimethyl borate (TMB), triethyl borate (TEB) and N,O- Bis(trimethylsilyl)acetamide (TMSA), unlike diethylmethoxyborane (DEMB), diisopropoxymethylborane [DiPMB] and chlorotrimethylsi- Lane (TMSCIL], reacted differently if a phosphate moiety was present and thus are suitable to detect phosphorylation. During multistage collision-induced dissociation experiments of the reaction products of IMR with TMB and TEB, the [LSsF - 4H + B]- ion formed a modified y2 fragment allowing the phosphorylation site to be assigned, unlike reaction products of DEMB and DiPMB which lost both the phos- phoric acid and the boron-containing moiety.