Nano-electrospray and microbore liquid chromatography-ion trap mass spectrometry studies of copper complexation with MHC restricted peptides

The formation of copper/peptide complex ions by nano-electrospray and micro bore HPLC-electrospray mass spectrometry has been investigated for major hi stocompatibility complex (MHC) class I and class II restricted peptides. Po st-column addition of copper(II) acetate following microbore HPLC-MS separa tion was carried out using a mixing T-piece or via the sheath flow inlet of the electrospray source. Optimal analytical conditions for copper complex ion formation were determined by variation of copper concentration, pH, neb ulization gas supply and spray voltage. Tandem mass spectrometry of copper/ peptide complex ions provides peptide sequence information and insight into the peptide chelation sites. Copper associated y fragment ions dominate th e product ion spectrum for non-histidine containing peptides, but both b an d y copper complex ions were observed for the histidine containing MHC clas s I associated peptide gp70.