文摘
A matrix-assisted laser desorption/ionization (MALDI) iontrap mass spectrometer of new design is described. Theinstrument is based on a commercial Finnegan LCQ iontrap mass spectrometer to which we have added a MALDIion source that incorporates a sample stage constructedfrom a compact disk and a new ion transmission interface.The ion interface contains a quadrupole ion guide installed between the skimmer and the octapoles of theoriginal instrument configuration, allowing for operationin both MALDI and electrospray ionization modes. Theinstrument has femtomole sensitivity for peptides and iscapable of collecting a large number of MALDI MS andMALDI MS/MS spectra within a short period of time. TheMALDI source produces reproducible signals for 104-105 laser pulses, enabling us to collect MS/MS spectrafrom all the discernible singly charged ions detected in aMS peptide map. We describe the different modes of theinstrument operation and algorithms for data processingas applied to challenging protein identification problems.