A Control System for a Four-Sector Tandem Mass Spectrometer

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We have developed a new acquisition processor unit simultaneously to control MS1 and MS2 of a four-sector tandem mass spectrometer that makes it possible to acquire the MS/MS spectra from multi-precursor ions in a single measurement. The difficulty in operation of the present four-sector tandem mass spectrometer (MS1 needs to be manually switched mass to mass to the center of each precursor ion, resulting in time and sample loss) can be overcome by connecting it to the above control system.In the present system, to switch the magnetic field to the precise center of the precursor ions in a MS1, it can be correctly compensated by re-calibration using an appropriate calibrant interpolating each selected mass. Each precursor ion automatically selected in the MS1 can be decomposed independently by bombardment with helium in a collision cell, and resultant fragment ions derived from each precursor ion can be readily analyzed in a MS2. In this process, four sets of digital analo, converters (DAC) controlling magnetic and electric fields of both MSI and MS2 can be syiicliroiiized by system engineering work station (a data acquisition system in JMS-HX221CP, Institute for Protein Research).A four-sector tandem mass spectrometer (JMS-HX221CP) equipped with the above MS/MS control system was used for analyzing, primary structures of peptides and proteins. The CPUcontrolled MS/MS of multi-precursor ions was found to be effective and rapid in peptide and protein sequencing. F Urthermore, a combined use of a stable-isotope labeling, method of peptides and the present tandem mass spectrometer allowed easily and reliably to determine amino acid sequences of peptides and proteins.