A tandem quadrupole/time-of-flight mass spectrometer with a matrix-assisted laser desorption/ionization source: design and performance

A matrix-assisted laser desorption/ionization (MALDI) source has been coupl ed to a tandem quadrupole/time-of-flight (QqTOF) mass spectrometer by means of a collisional damping interface. Mass resolving power of about 10,000 ( FWHM) and accuracy in the range of 10 ppm are observed in both single-MS mo de and MS/MS mode. Sub-femtomole sensitivity is obtained in single-MS mode, and a few femtomoles in MS/MS mode, Both peptide mass mapping and collisio n-induced dissociation (CID) analysis of tryptic peptides can be performed from the same MALDI target. Rapid spectral acquisition (a few seconds per s pectrum) can be achieved in both modes, so high throughput protein identifi cation is possible, Some information about fragmentation patterns was obtained from a study of the CID spectra of singly charged peptides from a tryptic digest of E. coli citrate synthase, Reasonably successful automatic sequence prediction (>90 %) is possible from the CID spectra of singly charged peptides using the SC IEX Predict Sequence routine, Ion production at pressures near 1 Torr (rath er than in vacuum) is found to give reduced metastable fragmentation, parti cularly for higher mass molecular ions. Copyright (C) 2000 John Wiley & Son s, Ltd.