Preliminary comparison of precursor scans and liquid chromatography-tandemmass spectrometry on a hybrid quadrupole time-of-flight mass spectrometer

Recent mass spectrometry instrumentation developments include the appearanc e of novel hybrid tandem instrumentation, Q-TOF, consisting of a quadrupole mass analyzer (MS1) and a time-of-flight (TOF) analyzer. The TOF analyzer is not scanned, but collects all fragment ions entering the analyzer at a g iven time. Thus, the typical precursor scan experiment cannot be performed. Instead, a full MS-MS spectrum can be acquired for each mass passed by MS1 . Appropriate data manipulation, i.e. extracted ion current chromatograms, can correlate specific fragment ion formation to the parent ion. Precursor scanning and LC-MS-MS are compared on a Q-TOF instrument for the determinat ion of protein modifications, including acetylation and phosphorylation. Mo del peptides used for phosphopeptide detection were generated from a mixtur e of p-casein. Model acetylated peptides were generated from a mixture of a cetylated substance P1-9 and substance P1-11. The results were then applied to a more complex mixture, a digest of HIV-p24. Results indicate that prec ursor scanning is useful for screening, but that LC-MS-MS has a sensitivity advantage and is less susceptible to suppression effects. LC-MS-MS, theref ore, appears to be better for the detection of trace components in complex mixtures. (C) 1999 Elsevier Science BN. All rights reserved.