Femtosecond laser‐induced ionization/dissociation tandem mass spectrometry (fsLID‐MS/MS) of deprotonated phosphopeptide anions. (5th November 2013)

• Record Type: Journal Article
• Authors: Smith, Scott A.; Kalcic, Christine L.; Cui, Li; Reid, Gavin E.
• Is Part Of: Rapid communications in mass spectrometry. Volume 27:Number 24(2013)
• Page Start: 2807
• Page End: 2817
• Publication Date: 2013-11-05
• Subjects: Mass spectrometry -- Periodicals; 543.65
• DOI: 10.1002/rcm.6750
• Languages: English
• ISSNs: 0951-4198

Abstract

Abstract : RATIONALE: Radical‐directed dissociation techniques provide structural information which is complementary to that from conventional collision‐induced dissociation (CID). The analysis of phosphopeptide anions is warranted due to their relatively acidic character. As femtosecond laser‐induced ionization/dissociation tandem mass spectrometry (fsLID‐MS/MS) is uniquely initiated by field ionization, an investigation is warranted to determine whether fsLID may provide novel analytical utility for phosphopeptide anions. METHODS: Twenty‐three synthetic deprotonated phosphopeptide anions were introduced into a three‐dimensional quadrupole ion trap mass spectrometer via electrospray ionization. The ion trap was interfaced with a near‐IR (802 nm) ultrashort‐pulsed (35 fs FWHM) ultrahigh‐powered (peak power ~10 14 W/cm 2 ) laser system. Performance comparisons are made with other techniques applied to phosphopeptide anion analysis, including CID, electron detachment dissociation (EDD), negative electron transfer dissociation (NETD), activated electron photodetachment dissociation (activated‐EPD), and ultraviolet photodissociation (UVPD). RESULTS: FsLID‐MS/MS of multiply deprotonated phosphopeptide anions provides sequence information via phosphorylation‐intact a / x ions in addition to other sequence ions, satellite ions, and side‐chain losses. Novel fragmentation processes include selective c ‐ion formation N‐terminal to Ser/Thr and a phosphorylation‐specific correlation between xn –98 ion abundances and phosphorylation at the n th residue. Sequencing‐quality data required about 30 s of signal averaging. fsLID‐MS/MS of singly deprotonated phosphopeptides did not yield product anions with stable trajectories, despite significant depletion of the precursor. CONCLUSIONS: Multiply deprotonated phosphopeptide anions were sequenced via negative‐mode fsLID‐MS/MS, with phosphosite localization facilitated by a/x ion series in addition to diagnostic xn –98 ions. fsLID‐MS/MS is qualitatively competitive with other techniques. Further efficiency enhancements (e.g., implementation on a linear trap or/and higher pulse frequencies) may permit sequence analyses on chromatographic timescales. Copyright © 2013 John Wiley & Sons, Ltd.