Tandem Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry of biomolecules surpasses other mass analysis techniques in mass resolution, mass accuracy, and complementary fragmentation techniques. Mass selective external ion accumulation is crucial for FT-ICR MS/MS, because ion accumulation and automated, data-dependent precursor ion selection occur rapidly and simultaneously. The recently developed electron capture dissociation (ECD) technique has attracted particular attention as a powerful method for identifying and localizing labile post-translational modifications in peptides and proteins. Infrared photons assist in dissociation of molecules that have captured an electron (McLafferty’s "activated ion" ECD), as well as providing an independent and complementary means of fragmentation. Millisecond timescale dissociation and efficient mass selective ion accumulation facilitate MS/MS on a timescale compatible with online separation methods (HPLC and CE). These techniques will be explained and applied to protein phosphorylation, glycosylation, and biomarker identification. FInally, hydrogen/deuterium exchange serves to map contact surfaces in protein complexes and enables "functional imaging" of biological motors.
Work supported by the NSF National High Field FT-ICR MS Facility (CHE-99-09502), Florida State University, and the National High Magnetic Field Laboratory in Tallahassee, FL.
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