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Electrospray ionization (ESI) is a very gentle form of ionization, which enables the intact transfer into the gas phase and detection of large multi-protein structures with little or no fragmentation; when ESI is coupled to mass spectrometry, non-covalently assembled macromolecular protein complexes can be detected and accurately mass measured.
The transfer of non-covalently associated protein-protein complexes from solution to the gas phase generally results in the formation of ions possessing relatively few charges; the m/z values are often above 10,000. In some of the data presented in this poster, MS/MS activation of such biomolecular complexes can produce ions with m/z values in excess of 20,000.
By coupling an ion mobility separator (IMS) with a time-of-flight (ToF) mass spectrometer, one can not only accurately mass measure intact biomolecular complexes, but also one can measure their collisional cross-sections and differences in cross-section produced upon activation, and detect subtle conformation differences, which are not evident from spectral data alone.
Here, we show the analysis of several different, non-covalently associated protein-protein complexes, which differ vastly in mass and collisional cross-section, by IMS-ToF-MS and IMS-ToF-MS/MS.