Ion mobility adds an additional dimension to mass spectrometric analysis of solution-phase hydrogen/deuterium...

The goal of this study was to determine the utility of adding ion mobility spectrometry to studies probing the solution-phase hydrogen/deuterium exchange (HX) of proteins. The HX profile of the Hck SH3 domain was measured at both the intact protein and the peptic peptide levels in the Waters Synapt HDMS system which uses a traveling wave to accomplish ion mobility separation prior to time-of-flight (Tof) m/z analysis. The results indicated a similar loss of deuterium with or without use of mobility in the Synapt and a level of deuterium loss comparable with a non-mobility Q-Tof instrument. The drift time of this small protein and its peptic peptides did not noticeably change due to solution-based deuterium incorporation. Importantly, ion mobility separations provided an orthogonal dimension of separation in addition to the reversed-phase high-performance liquid chromatography (RP-HPLC). The additional dimension of separation allowed for the deconvolution of overlapping isotopic patterns for co-eluting peptides and extraction of valuable deuterium incorporation data for those peptides. Taken together, these results indicate that including ion mobility separation in HX MS analyses further improves the mass spectrometry portion of such experiments.