Agilent 6560 IMS-QTOF mass spectrometer
An Agilent 6560 Ion Mobility Spectrometry (IMS) QTOF instrument system was installed in May, 2014. The system has a chip chromatography interface and combines an ion mobility drift cell with a high performance QTOF mass analyzer.
Ion mobility separates ions based on their collision cross sections, i.e., their shapes. If a molecule or molecular complex has multiple conformations, these can often be resolved from one another. Thus, changes in protein folding or differences in glycan branching can be detected and closely related molecules can be separated based on the variations in their shapes. These fundamental values can be measured and cataloged to be used as reference values or monitored to follow changes with respect to structural modifications, interactions, or environment. The figure below shows the separation and a mobilogram of the resolved species. An action version of the figure is available at the link: IMS-QTOF separation
We are building a library of IMS data for glycans and glycopeptides that should be useful for the assignment of free glycans and of glycopeptides in protease digests of biological samples. We have found that the mobilities of the glycoforms of each modified peptide can be plotted as straight lines, such as shown here (R. Glaskin et al., ASMS 2015):
The original instrument design allows for collision-induced decomposition of the mobility-resolved ions. In order to increase the options for structural determinations while preserving labile modifications, we are now investigating the possibility for fragmentation by electron activation (ExD) and have positioned a radiofrequency-free electromagnetostatic cell (V. G. Voinov et al., J. Am. Soc. Mass Spectrom., 2011, 22, 607-611) prior to the CID cell in this instrument, in collaboration with the group at Oregon State University/e-MSion Inc. who are developing this compact cell (R. Glaskin et al., ASMS 2016).
Installation of ECD cell mounted on CID cell in IMS-QTOF MS