CAREER: High-Resolution Multidimensional Nonlinear Ion Mobility Spectrometry for Analytical Separations and Structural Characterization

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This CAREER award from the Chemical Measurement & Imaging Program (with co-funding from the Instrument Development for Biological Research Program) supports the efforts of Professor Alexandre Shvartsburg at Wichita State University to develop new technologies for the characterization of biomaterials. Mass spectrometry (MS) is a technique used to identification and characterization biological and environmental samples. To enable application to complex samples, MS is usually preceded by a separation step, typically employing solution-based methods of liquid chromatography or electrophoresis. These methods are increasingly being replaced or complemented by much faster separations based on gas-phase ion mobility spectrometry (IMS), which can provide additional insight into elements of ion structure. Dr. Shvartsburg and his group are advancing the capabilities of IMS based on fundamentally new measurement concepts. The research is integrated with an educational program centered on an IMS exhibit in the Wichita Exploration Place and other science museums and discovery centers nationwide, and taken to schools as part of a K-12 outreach program. The exhibit emulates IMS separations demonstrating the key aspects of resolution and sensitivity in an interactive format. This effort is complemented by a summer program for faculty from undergraduate institutions and community colleges in Kansas, providing them with opportunities to learn more about MS, IMS, and their applications. Incorporation of this knowledge into courses taught at their home institutions may help prepare students to contribute to a technology-based economy.Initial IMS methods were designed such that measured ion velocities are linearly proportional to the applied electric field. The relationship between field strength and velocity becomes more complex in strong fields, where ion mobility varies with field strength, enabling a newer technique called field asymmetric waveform IMS (FAIMS) that sorts ions by the difference between mobilities at high and low fields. FAIMS is capable of providing exceptionally fine separations, extending, in favorable cases, to separations of isotopic isomers (isotopomers). Dr. Shvartsburg is pursuing multiple approaches to advancing the resolving power of FAIMS by expanding the nonlinear IMS paradigm in fundamentally novel ways. One approach is higher-order differential IMS employing more complex asymmetric waveforms to achieve unique separations. Another is IMS with alignment of dipole direction, where the pendular locking of macromolecular dipoles permits capturing the directionally (rather than orientationally) averaged cross sections for more detailed structural characterization. Implementation of FAIMS at reduced temperatures may extend the pendular regime to smaller ions (including essentially all peptides) and avoid heating ions above room temperature, which can cause dissociation or structural distortion in high-field IMS systems. Assembly of multidimensional separations comprising linear and nonlinear IMS stages is central to this work. By devising and sharing teaching tools related to these sophisticated concepts, Dr. Shvartsburg is not only advancing our characterization capabilities, but also helping prepare students with the skills and understanding needed to advance the state of technology.