Sarah has a B.S. in both Chemistry and Environmental Studies from the University of the South in May 2014. During her undergraduate career, she studied the barnacle adhesion mechanism at the Naval Research Lab in Washington, DC. Sarah joined Brent Martin’s lab in the Chemistry Department at the University of Michigan, where she is working to improve data-independent proteomic methods to interrogate complex biological samples. Her current focus is optimizing traveling-wave ion mobility separation of tryptic peptides to improve proteome coverage.
Optimizing Ion Mobility Separation for Data-Independent Acquisition Proteomics
Ion mobility spectrometry (IMS) increases the peak capacity, sensitivity and resolving power of data-independent LC-MS proteomics. Optimization of separation in drift space for both peak capacity and resolution is crucial to maximizing the ability of LC-IMS-MS instruments to interrogate complex samples. In traveling wave ion mobility spectrometry (TWIMS), DC pulses are applied sequentially to stacked-ring ion guides within a confining RF field, creating a potential “wave” that pushes peptide ions through the nitrogen-filled mobility cell. Separation occurs due to differences in collisional cross-section between peptide ions. Wave heights and velocities can be chosen to manipulate the mobility separation. We have characterized the mobility separation of precursor peptide ions from a HeLa cell digest, measured mobility resolution and evaluated the contribution of TWIMS to peptide annotation under standard TWIMS parameters. The calculated peak capacity of the LC-TWIMS-MS system was 2.83 million peaks, a 65% increase over LC-MS alone. Current work includes optimizing TWIMS conditions, along with ion accumulation times and TOF duty cycle to improve sampling and proteome coverage. These results help describe the utility and limitations of ion mobility separations for the analysis of complex mixtures.