Advancing Cyclic Ion Mobility Mass Spectrometry Methods for Studying Biomolecules: Toward the Conformational Dynamics of Mega Dalton Protein Aggregates.

Native mass spectrometry is a powerful tool for the analysis of noncovalent complexes. When coupled with high-resolution ion mobility, this technique can be used to investigate the conformational changes induced in said complexes by different solution or gas-phase conditions. In this study, we describe how a new-generation high-resolution ion mobility instrument equipped with a cyclic ion mobility cell can be utilized for the analysis of large biomolecular systems, including temperature-induced protein aggregates of masses greater than 1.5 MDa, as well as a 63 kDa oligonucleotide complex. The effects of and the interplay between the voltages applied to the different components of the cyclic ion mobility spectrometry system on ion transmission and arrival time distribution were demonstrated using biomolecules covering the m/z range 2000-10,000. These data were used to establish a theoretical framework for achieving the best separation in the cyclic ion mobility system. Finally, the cyclic ion mobility mass spectrometer was coupled with a temperature-controlled electrospray ionization source to investigate high-mass protein aggregation. This analysis showed that it was possible to continuously monitor the change in abundance for several conformations of MDa aggregates with increasing temperature. This work significantly increases the range of biomolecules that can be analyzed by both cyclic ion mobility and temperature-controlled electrospray ionization mass spectrometry, providing new possibilities for high-resolution ion mobility analysis.