Advances in ion mobility-mass spectrometry instrumentation and techniques for characterizing structural heterogeneity.

Over the last decade, the field of ion mobility-mass spectrometry (IM-MS) has experienced dramatic growth in its application toward ion structure characterization. Enabling advances in instrumentation during this time period include improved conformation resolution and ion sensitivity. Such advances have rendered IM-MS a powerful approach for characterizing samples presenting a diverse array of ion structures. The structural heterogeneity that can be interrogated by IM-MS techniques now ranges from samples containing mixtures of small molecules exhibiting a variety of structural types to those containing very large protein complexes and subcomplexes. In addition to this diversity, IM-MS techniques have been used to probe spontaneous and induced structural transformations occurring in solution or the gas phase. To support these measurement efforts, significant advances have been made in theoretical methods aimed at translating IM-MS data into structural information. These efforts have ranged from providing more reliable trial structures for comparison to the experimental measurements to dramatically reducing the time required to calculate collision cross sections for such structures. In this short review, recent advances in developments in IM-MS instrumentation, techniques, and theory are discussed with regard to their implications for characterization of gas- and solution-phase structural heterogeneity.