Most proteins, particularly those that accomplish complicated tasks, form assemblies with other proteins and molecules that are critical to their function. Established structural biology tools are most effective for highly purified samples that have limited conformational variability, which makes it challenging to apply those methods to capture a systems-wide understanding of the structures, interactions, and dynamics that are present under different cellular conditions. Mass spectrometry is fast, sensitive, tolerant of heterogeneity, and has great potential for assemblies that are extremely challenging to characterize using established tools and for high-throughput structural genomics.
Gas-Phase Structural Biology. Gas-phase ions of assemblies can retain significant memories of their native structures in solution. Many measurements of stoichiometry, connectivity, and shape have shown that these aspects of assembly structure can be strongly correlated in both environments. Gas-phase techniques, including mass spectrometry, ion mobility, and ion chemistry will be used to probe the structures of biological assemblies. Accurate models of assemblies, including those that are heterogeneous, dynamic, and/or membrane-bound, will be built based on results from both gas-phase and complementary techniques.
Gas-Phase Ion Chemistry. Although many native aspects of biological assembly structure are preserved in the corresponding gas-phase ions, clearly at least some reorganization will occur. Unfortunately, the extents and scales of this reorganization remain poorly understood. A detailed understanding of gas-phase biological assembly ion structure will be developed, with the goal of enabling more accurate and rapid translation of experimental observables into parameters with meaningful uncertainties for building structural models. New gas-phase methods for transforming and fragmenting these ions to gain complementary structural insights will also be developed.
Mass Spectrometry of Large Ions. Existing mass spectrometers for gas-phase structural biology yield spectra with decreased sensitivity and increased spectral congestion with increasing assembly size. We intend to develop an instrument for single-ion, gas-phase structural biology that is ideally suited for very large and heterogeneous assemblies that are beyond the reach of current instrumental platforms.