A major impediment in the determination of high resolution protein structures by single particle cryo-electron microscopy has been the presence of sample heterogeneity. Oftentimes, heterogeneity is due the dynamic nature of protein complexes, which can exist in multiple different conformational states in solution. Recent advancements in cryo-electron image processing have provided tools to accurately sort vitrified protein complexes into distinct populations that can be subsequently used to determine structures corresponding to each of the subpopulations. Such sorting algorithms have allowed high resolution structures of multiple conformations to be elucidated from a single cryo-electron microscopic grid. Besides sorting different conformations, classification can also be used to assess the influence of specific perturbations upon conformational state at level of individual protein complexes. By modulating the concentrations of different components of the system prior to vitrification, it is possible to measure the fraction of complexes belonging to each conformational state as a function of the concentration of each component and thus characterize how specific components influence the equilibrium between conformational states.
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Richard Hite, PhD
Richard Hite is an assistant member in the Structural Biology Program at Memorial Sloan Kettering Cancer Center, where his lab characterizes the molecular mechanisms that control ion channel function. Richard received his Ph.D. in 2010 in the laboratory of Thomas Walz, Ph.D., at Harvard Medical School where he used electron crystallography of aquaporin-0 two-dimensional crystals to analyze the structural basis of annular lipid-protein interactions at high resolution. Richard performed his postdoctoral studies in laboratory of Roderick MacKinnon, M.D., at Rockefeller University, where he used single-particle cryo-electron microscopy, X-ray crystallography and electrophysiological approaches to study ligand- and voltage-gated potassium channels.