Our studies on polyomavirus, tobacco mosaic virus and gap junction membranes are focused on correlating their structures with the dynamic processes in their formation, interactions and stability. Analyses of disorder in simpler protein structures will exemplify the molecular movements involved in the switching mechanisms of virus and membrane assemblies. Our studies involve the coordinated applications of methods of X-ray diffraction, electron microscopy, physical biochemistry, molecular biology and computer graphics. Polyomavirus structure and assembly are being investigated by electron microscopy of self-assembling capsid proteins produced from the recombinant expression vector; by X-ray crystallography of the intact virion and recombinant capsid proteins; and by measurement of diffuse X-ray scattering from the disordered minichromosome core of crystalline virions. Tobacco mosaic virus asembly and interactions are being investigated by X-ray and electron crystallography to refine computer-generated models of the polymorphic disk aggegates; by correlating physical- chemical and structural data to analyze electrostatic interactions involved in switching assembly; and by optical and X-ray diffraction analysis of colloidal states or organization of viruses and protein particles. Gap junction connexion structure and gating mechanisms are being investigated by computer modeling of the beta-sheet structure of the connexon channel based on X- ray and electron crystallographic data; by measurement of variations in the surface structure; and by correlating structure and sequence data. Movement in macromolecular structures is being investigated by measurement of diffuse X-ray scatter from insulin and lysozyme crystals; by correlated X-ray diffraction, optical and model simulation of tropomyosin crystals; and by application of similar methods to disordered virus and membrane structures. Technological developments include use of the CCD- based X-ray area detector to record diffraction data that could not be obtained by conventional methods; and application of computer graphics mehtods to relate higher levels of organization to the underlying molecular structure.
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