Our studies on polyoma virus, membrane gap junctions, tobacco mosaic virus and filamentous bacteriophage are focused on correlating their structures with the dynamic processes in their formation, interactions and stability. Coordinated X-ray diffraction, electron microscopy, spectroscopy and physico-chemical methods are being applied in these studies. Polyoma virus structure is being analyzed by X-ray crystallography of the intact virion and empty protein capsid to determine details of the structure and packing of the 72 pentameric capsomeres that build this icosahedrally symmetric structure. Low-irradiation electron micrographs of tubular polymorphic polyoma capsomere assemblies are being processed to characterize the variable bonding interactions. Model building will be used to correlate structural information about the switching in bonding specificity of polyoma capsomeres obtained by X-ray diffraction and electron microscopy. Improved methods of purifying and orienting gap junction specimens are making possible systematic X-ray diffraction and electron microscope studies of controlled structual and chemical modifications related to the mechanisms that regulate intercellular communication. The Beta-sheet conformation of the connexon protein is being characterized from the high angle X-ray diffraction. Chemical modification of tyrosine residues in tobacco mosaic virus and filamentous bacteriophage is being studied by spectroscopic titration to relate electrostatic interaction with the structure. Interparticle interactions in liquid and colloid crystalline phases of rod-shaped viruses oriented in magnetic field are being studied by light and X-ray scattering. A TV area detector will be used for diffraction measurements on virus and membrane specimens that could not be carried out by photographic recording.
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