The Section on Membrane and Cellular Biophysics, led by Joshua Zimmerberg, studies membranes, viruses, organelles, cells, and tissues in order to understand the molecular organization of cellular membranes, the physico-chemical mechanisms of membrane remodeling, and the molecular anatomy of tissues, which will lead to a better understanding of viral, parasitic, metabolic, developmental, and neoplastic diseases. This past year, the Section's exocytosis project focused on a new method for the purification of synaptic vesicles, which contain a variety of proteins and lipids that mediate fusion with the pre-synaptic membrane. The Section also undertook two remodeling projects, one in collaboration with Sergey Bezrukov's Section on the optimization of receptors, and a second on the ultrastructural analysis of biological structures. Combining tomography with negative staining can provide three-dimensional images. The Section used methylamine tungstate to fulfill the basic requirements for a negative stain for tomography, namely, that the density and atomic number of the stain are optimal, and that the stain is not degraded with the intensive electron dose needed to collect a full set of tomographic images. Tomograms derived from multiple projections of EM images of the same structure yielded detailed images of single proteins on the surface of influenza A virus.
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