The Imaging Core will provide the microscopy and imaging instruments and expertise to the individual Projects of Program Project Grant. The facilities and personnel of the Imaging Core are drawn from the Biomedical Imaging Group (BIG) at UMMS, a long established and productive group of researchers who have made significant contributions to cell biology through advances in high spatial and temporal resolution fluorescence microscopy, and the development of hardware, software, algorithms and techniques. The Imaging Core is located within the laboratory of the Biomedical Imaging Group, which is on the same floor as the laboratories of the other P.l.s of the Program Project. The central instruments provided are: 1) A Digital Imaging Microscope for multi-color, high-spatial resolution 3-D deconvolution imaging of fixed and living cells; 2) A unique, custom-built, multi-color, high-temporal resolution micrscope for fast 2-D, and 3-D deconvolution imaging of GFP (and variants) and otherfluorophores in living cells overtime; 3) A unique multi-color Total Internal Reflection Fluorescence Microscope (TIRFM) which can be combined with fast 3-D imaging, providing high-resolution images of the spatial domain close (< 300 nm, mean ~100 nm) to the plasma membrane in Iving cells; 4) custom deconvolution software developed by BIG and a Beowulf computing cluster to rapidly reconstuct 5-D (multi-color 3-D time series) images of living cells; 5) state-of-art color graphics workstations equipped with custom visualization and analysis software for 5-D image analysis; 6) Image archivial storage and retrieval file servers for safe on-line storage of the large (terabytes) amount of data generated by the Cores instruments and analysis programs. In particluar, the Core will provide continuing research and development of the imaging and analysis with TIRF microscopy as it is critical to the specific aims of Projects 1, 2 and 3. The five faculty members of the Core (1.1 FTE) will provide the Program Project investigators with expertise in: the design of imaging experiments including modifications to equipment, simulation, and testing of experimental protocols; design, modification and application of image processing algorithms and software for image analysis (much analysis of data is carried out by the core), and maintanence or modification of all neccesary Core resources, including opto-electronics, computers and software systems.