This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. This project develops software that allows combined use of the Chimera visualization package and the EMAN package for electron microscocpy single particle reconstructions. The EMAN package calculates 3-dimensional density maps of molecular assemblies such as virus particles, ribosomes, ion channels and other cellular machinery by back-projecting random 2-dimensional views of thousands to hundreds of thousands of specimens. The EMAN package does not include 3-dimensional visualization, for which the Chimera software packages is used. Both EMAN and Chimera are used to perform analysis of 3-dimensional density maps -- segmenting the maps into individual molecular components and fitting atomic models obtained from crystallography. This project develops software that facilitates use of the complementary features of EMAN and Chimera such as Chimera user interface dialogs that run EMAN computations (e.g. locating helices in density maps) and display results in Chimera. The EMAN package is developed by an NCRR Biotechnology Research Resource called the National Center for Macromolecular Imaging (NCMI), directed by Wah Chiu.