This contract will purchase new computer software, upgrades to existing software licenses and software maintenance to support the research efforts of the Basic Research Branch of the National Center for Biotechnology Information (NCBI). The specific areas of interest for this contract action are computational and graphical modeling of biological macromolecules. The software acquired through this contract will run on an existing network of server and workstation computers from Silicon Graphics. These systems are specialized for computer-intensive and three-dimensional graphics-intensive applications, and are thus well suited for molecular modeling software.