The Williams Laboratory for Single Molecule Biophysics specializes in the development of single molecule methods for quantitatively probing the biophysical properties of DNA and RNA and for understanding the biophysics of their interactions with proteins and other DNA binding ligands. These methods are used to probe nucleic acid interactions in order to understand the role of these interactions in processes such as replication and transcription. Specifically, the lab studies single-stranded DNA binding proteins from viruses and bacteria, retroviral replication proteins such as HIV-1 nucleocapsid and Gag proteins, bacterial polymerases, small molecules that bind to DNA and may inhibit cellular replication, and nuclear proteins such as HMG proteins. At the heart of all of these studies is the search for the mechanism by which these proteins interact with DNA in order to alter its biophysical properties, thereby achieving their specific biological activity. In order to understand these mechanisms, these studies are done in collaboration with experts in each biological system, and the activities of the proteins are monitored in a variety of in vitro and in vivo studies to determine how the observed biophysical mechanism is manifested on the level of a more complete biological system.