The purpose of this project is to study the physical properties of a wide variety of biological macromolecules and correlate these properties to the structure and function of the macromolecules. The emphasis is on the thermodynamics of the interactions of these macromolecules and on their molecular sizes and shapes. Analytical ultracentrifugation and mathematical modeling are the principal research techniques used. Among the associated systems studied have been the multifunctional chromagranins A and B, the cell cycle regulatory protein p53, T-cell receptors, DNA repair proteins, HIV-1 integrase, and CD4 binding to the C4 domain of HIV gp120.