Molecular recognition between biological macromolecules is thought often to occur through a transient intermediate known as an "encounter complex". In this complex, two reactants come into proximity and collide repeatedly. They do not necessarily form bonds with each other, but cannot easily escape because they are packed against each other by solvent. The investigator's long term goal is to develop experimental approaches to study encounter complexes. The investigator proposes a method for resolving encounter complex formation into component steps, and will apply this method to antibody recognition of antigens. The method is to construct monovalent and divalent versions of the same antibody and measure the kinetics of antigen binding by each. Loss of one binding site creates a deficit in reaction rate that affects the specific interaction with antigen, but not the general processes of diffusion and non-specific collisions. This theory will be tested with mutant antibodies and antigens, using primarily stopped-flow fluorescence to measure kinetics. The model system employed will be the antigen lysozyme and a humanized version of an anti-lysozyme antibody. These studies will elucidate new principles of ligand-receptor interaction that underlie the reactivity of antibodies and other molecules of the immune system.
The investigator proposes a new way of analyzing chemical reactions between complex biological molecules such as proteins. Macromolecules in water move about uneventfully for a long time, then undergo a rapid series of collisions when they meet each other. Two molecules engaged in this collision process are called an "encounter complex". Computer calculations indicate that the encounter complex is an important intermediate in crucial life processes, such as the recognition of foreign materials by antibodies. The investigator plans to test this theory experimentally, and to develop a general method of looking at the biological role of the encounter complex.
