Rational design of a bivalent inhibitor

ORGN 698

Gregory H. Bird, ghbst3@pitt.edu and Christian E. Schafmeister, meister@pitt.edu. Department of Chemistry, University of Pittsburgh, 219 Parkman Ave, Pittsburgh, PA 15260
Our building-block approach for creating nanometer scale molecules consists of linking cyclic monomers containing two stereocenters by pairs of amide bonds. By assembling sequences of monomers having different stereochemistry, we can synthesize molecules that have a desired shape. Towards the application of polyvalent display of ligands, our methodology allows us to present a pair of ligands with control of both distance and orientation. Starting from the crystal structure coordinates for the pentameric Cholera Toxin, Beta subunit bound to a synthetic ligand and using molecular modeling software, we evaluated thousands of structures, in silico, for the ability to direct a pair of ligands into an ideal binding geometry. In order to judge how well the predicted “score” relates to an actual binding event, we attached a fluorescein tag to one end of the bivalent inhibitor and used fluorescence polarization to measure the dissociation constant. In essence, we are exploiting our abilities to quickly construct molecules that are rigid and adopt a predictable conformation in order to probe, with angstrom precision, the ideal binding geometry of a bivalent binding inhibitor.