Bioanalytical, Biophysical Chemistry
Professor in Chemistry
BS 1962, CUNY (City University of New York), PhD 1970, Rutgers University
Postdoc 1971-2, University of California-Irvine, Postdoc 1970-1, University of Massachusetts Amherst
149F Goessmann Laboratory
Principal Research Interests
Research in my group arises from my interest in polyelectrolytes, long-chain molecules in which every repeat unit carries a charge. Their unique properties reflect a combination of those of polymer solutions and salts. We focus on their interaction with oppositely charged nanoparticles such as dendrimers, surfactant micelles and proteins, with the objective of fundamental understanding of solution behavior. To do this we measure properties that can be quantitatively understood through basic physical relationships. Our work combines the disciplines of analytical, biological and physical chemistry.
Our experimental tools vary from very simple ones (turbidimetry), to more complex methods (light scattering, capillary electrophoresis, rheology, and various microscopies). To ensure reproducible results, we focus on equilibrium systems. One of our interests is the unique dense, viscous liquid phase “coacervates” that form spontaneously from polyelectrolytes with oppositely charged micelles or proteins. Polyelectrolyte-enzyme coacervates function as microreactors because the protein retains its native state and diffuses freely in the dense fluid coacervatge droplets. The surprising combination of high viscosity and fast diffusion arises from mesophase separation at the 300 nm length scale in these fluids. Polyelectrolyte-micelle coacervates also display unusual properties, phase separating by either heating or stress, a phenomenon known as “shear-banding.”
Biologically significant protein binding occurs with a group of polyelectrolytes known as glycosaminoglycans (GAGs). These mammalian polysaccharides are the most highly charged macromolecules in animals. Although they play a role in the action of many signaling proteins responsible for tissue regeneration, angiogenesis and cell differentiation, structure-property relations for GAGs are unknown. Unlike proteins and nucleic acids, they are never homogeneous and therefore never “pure,” so their characterization presents a huge challenge to classical biochemistry. We approach this problem with the model GAG-protein system of heparin-antithrombin, applying electrophoretic methods coupled with mass spectrometry and protein modeling.