B George Barisas
ProfessorOffice: Chemistry C101Phone: 970-491-6641Website: http://www.chem.colostate.edu/bgbEducation: Ph.D., Yale UniversityEmail: George.Barisas@colostate.edu
Our research focuses on developing optical analytical techniques to study motions and distributions of molecules on living cell surfaces and on applying these methods to fundamental problems in the life sciences. We have one of the world’s best-equipped facilities for these techniques and are currently developing new methods of various sorts. Lateral motions of cell surface molecules reveal factors restraining these molecules and are measured by fluorescence photobleaching recovery and by single-molecule tracking microscopy. Molecular rotation on cell surfaces is an important parameter reflecting the size and aggregation state of membrane species and is examined by time-resolved phosphorescence anisotropy and fluorescence depletion anisotropy. Measurements of distances between specific molecules by fluorescence energy transfer and by sensitized photochemical labeling indicate how molecules communicate with one another in signal transduction. Many of our current problems involve signal transduction in cells of the immune system and in gonadotropin-responsive cells. Class II molecules of the Major Histocompatibility Complex are central to antigen presentation in T cell-dependent immune responses. The lateral and rotational dynamics and membrane distribution of Class II molecules have been implicated in signal transduction and antigen presentation. We are examining how various structural mutations introduced into Class II molecules by Dr. William Wade of Dartmouth Medical School affect their membrane dynamics and biological function. Another major project involves the MAFA protein of rat 2H3 mast cells which can inhibit triggering of these cells’ allergic responses, that is, their release of vasoactive amines. Protein rotational motion, lateral motion, intermolecular distances, and receptor-associated proteins are under study to characterize the interactions between MAFA and other membrane proteins. Examination of MAFA-derived chimeric molecules is helping us establish which parts of the molecule are responsible for particular functions. As one of the very few inhibitory systems characterized to date on cells of the immune system, the MAFA system is of potential clinical interest in allergy therapy. We also participate in collaborative projects in the area of animal reproduction. A major project of this type involves the luteinizing hormone receptor of cells of the corpus luteum and of Leydig cells. Proper function of this receptor system is essential during early pregnancy. In a joint project with Prof. Deborah Roess of the Colorado State University Department of Physiology, we are using optical techniques to explore how the luteinizing hormone receptor regulates fertility and how gonadotropins modulate events in receptor function including G-protein interactions, receptor internalization and cAMP activation.