|Division||Physical & Biological Sciences|
|Department||PBSci-Chemistry & Biochemistry Department|
|Campus Mail Stop||Chemistry|
Retinal Proteins, Photosensory Transduction, Membrane Bioenergetics, Photochemistry, Laser Flash Photolysis
Roberto Bogomolni's research focuses on the mechanisms of light energy conversion and light signal transduction in biological systems, and their evolution. Light is the primary source of energy in the biosphere as well as the stimulus that provides environmental information to living organisms. In the archaebacterium halobacterium halobium, both light energy conversion and light signal transduction are carried out by a family of intrinsic membrane proteins that contain retinal chromophores. Two of these rhodopsinlike proteins, bacteriorhodopsin (bR) and halorhodopsin (hR), are light-driven ion pumps (for protons and chloride, respectively). They harvest light energy and store it as a transmembrane electrochemical potential. In addition, H. halobium's motility is modulated by light, which can have an attractant or repellent effect, depending on wavelength. This primitive color-sensing mechanism enables the cell to migrate into an environment optimal for light absorption by bR and hR. The sensory photoreceptors are two additional retinal pigments, the sensory rhodopsins I and II (sR-I and sR-II), which are chemically similar to bR and hR but do not function as electrogenic ion pumps.
Functional characterization of these systems involves the measurement of light-driven ion translocation kinetics, stoichiometries, and quantum efficiencies in the intact cell and in cell membranes, or in purified pigments reconstituted into lipid vesicles. Cell swimming behavior and phototaxis are studied using computerized infrared video tracking techniques. In addition to conventional biochemical procedures for protein purification and sequencing, Bogomolni's group uses a variety of spectroscopic techniques to characterize the chromoproteins, their chromophores, and their photochemical reactions. These include absorption and fluorescence spectroscopy; laser flash photolysis in the ultraviolet, visible, and IR ranges; linear and circular dichroism; and resonance Raman and Fourier transform infrared spectroscopy. These studies are carried out in the native pigments and in chemically and genetically modified forms produced in the laboratory.
Biography, Education and Training
Diploma, University of Buenos Aires, Argentina
Ph.D., University of California, Berkeley
- G. I. Groma, R. A. Bogomolni, and W. Stoeckenius, "The Photocycle of Bacteriorhodopsin at High pH and Ionic Strength II. Time-Dependent Anisotropy Studied by Partially Saturating Photoselection," Bioch. Biophy. Acta 1319, 69-85, 1997.
- R. A. Bogomolni, W. Stoeckenius, I. Szundi, E. Perozo, K. D. Olson, and J. L. Spudich, "Removal of Transducer HtrI allows Electrogenic Proton Translocation by Sensory Rhodopsin I," Proc. Natl. Acad. Sci. U.S.A. 91, 10188, 1994.
- H. Tributsch and R. A. Bogomolni, "Bacteriorhodopsin: A Molecular Photooscillator?" Chem. Phys. Lett. 227, 74, 1994.
- R. Diller, M. Iannone, B. R. Cowen, S. Maiti, R. A. Bogomolni, and R. M. Hochstrasser, "Picosecond Dynamics of Bacteriorhodopsin Probed by Time-Resolved Infrared Spectroscopy," Biochemistry 31, 5567, 1992.
- S. P. A. Fodor, D. Baselt, R. van der Steen, J. Lugtenburg, R. A. Bogomolni, and R. A. Mathies, "Structure of the Retinal Chromophore in Sensory Rhodopsin from Raman Spectroscopy and Retinal Analogues," Biophys. J. 55, 255a, 1989.
- J. L. Spudich and R. A. Bogomolni, "Sensory Rhodopsins of Halobacteria," Annu. Rev. Biophys. Biophys. Chem. 17, 193, 1988.
- R. A. Bogomolni and J. L. Spudich, "The Photochemical Reactions of Bacterial Sensory Rhodopsin-I. Flash Photolysis Study in the One Microsecond to Eight Second Time Window," Biophys. J. 52, 1071, 1987.