Project: Research project

Project Details


We wish to understand the molecular basis of visual transduction.
In particular, we intend to study in depth (1) the key light to
chemical energy conversion step, the rhodopsin to bathorhodopsin
transition, and (2) the first steps in the transducin chemical
cascade reaction leading to rod cell hyperpolarization which is
catalyzed by excited rhodopsin. In order to accomplish these
goals, we propose here several experiments employing state-of-
the-art spectroscopic techniques which yield very detailed
molecular information. Resonance Raman and very fast
(subpicosecond and picosecond) absorption and fluorescence
techniques will be used to study the rhodopsin to bathorhodopsin
photoreaction. The resonance Raman spectra of octopus
rhodopsin and bathorhodopsin, and isotopically labelled
derivatives, and the insect rhodopsin, Ascalaphus macaronius, will
be obtained in order to see if the molecular concepts developed
for the well studied bovine system can be generalized to different
species. The rhodopsin to bathorhodopsin transition has not been
kinetically resolved. Knowledge of whether or not proton
translocation accompanies the rhodopsin to bathorhodopsin
photoreaction and understanding the molecular dynamics of this
step can only be obtained by kinetic measurements. We believe
our 0.2 psec absorption spectrometer should be able to resolve
this key step. The most novel work described in this proposal is
the application of very sensitive classical Raman difference
techniques, recently developed in our laboratory, to obtain the
Raman spectra of GDP and GTP when bound to transducin, T.
The exchange reaction T.GDP+GTP yields T.GTP+GDP, catalyzed
by excited rhodopsin, is the first step in amplification of the light
absorption event. The Raman spectra of bound GDP and GTP
should provide a great deal of information on how the reaction
takes place.
Effective start/end date12/31/896/30/97


  • Medicine(all)
  • Spectroscopy