This project is an interdisciplinary investigation of mechanisms by which a light stimulus is transformed into neural activity in the cells of the retina. In brief, what is known is that light is absorbed by the pigment, rhodopsin, which is then said to be in the photoactivated state. The photoactivated rhodopsin interacts with another molecule, the so-called G- protein, which in turn activates the enzyme, cyclic GMP phosphodiesterase, leading to the generation of nerve impulses by reasonably well understood processes. Little is known of the molecular arrangement of atoms within rhodopsin in the unactivated or photoactivated states, although it is known that rhodopsin consists of a protein to which a derivative of vitamin A, retinal, is attached. The results of this project will help to clarify the structures of unactivated and photoactivated rhodopsin and the nature of the attachment between retinal and the protein. The basic approach used in this work is to prepare synthetic organic molecules that will act as probes, competing with retinal for its binding site on the protein and "reporting" by their optical properties what the local environment is like in unactivated and photoactivated rhodopsin. These probes will not only provide valuable direct information about the process of light detection in vision in the hands of this investigator, they will also be made available to others for application in other kinds of experiments.
