Theoretical and experimental studies on the structure of vertebrate visual pigments
Tang, Li
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Permalink
https://hdl.handle.net/2142/18995
Description
Title
Theoretical and experimental studies on the structure of vertebrate visual pigments
Author(s)
Tang, Li
Issue Date
1996
Doctoral Committee Chair(s)
Ebrey, Thomas G.
Department of Study
Biophysics and Computational Biology
Discipline
Biophysics
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Molecular
Biophysics, General
Language
eng
Abstract
High resolution three dimensional structure of visual pigments is essential for understanding the visual process. The past few years have been an exciting period in the field of the structure of visual pigments. One of the significant achievements is the 9A projection map of bovine rhodopsin. However, its relatively low resolution does not allow one to pinpoint the residues that are directly involved in the retinal binding which are crucial for visual process. In this thesis, a theoretical model of the three dimensional structure of visual pigments has been established based on the 9A projection map of bovine rhodopsin and other existing experimental data. This new model differs from the ones which have so far been reported on many points and is consistent with a wider range of experimental results.
A key step in visual process is the interaction of membrane bound visual pigment with the transducin at the membrane surface. The electrostatic property of gecko photoreceptor membrane surface was probed by a pH sensitive dye covalently attached to the cytoplasmic side of the gecko P521, a cone pigment. The pH titrations of the bound dye at various bulk salt concentrations was carried out and the sign and magnitude of the surface charge density were determined based on Gouy-Chapman theory. My study suggested that the cytoplasmic side of gecko cone photoreceptor membrane carries a net negative charge, $-(3\pm1)$ and $-(1.54\pm0.05)$ per 1000 A$\sp2$ for the two labeling sites, respectively.
Zinc was found to be essential for vision in several in vivo experiments. However, its role is not well defined because the in vivo experiments were complicated by many unknown factors. In this thesis, the zinc effect on a visual pigment was studied. The results suggested that zinc does not affect visual process at the receptor level.
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