Specific aims of the project are twofold: (1) to study the three-dimensional structure (conformation) of lens protein in solution, and (2) to study changes in chemical properties and the conformation upon application of cataractogenic agents such as ultraviolet light, sugar molecules, and calcium ion. Spectroscopic methods such as absorption, fluroescence, and circular dichroism, will be used for conformational studies. Biochemical techniques, including light scattering and sedimentation equilibrium will be used for aggregation or crosslinking studies. Little is known of the conformation and intermolecular interactions of the lens proteins that give rise to the supramolecular organization of the normal lens responsible for transparency. Any change in the three-dimensional structure of the proteins can cause the loss of this organized structure and lead to opacity (cataract). During aging and cataractogenesis, lens proteins undergo a number of modifications, including pigmentation and aggregation. In a diabetic cataract, the level of sugar in the lens is high. Sugar itself or its metabolites can cause aggregation leading to cataract formation. The level of calcium is also high in the cataractous lens. It has been proposed that the ultraviolet light from the sunlight is one factor responsible for age-related changes of lens protein and senile cataract. Hence, as a model for diabetic and senile cataract, the project plans to investigate the changes in physicochemical properties of lens protein upon in vitro application of those cataractogenic agents. The long-term objective of this proposal is to define the molecular arrangements of normal lens proteins responsible for transparency and also to define a molecular mechanism for the lens changes during cataract formation.
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