Optical clarity is a prerequisite for normal lens function. In broad terms this proposal addresses the question of how the biological functional integrity of the lens contributes to the physical requirements necessary for sustained transparency. The opaque lens, resulting from enhanced light scattering, is the medical condition of cataract. We propose to continue liquids and solids NMR studies of lens tissue and its purified crystallins which are aimed at the elucidation of the motional dynamics characteristics of both large and small molecules (and the affecting factors), such that lens protein organization and interaction can be inferred. Our intent is to forge a link to transparency. Because of lens heterogeneity some of the proposed NMR experiments will be performed on a spatially localized basis. 13C and 31P off-resonance rotating frame spin lattice relaxation experiments and the solid state NMR techniques of dipolar decoupling and cross polarization will be employed to assess the motional characteristics of lens proteins and phosphorus metabolites. The multiquantum spectral behavior of 23Na+ and 39K+ will be used to report on the surrounding macromolecular organization. Pulse gradient spin echo NMR experiments will permit elucidation of translational diffusion as well as the occurrence of restricted diffusion of lens water and selected phosphorus metabolites. Proton microimaging experiments will enable the acquisition of spatially localized lens water diffusion data. Particular emphasis will be directed to the elucidation of the organizational differences between the lens cortex and nucleus. Initial experiments will be performed with bovine lens homogenates, the intact lens, and purified alpha, beta, and gamma-crystallins. The potential interplay of metabolism with lens protein organization and interaction will be explored. The ancillary technique of resolution enhanced FTIR spectroscopy will be utilized in the proposed studies as a probe of protein structure. Bovine, rabbit, and human lens tissue will be utilized. Age will be a variable. Both the clear and cataractous lens will be studied. These studies will be extended to the X-ray, galactose, high Ca++, Tris, EGTA, and oubain induced experimental cataracts in the above animal models. The results of the proposed studies may provide the basic knowledge necessary to establish rationale for the identification f lenses with pre- cataractous changes. The ability to do so will permit an opportunity to initiate medical anticataract therapy and monitor efficacy of treatment.
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