SUPRAMOLECULAR STRUCTURE OF THE MAMMALIAN LENS

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It has recently been demonstrated that the transparency of the mammalian lens is apparently due to short range order among the major proteins of the lens, the crystallins. An understanding of the nature of this order is an essential step in obtaining a molecular description of cataract formation (in which this order is disrupted). The major objective of this research is to describe intermolecular interactions between bovine lens crystallins in the form of a two dimensional spatial map of binary protein proximity relationships. This map will be generated by a systematic series of measurements employing three crystallin fractions. The potential existence of crystallin/crystallin interactions will be addressed within both homogeneous crystallin solutions and in all possible binary mixtures of crystallins as a function of protein concentration. The functional significance of any interactions detected will be evaluated based on the observation of the onset of increasing optical transparency seen at high protein concentrations in lens protein extracts. The selection of the experimental methods to be used is based on a desire to minimize perturbation of protein surfaces and a need to make measurements over an unusually wide range of protein concentrations. On this basis, the techniques of dynamic light scattering, chemical crosslinking and fluorescence energy transfer have been chosen to examine crystallin/crystallin interactions. The effect of calcium and sodium chloride will also be explored because of the known effects of these agents on the aggregation of crystallins. The resulting supra-molecular description of the lens in terms of the relative topological locations of the crystallins will then serve as a future framework within which to study cataract related phenomena.