We report a dynamic light scattering study on protein suspensions of bovinelens homogenates at conditions (pH and ionic strength) similar to thephysiological ones. Light scattering data were collected at two temperatures,20 oC and 37 oC, over a wide range of concentrations from the very dilute limitup to the dense regime approaching to the physiological lens concentration. Acomparison with experimental data from intact bovine lenses was advancedrevealing differences between dispersions and lenses at similar concentrations.In the dilute regime two scattering entities were detected and identified withthe long-time, self-diffusion modes of alpha-crystallins and their aggregates,which naturally exist in lens nucleus. Self-diffusion coefficients aretemperature insensitive, whereas the collective diffusion coefficient dependsstrongly on temperature revealing a reduction of the net repulsiveinterparticle forces with lowering temperature. While there are no rigoroustheoretical approaches on particle diffusion properties for multi-component,non-ideal hard-sphere, polydispersed systems, as the suspensions studied here,a discussion of the volume fraction dependence of the long-time, self-diffusioncoefficient in the context of existing theoretical approaches was undertaken.This study is purported to provide some insight into the complex lightscattering pattern of intact lenses and the interactions between theconstituent proteins that are responsible for lens transparency. This wouldlead to understand basic mechanisms of specific protein interactions that leadto lens opacification (cataract) under pathological conditions.
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