Short range order of the crystallins does account for the transparency of the eye lens. To explain the solution structure of this highly concentrated protein solution on a quantitative basis, the hydrodynamic structure and the interparticle interactions of the proteins have to be known. For that purpose, the light scattering of concentrated solutions of alpha-crystallin has been studied. Starting from the detailed knowledge of the solution parameters of alpha-crystallin in diluted solutions, the structure of concentrated solutions up to 360 mg/ml has been studied using light scattering. Our results indicate that subtle changes in the macromolecular structure such as optical anisotropy or structural asymmetry for part of the alpha-crystallins, which results in solute light-scattering heterogeneity, can dramatically increase the light scattering by the alpha-crystallins and cause solution opacity.

We have studied diluted bovine eye lens alpha-crystallin solutions by using light scattering. The protein particles were modeled as hard spheres, showing electrostatic repulsion, due to surplus electric charges, and weak attractive interaction. The repulsive potential VR is defined by the radius of the particles, the Debye length kappa-1, and the number of charges at the Gouy layer; the attractive potential has been described by the London-van der Waals potential and is defined by the Hamaker constant A. We have used the diluted gas approximation and the one component macrofluid model to relate the experimental static factor Ki to the theoretical expression of the interaction potential V(x). This resulted in a Hamaker constant A of 0.06 +/- 0.01 KBT and an effective charge q ranging from 18 +/- 1 at low ionic strength (omega = 0.0022 M) to 50 +/- 5 at high ionic strength (omega = 0.1472 M).

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