Photon correlation spectroscopy and light scattering of eye lens proteins at high concentrations

The bovine eye lens protein, alpha L crystallin, has been studied with photon correlation spectroscopy and statical light scattering in the concentration range up to 200 g/l in different solvent conditions. At higher concentration (c greater than 70 g/l) the scattering behavior is quite complicated, which results in nonexponential correlation functions. Three methods have been used for the analysis of these correlation functions, namely, cumulant analysis, sum of two exponentials analysis, and exponential sampling method. These methods resulted in very similar results. The highly concentrated solutions contain two scattering entities: the single alpha L crystallin and a rather heterogeneous population of large clusters. The statical light-scattering experiments can be interpreted in the same way and gave consistent results for the dimensions of the large scattering units. The formation of these clusters, which are strong light scatterers, is superimposed on an increasing degree of correlation between the bulk of the alpha L-crystallins, resulting in a net decrease of light scattering as a function of concentration.