Abstract
Purpose:
To study the development of high concentration short-range order in beta crystallin solutions, and accompanying protein dynamics.
Methods:
Bovine beta crystallin fractions were isolated using size-exclusion chromatography of 1-2 week old calf lens homogenates, and studied using static and quasielastic light scattering of 633 nm wavelength light, at concentrations up to 250 milligrams/milliter (mg/ml). These measurements yield excess Rayleigh ratios, or absolute cross sections for light scattering, and corresponding collective diffusion coefficients.
Results:
For higher molecular weight fractions averaging 7x104 grams/mole, as determined from dilute concentration Rayleigh ratios, high concentration Rayleigh ratios plateau in the vicinity of 200 to 250 mg/ml, at close to 1.5 x 10-3 inverse centimeters, while low concentration scattering is intermediate between those of alpha and gamma crystallin solutions. Diffusion coefficients decrease in a nonlinear fashion from 5.5 x 10-11 m2/sec to 4 x 10-11 m2/sec over the same concentration range.
Conclusions:
The observed dependence of the Rayleigh ratios on concentration is consistent with the influence of repulsive interactions between beta crystallins, as reported previously, which can lead to short-range order at high concentrations.