[Dielectric dispersions of alpha, beta H, beta L and gamma crystallin solutions]

The crystallins which constitute the major soluble proteins of the lens are known to change into insoluble proteins in aged or cataractous lenses. Such changes would affect protein-bound water and bulk water around the crystallin molecules. We measured the a.c. admittances of several kinds of crystallin, solutions in the frequency range from 10 kHz to 2 GHz to define the passive electrical properties of bound water. With the experimental data, we calculated the relative permittivity, conductivity, and loss factor. The admittance of crystallin solutions had essentially three dielectric dispersions and we could divide them into three dependent dispersions by a curve-fitting analysis based on a three-term Cole-Cole equation. The lowest frequency dispersion around a few MHz was due to protein particles, the middle frequency of the 10-100 MHz range to bound water, and the highest frequency of over 1 GHz to bulk water. The dielectric behavior of crystallin molecules and bound water depended on the protein concentration. With the increase in molecular weight of crystallins, the dielectric increments of both dispersions increased and the characteristic frequencies of the dispersions decreased significantly.