Enthalpy and entropy of hydration of bovine crystallins.

Transparency of the lens of the eye is the result of a short range order in the packing of crystallin molecules within the fiber cells. Short range order depends on crystallin-crystallin as well as water-crystallin interactions. Light scattering measurements can provide information on the hydration of crystallins. Light scattering intensities were obtained as a function of scattering angle, concentration, and temperature on dilute solutions of beta H, beta L, and gamma fractions of bovine lens crystallins. The temperature dependence of the second virial coefficient was negative for the beta crystallin fractions and positive for the gamma fraction as well as that for alpha crystallin (Wang, X., and Bettelheim, F. A. (1989) Proteins Struct. Funct. Genet. 5, 166-169). The partial molar enthalpy values of the solutions were negative for the beta crystallin fractions, indicating a tendency for homo- and heterodimer and -oligomer association. The enthalpy values were positive for the alpha and gamma fractions. The negative values of the enthalpy of solutions differentiate the beta crystallins from the other crystallins. The partial molar entropy values of solutions of beta L and gamma fractions were identical, those of the oligomeric beta H fraction were higher, whereas those of alpha crystallin were a magnitude larger than those of the smaller crystallin molecules.