Hydration of gamma-crystallins.

Four fractions of gamma-crystallins, B(II), C(IIIb), D(IIIa) and E(IVa), were isolated from bovine lenses. The hydration properties of each fraction were measured as a function of protein concentration. The freezable water content was obtained by differential scanning calorimetry and the total water content by thermogravimetric analysis. The difference yields the non-freezable (bound) water content of the crystallins. At physiological protein concentrations the order of the bound water content was C(IIIb) > D(IIIa) >> E(IVa) > B(II). This order was reversed between C and D and between B and E at low protein concentrations. This trend was evident whether the bound water was calculated as a percentage of the total water or as quantity per gram of gamma-crystallin.