UREA UNFOLDING AND STABILITY OF GAMMA-II CRYSTALLIN

The conformational stability of gamma-II crystallin at pH 7.0 was esti mated by studying its urea denaturation at isothermal conditions. The conformational states were monitored by far UV-CD and fluorescence mea surements. Gamma-II crystallin shows sigmoidal order-disorder transiti on curves by both methods. The presence of more than one intermediate was confirmed but at neutral pH. The experiment results were criticall y analyzed in terms of both linear extrapolation and Tanford's models. The Gibbs free energy of unfolding DELTAG(u,H2O) = -36 kcal mol-1 was obtained. This value corresponds to the high conformational stability of the protein predicted qualitatively by its crystal structure.