Conformational changes of proteins in aqueous solution induced by temperature in the pre-melting region

In this paper we report dielectric measurements at radiofrequencies on aque ous solutions of three proteins (cytochrome, lysozyme and metmyoglobin) in the native state as a function of temperature in the interval 0-60 degreesC . From the analysis of dielectric relaxation of the protein solutions, the effective hydrodynamic radius r and the electric dipole moment mu of the pr oteins were calculated. The results show that temperature causes continuous gradual changes of r and mu, with a maximum at a temperature that is diffe rent for each protein. This effect in the pre-melting region seems to be ge neral and related to variations of thermodynamic parameters.