Dielectric studies of native, unfolded and intermediate forms of beta-lactamase

Time-domain dielectric spectroscopy has been applied to native, intermediate and unfolded beta -lactamase structures both in the hydrated solid state and in solution. Gravimetric and dielectric measurements indicate that nearly three times as many water molecules are multiply hydrogen bonded to the unfolded compared with the native protein. By contrast, the primary hydration population of the state A intermediate is only 20% larger than that of the folded enzyme. Analysis of the beta -dispersions in terms of rotational relaxation of the protein's permanent dipole has indicated that there is no significant difference in the dimensions of the three structures. This is not consistent with the findings of previous studies employing different experimental techniques.