Rotational relaxation of free and protease-bound alpha2-macroglobulin

The recently described triplet probe depolarization technique has been utilized to investigated the rotational relaxation of free and protease-bound alpha2-macroglobulin. The molecular Stokes radius of the free globulin was found to be 88 A, a value which, when compared to the dry radius, indicates a high degree of hydration. The correlation time of alpha2-macroglobulin does not change after its binding with chymotrypsin, but slightly increases in the presence of plasmin. In the presence of 4 M urea, alpha2-macroglobulin dissociates into subunits and this dissociation does not lead to a release of the bound proteases.