EPR characterization of cellulose triacetate fibers used for enzyme immobilization.

EPR studies of a nitroxide spin label and of the nitroxide spin-labeled albumin entrapped in cellulose triacetate fibers were carried out.The EPR spectra have shown that within the fiber only two phases are present: a liquid one of medium viscosity trapped inside microcavities, and a polymeric one surrounding them.After entrapment, spin-labeled albumin is distributed mainly in the liquid phase, though a not negligible amount of it remains within the polymeric matrix.The EPR studies have shown that, after the standard procedure of drying, the albumin is almost completely precipitated, but about 85% of it returns to solution when the fiber is again placed in the solution.The behavior of the albumin dissolved inside the microcavities toward denaturating agents and pH change, and that of the free albumin in solution is similar; the minor differences noticed indicate a second-order interaction between the fiber and the protein.