Preparation and catalytic evaluation of cytochrome c immobilized on mesoporous silica materials

Cytochrome c (cyt. c, molecular size of 2.5 nm × 2.5 nm × 3.7 nm) was immobilized on six types of mesoporous silicates (MPS), having pore sizes from 2.8 to 15.0 nm, and their catalytic activities were evaluated by oxidation of thioanisol with H2O2. Among the silica materials, cyt. c immobilized on MPS pore size of 3.4 nm) showed the best catalytic activity, and its relative activity was improved 1.7 times over that of cyt. c solution. Enhancement of catalytic activity was obtained by immobilization on MPS having a similar size (mesopore) to the molecular size of cyt. c. Activity stability of cyt. c was also evaluated under the various conditions that caused protein inactivation, like HCl, urea, methanol, and guanidine. As results, stability was improved by the immobilization on silica material having a larger pore size (15.0 nm), offered an environment for encapsulating entire cyt. c molecules, inhibiting cyt. c from unfolding and irreversible decomposition.