Effects of surface functionalization and organo-tailoring of synthetic layer silicates on the immobilization of cytochrome c

The utility of various synthetic hectorites for the preparation of active enzyme complexes by simple adsorption processes was examined. The smectites compared include commercially available Laponite RD, mesostructured hectorites (both with and without organic template), and silane-modified mesostructured hectorite. The complexes were evaluated by the amount of cytochrome c that was incorporated and the fraction of enzyme available for redox reaction. The quantity of adsorbed cyt c was determined by optical absorption spectroscopy of the supernatant solution, yielding enzyme densities that ranged from 20 to 50 wt %. There was no correlation between weight percent loading and either the surface area or the pore volume of the clay mineral. Rather, other characteristics such as surface compatibility appear to play the major role in this regard. Immobilized enzyme conformation was examined by EPR. Qualitative information regarding protein stability and redox activity was also obtained by chemical reduction experiments. These studies revealed the effects of organo-tailoring of the inorganic surface in terms of steric hindrance of enzyme in active conformation and denaturation within a clay pore microenvironment.