Understanding the details of enzyme behavior at solid surfaces is essential for the rational design of synthetic materials for their use as biosensors, implants, enzyme reactors, and biomedical devices. To make progress toward this goal, a home-built wavelength dependent SPR was used to study enzyme behavior on bare gold in the presence and absence of an ultra-thin film of inorganic materials such as a-Zr(HPO₄).H₂O (abbreviated as a-ZrP). Yeast-iso-1-Cytochrome c (Cyt c), for example, was immobilized on gold through Cys-102. The inorganic materials were then adsorbed onto a monolayer of protein prepared on a Au substrate (SPR, figure below). The DG˚ for the denaturation of Cyt c, obtained from the SPR studies, indicated that the protein bound to the Au surface is less stable than in solution, but the adsorption of the inorganic layer enhanced its stability by more than 1 kcal/mol. In an independent approach, a-ZrP was covalently built on gold and the protein adsorption kinetics were studied in real time. These are the very first studies to directly measure protein-inorganic interactions, and they provide some of the first attempts in directly monitoring protein kinetics and stability at well-defined solid surfaces.

Figure: SPR chip fabrication by adsorption of Cyt c on Au (red circle) followed by adsorption of exfoliated a-ZrP (blue rectangle).