Enzyme-inorganic nanoporous materials: Stabilization of proteins intercalated in α-zirconium(IV) phosphate by a denaturant

Improving the stability of proteins and enzymes at solid–liquid interfaces is challenging and it has important implications in biocatalysis and biosensors. Here, we report that moderate concentrations of urea stabilize heme proteins, such as met-hemoglobin (Hb) or met-myoglobin (Mb) bound to α-zirconium phosphate (α-ZrP). The half-life of Hb intercalated in the galleries of α-ZrP, for example, increased from 127 h (no urea) to >235 h (2 M urea). The peroxidase-like activity of Hb intercalated in α-ZrP was also improved by the addition of urea, and the product yields increased from 44% (no urea) to 79% (2 M urea). These improvements are not limited to Hb, and similar results also observed with Mb. Urea also inhibited the dithionite reduction of the ferric form of the intercalated heme proteins to their corresponding ferrous forms but not the oxidation of the ferric form to the corresponding high valent iron-oxo species. These observations open new possibilities to control the properties of immobilized proteins.