Sol−Gel Encapsulated Horseradish Peroxidase:  A Catalytic Material for Peroxidation

Abstract

This study addresses the viability of sol-gel encapsulated HRP (HRP:sol-gel) as a recyclable solid-state catalytic material. Ferric, ferric-CN, ferrous, and ferrous-CO forms of HRP:sol-gel were investigated by resonance Raman and UV-visible methods. Electronic and vibrational spectroscopic changes associated with changes in spin state, oxidation state, and ligation of the heme in HRP:sol-gel were shown to correlate with those of HRP in solution, showing that the heme remains a viable ligand-binding complex. Furthermore, the high-valent HRP:sol-gel intermediates, compound I and compound II, were generated and identified by time-resolved UV-visible spectroscopy. Catalytic activity of the HRP:sol-gel material was demonstrated by enzymatic assays by using I(-), guaiacol, and ABTS as substrates. Encapsulated HRP was shown to be homogeneously distributed throughout the sol-gel host. Differences in turnover rates between guaiacol and I(-) implicate mass transport of substrate through the silicate matrix as a defining parameter in the peroxidase activity of HRP:sol-gel. HRP:sol-gel was reused as a peroxidation catalyst for multiple reaction cycles without loss of activity, indicating that such materials show promise as reusable catalytic materials.

Site‐Specific Patterning of Biomolecules and Quantum Dots on Functionalized Surfaces Generated by Plasma‐Enhanced Chemical Vapor Deposition

“…[29] For example, the immobilization of enzymes can offer such improvements when constrained on self-assembled monolayers, [30] nanoparticle/colloidal surfaces, [29,31] and sol-gel surfaces. [32] We examined the effect of enzyme immobilization onto the PECVDpatterned substrate. Horseradish peroxidase (HRP), a commonly used enzyme, was immobilized on the NH 2 -SAM/ppbenzene patterned surface.…”

Uterine Peroxidase-Catalyzed Formation of Diquinone Methides from the Selective Estrogen Receptor Modulators Raloxifene and Desmethylated Arzoxifene

“…The interaction between H 2 O 2 and the protoheme group located at the active site of peroxidases generates an oxo ferryl protophyrin-cation radical (compound I) which oxidizes the substrate (43). However, oxidation of raloxifene and DMA in uterine microsomes was only modestly enhanced by addition of exogenous H 2 O 2 .…”

Silica Sol-Gel Entrapment of the Enzyme Chloroperoxidase

“…For example, preequilibration with 72 mM pyrogallol for 3 hours in comparison to using 35 mM pyrogallol without preequilibration increased the relative activity from 12.3 to 19.6%. The strategy to preequilibrate enzyme sol-gel materials with an excess of substrate before adding a cosubstrate was already successfully applied by Smith and coworkers [23] in their study on sol-gel encapsulated horseradish peroxidase. Based on the data presented in Figure 1(a), however, we would not expect an increase in catalytic performance for sol-gel entrapped CPO as the pyrogallol concentration is raised from 35 to 72 mM.…”

“…Enzyme immobilization offers key advantages, most notably ease of enzyme recovery and reusability [22]. Silica-based sol-gels furnish chemically inert and optically transparent immobilization matrices [2,23]. However, sol-gel immobilization is often accompanied by a loss of enzymatic activity.…”