title: 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.
authors.affiliation: Department of Chemistry, North Dakota State University, Fargo, North Dakota 58105, USA.
authors.forename: Kevyn
authors.initials: K
authors.lastname: Smith
authors.forename: Nathan J
authors.initials: NJ
authors.lastname: Silvernail
authors.forename: Kenton R
authors.initials: KR
authors.lastname: Rodgers
authors.forename: Timothy E
authors.initials: TE
authors.lastname: Elgren
authors.forename: Mauro
authors.initials: M
authors.lastname: Castro
authors.forename: Robert M
authors.initials: RM
authors.lastname: Parker
mesh_terms: D002384:Catalysis; D005292:Ferricyanides / Q000737:chemistry; D005296:Ferrous Compounds / Q000737:chemistry; D005782:Gels; D006418:Heme / Q000737:chemistry; D006735:Horseradish Peroxidase / Q000737:chemistry* / Q000378:metabolism; D010084:Oxidation-Reduction; D010545:Peroxides / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet; D013059:Spectrum Analysis, Raman
chemical_list: D005292:Ferricyanides; D005296:Ferrous Compounds; D005782:Gels; D010545:Peroxides; D006418:Heme; D006735:Horseradish Peroxidase; C053439:ferric ferricyanide