title: Catalytic properties of thioredoxin immobilized on superparamagnetic nanoparticles.
abstract: Thioredoxin (Trx1), a very important protein for regulating intracellular redox reactions, was immobilized on iron oxide superparamagnetic nanoparticles previously coated with 3-aminopropyltriethoxysilane (APTS) via covalent coupling using the EDC (1-ethyl-3-{3-dimethylaminopropyl}carbodiimide) method. The system was extensively characterized by atomic force microscopy, vibrational and magnetic techniques. In addition, gold nanoparticles were also employed to probe the exposed groups in the immobilized enzyme based on the SERS (surface enhanced Raman scattering) effect, confirming the accessibility of the cysteines residues at the catalytic site. For the single coated superparamagnetic nanoparticle, by monitoring the enzyme activity with the Ellman reagent, DTNB=5,5'-dithio-bis(2-15 nitrobenzoic acid), an inhibitory effect was observed after the first catalytic cycle. The inhibiting effect disappeared after the application of an additional silicate coating before the APTS treatment, reflecting a possible influence of unprotected iron-oxide sites in the redox kinetics. In contrast, the doubly coated system exhibited a normal in-vitro kinetic activity, allowing a good enzyme recovery and recyclability.
authors.affiliation: Instituto de Quimica, Universidade de Sao Paulo, Sao Paulo, Brazil.
authors.forename: Caterina G C M
authors.initials: CG
authors.lastname: Netto
authors.forename: Eduardo H
authors.initials: EH
authors.lastname: Nakamatsu
authors.forename: Luis E S
authors.initials: LE
authors.lastname: Netto
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Novak
authors.forename: Andre
authors.initials: A
authors.lastname: Zuin
authors.forename: Marcelo
authors.initials: M
authors.lastname: Nakamura
authors.forename: Koiti
authors.initials: K
authors.lastname: Araki
authors.forename: Henrique E
authors.initials: HE
authors.lastname: Toma
mesh_terms: D002234:Carbodiimides / Q000737:chemistry; D002384:Catalysis; D004228:Dithionitrobenzoic Acid / Q000737:chemistry; D006046:Gold / Q000737:chemistry; D055767:Immobilized Proteins / Q000737:chemistry*; D007700:Kinetics; D058185:Magnetite Nanoparticles / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry; D018625:Microscopy, Atomic Force; D008958:Models, Molecular; D011437:Propylamines; D012821:Silanes / Q000737:chemistry; D013059:Spectrum Analysis, Raman; D013879:Thioredoxins / Q000737:chemistry* / Q000378:metabolism
chemical_list: C518491:1-ethyl-3-(3-(diethylamino)propyl)carbodiimide; D002234:Carbodiimides; D055767:Immobilized Proteins; D058185:Magnetite Nanoparticles; D011437:Propylamines; D012821:Silanes; D013879:Thioredoxins; D006046:Gold; D004228:Dithionitrobenzoic Acid; C477625:amino-propyl-triethoxysilane