title: Free-standing nanogold membranes as scaffolds for enzyme immobilization.
abstract: We demonstrate herein the formation of a free-standing gold nanoparticle membrane and its use in the immobilization of the enzyme, pepsin. The nanogold membrane is synthesized by the spontaneous reduction of aqueous chloroaurate ions at the liquid-liquid interface by the bifunctional molecule bis(2-(4-aminophenoxy)ethyl) ether (DAEE) taken in chloroform. This process results in the formation of a robust, malleable free-standing nanogold membrane consisting of gold nanoparticles embedded in a polymeric background. Recognizing that gold nanoparticles are excellent candidates for immobilization of enzymes, we have immobilized pepsin on the nanogold membrane, leading to a new class of biocatalyst. A highlight of the new pepsin-nanogold biocatalyst is the ease with which separation from the reaction medium may be achieved. The catalytic activity of pepsin in the bioconjugate was comparable to that of the free enzyme in solution. The pepsin-nanogold membrane bioconjugate material exhibited excellent biocatalytic activity over 10 successive reuse cycles as well as enhanced pH, temperature, and temporal stability.
authors.affiliation: Materials Chemistry, Biochemical Sciences, and Polymer Chemistry Divisions, National Chemical Laboratory, Pune-411 008, India.
authors.forename: Sumant
authors.initials: S
authors.lastname: Phadtare
authors.forename: V P
authors.initials: VP
authors.lastname: Vinod
authors.forename: Prakash P
authors.initials: PP
authors.lastname: Wadgaonkar
authors.forename: Mala
authors.initials: M
authors.lastname: Rao
authors.forename: Murali
authors.initials: M
authors.lastname: Sastry
mesh_terms: D002364:Caseins / Q000378:metabolism; D002384:Catalysis; D004795:Enzyme Stability; D004800:Enzymes, Immobilized / Q000737:chemistry* / Q000378:metabolism; D006046:Gold / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D046529:Microscopy, Electron, Transmission; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure; D010434:Pepsin A / Q000737:chemistry* / Q000378:metabolism; D013057:Spectrum Analysis; D013379:Substrate Specificity; D013696:Temperature; D014961:X-Ray Diffraction
chemical_list: D002364:Caseins; D004800:Enzymes, Immobilized; D006046:Gold; D010434:Pepsin A