title: Structure and activity of apoferritin-stabilized gold nanoparticles.
abstract: A simple method for synthesizing gold nanoparticles stabilized by horse spleen apoferritin (HSAF) is reported using NaBH(4) or 3-(N-morpholino)propanesulfonic acid (MOPS) as the reducing agent. AuCl(4)(-) reduction by NaBH(4) was complete within a few seconds, whereas reduction by MOPS was much slower; in all cases, protein was required during reduction to keep the gold particles in aqueous solution. Transmission electron microscopy (TEM) showed that the gold nanoparticles were associated with the outer surface of the protein. The average particle diameters were 3.6 and 15.4 nm for NaBH(4)-reduced and MOPS-reduced Au-HSAF, respectively. A 5-nm difference in the UV-Vis absorption maximum was observed for NaBH(4)-reduced (530 nm) and MOPS-reduced Au-HSAF (535 nm), which was attributed to the greater size and aggregation of the MOPS-reduced gold sample. NaBH(4)-reduced Au-HSAF was much more effective than MOPS-reduced Au-HSAF in catalyzing the reduction of 4-nitrophenol by NaBH(4), based on the greater accessibility of the NaBH(4)-reduced gold particle to the substrate. Rapid reduction of AuCl(4)(-) by NaBH(4) was determined to result in less surface passivation by the protein. Methods for studying ferritin-gold nanoparticle assemblies may be readily applied to other protein-metal colloid systems.
authors.affiliation: Department of Chemistry, University of Pennsylvania, 231 South 34th Street, Philadelphia, PA 19104-6323, USA.
authors.forename: Lei
authors.initials: L
authors.lastname: Zhang
authors.forename: Joe
authors.initials: J
authors.lastname: Swift
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Butts
authors.forename: Vijay
authors.initials: V
authors.lastname: Yerubandi
authors.forename: Ivan J
authors.initials: IJ
authors.lastname: Dmochowski
mesh_terms: D000818:Animals; D001052:Apoferritins / Q000737:chemistry*; D001881:Borates / Q000737:chemistry; D002384:Catalysis; D006046:Gold / Q000737:chemistry*; D017612:Gold Compounds / Q000737:chemistry; D006736:Horses; D007700:Kinetics; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D046529:Microscopy, Electron, Transmission; D009025:Morpholines / Q000737:chemistry; D053758:Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D036103:Nanotechnology / Q000379:methods
chemical_list: D001881:Borates; D017612:Gold Compounds; D009025:Morpholines; C008550:morpholinopropane sulfonic acid; D006046:Gold; D001052:Apoferritins; C010634:sodium borate