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227 items found (0 items not approved), displaying 221 to 227.[First/Prev] 16, 17, 18, 19, 20, 21, 22, 23 [Next/Last]

Instruments / Technical Area	Publication Details	Published
	Microbial engineering of nanoheterostructures: biological synthesis of a magnetically recoverable palladium nanocatalyst Victoria S. Coker , James A. Bennett , Neil Telling , Torsten Henkel , John Charnock , Gerrit Van Der Laan , Richard Pattrick , Carolyn Pearce , Richard S. Cutting , Ian J. Shannon , Joe Wood , Elke Arenholz , Ian C. Lyon , Jon Lloyd Acs Nano 4 (5), 2577-2584 DOI: 10.1021/nn9017944 Show Abstract ▼ Abstract: Precious metals supported on ferrimagnetic particles have a diverse range of uses in catalysis. However, fabrication using synthetic methods results in potentially high environmental and economic costs. Here we show a novel biotechnological route for the synthesis of a heterogeneous catalyst consisting of reactive palladium nanoparticles arrayed on a nanoscale biomagnetite support. The magnetic support was synthesized at ambient temperature by the Fe(III)-reducing bacterium, Geobacter sulfurreducens, and facilitated ease of recovery of the catalyst with superior performance due to reduced agglomeration (versus conventional colloidal Pd nanoparticles). Surface arrays of palladium nanoparticles were deposited on the nanomagnetite using a simple one-step method without the need to modify the biomineral surface, most likely due to an organic coating priming the surface for Pd adsorption, which was produced by the bacterial culture during the formation of the nanoparticles. A combination of EXAFS and XPS showed the Pd nanoparticles on the magnetite to be predominantly metallic in nature. The Pd biomagnetite was tested for catalytic activity in the Heck reaction coupling iodobenzene to ethyl acrylate or styrene. Rates of reaction were equal to or superior to those obtained with an equimolar amount of a commercial colloidal palladium catalyst, and near complete conversion to ethyl cinnamate or stilbene was achieved within 90 and 180 min, respectively.	Apr 2010
I03-Macromolecular Crystallography	Structural basis of substrate binding in WsaF, a rhamnosyltransferase from Geobacillus stearothermophilus Kristin Steiner , Gregor Hagelueken , Paul Messner , Christina Schaffer , James H. Naismith Journal Of Molecular Biology 397 (2), 436-447 DOI: 10.1016/j.jmb.2010.01.035 PMID: 20097205 Open Access Show Abstract ▼ Abstract: Carbohydrate polymers are medically and industrially important. The S-layer of many Gram-positive organisms comprises protein and carbohydrate polymers and forms an almost paracrystalline array on the cell surface. Not only is this array important for the bacteria but it has potential application in the manufacture of commercially important polysaccharides and glycoconjugates as well. The S-layer glycoprotein glycan from Geobacillus stearothermophilus NRS 2004/3a is mainly composed of repeating units of three rhamnose sugars linked by α-1,3-, α-1,2-, and β-1,2-linkages. The formation of the β-1,2-linkage is catalysed by the enzyme WsaF. The rational use of this system is hampered by the fact that WsaF and other enzymes in the pathway share very little homology to other enzymes. We report the structural and biochemical characterisation of WsaF, the first such rhamnosyltransferase to be characterised. Structural work was aided by the surface entropy reduction method. The enzyme has two domains, the N-terminal domain, which binds the acceptor (the growing rhamnan chain), and the C-terminal domain, which binds the substrate (dTDP-β-l-rhamnose). The structure of WsaF bound to dTDP and dTDP-β-l-rhamnose coupled to biochemical analysis identifies the residues that underlie catalysis and substrate recognition. We have constructed and tested by site-directed mutagenesis a model for acceptor recognition.	Mar 2010
I04-Macromolecular Crystallography	The three-dimensional structure of [NiFeSe] hydrogenase from Desulfovibrio vulgaris Hildenborough: A hydrogenase without a bridging ligand in the active site in its oxidised, “as-isolated” state Marta C. Marques , Ricardo Coelho , Antonio L. De Lacey , Ines A. C. Pereira , Pedro M. Matias Journal Of Molecular Biology DOI: 10.1016/j.jmb.2009.12.013 PMID: 20026074 Diamond Proposal Number(s): [677] Show Abstract ▼ Abstract: Hydrogen is a good energy vector, and its production from renewable sources is a requirement for its widespread use. [NiFeSe] hydrogenases (Hases) are attractive candidates for the biological production of hydrogen because they are capable of high production rates even in the presence of moderate amounts of O2, lessening the requirements for anaerobic conditions. The three-dimensional structure of the [NiFeSe] Hase from Desulfovibrio vulgaris Hildenborough has been determined in its oxidised “as-isolated” form at 2.04-Å resolution. Remarkably, this is the first structure of an oxidised Hase of the [NiFe] family that does not contain an oxide bridging ligand at the active site. Instead, an extra sulfur atom is observed binding Ni and Se, leading to a SeCys conformation that shields the NiFe site from contact with oxygen. This structure provides several insights that may explain the fast activation and O2 tolerance of these enzymes.	Jan 2010
NONE-No attached Diamond beamline	Harnessing the extracellular bacterial production of nanoscale cobalt ferrite with exploitable magnetic properties Carolyn Pearce , Floriana Tuna , Richard Winpenny , Jon Lloyd , Elke Arenholz , Vicky Coker , Richard Pattrick , Neil Telling , Gerrit Van Der Laan Acs Nano 3 (7), 1922-1928 DOI: 10.1021/nn900293d Show Abstract ▼ Abstract: Nanoscale ferrimagnetic particles have a diverse range of uses from directed cancer therapy and drug delivery systems to magnetic recording media and transducers. Such applications require the production of monodisperse nanoparticles with well-controlled size, composition, and magnetic properties. To fabricate these materials purely using synthetic methods is costly in both environmental and economical terms. However, metal-reducing microorganisms offer an untapped resource to produce these materials. Here, the Fe(III)-reducing bacterium Geobacter sulfurreducens is used to synthesize magnetic iron oxide nanoparticles. A combination of electron microscopy, soft X-ray spectroscopy, and magnetometry techniques was employed to show that this method of biosynthesis results in high yields of crystalline nanoparticles with a narrow size distribution and magnetic properties equal to the best chemically synthesized materials. In particular, it is demonstrated here that cobalt ferrite (CoFe2O4) nanoparticles with low temperature coercivity approaching 8 kOe and an effective anisotropy constant of ?106 erg cm?3 can be manufactured through this biotechnological route. The dramatic enhancement in the magnetic properties of the nanoparticles by the introduction of high quantities of Co into the spinel structure represents a significant advance over previous biomineralization studies in this area using magnetotactic bacteria. The successful production of nanoparticulate ferrites achieved in this study at high yields could open up the way for the scaled-up industrial manufacture of nanoparticles using environmentally benign methodologies.	Jun 2009
	Today's wastes, tomorrow's materials for environmental protection L. E. Macaskie , I. P. Mikheenko , P. Yong , K. Deplanche , M. Paterson-Beedle , V. S. Coker , C. I. Pearce , R. A. D. Pattrick , D. Vaughan , G. Van Der Laan , J. R. Lloyd Advanced Materials Research 71-73, 541-548 DOI: 10.4028/www.scientific.net/AMR.71-73.541 Show Abstract ▼ Abstract: Over the past 30 years the literature has burgeoned with bioremediation approaches to heavy metal removal from wastes. The price of base and precious metals has dramatically increased. With the resurgence of nuclear energy uranium has become a strategic resource. Other ‘non-carbon energy’ technologies are driven by the need to reduce CO2 emissions. The ‘New Biohydrometallurgy’ we describe unites these drivers by the concept of conversion of wastes into new materials for environmental applications. The new materials, fashioned, bottom-up, into nanomaterials under biocontrol, can be termed ‘Functional Bionanomaterials’. This new discipline, encompassing waste treatment along with nanocatalysis or other applications, can be summarized as ‘Environmental Bionanotechnology’. Several case histories illustrate the scope and potential of this concept.	May 2009
NONE-No attached Diamond beamline	Microbial manufacture of chalcogenide-based nanoparticles via the reduction of selenite using Veillonella atypica: an in situ EXAFS study Carolyn I. Pearce , Victoria S. Coker , John M. Charnock , Richard A. D. Pattrick , J. Frederick W. Mosselmans , Nicholas Law , Terry J. Beveridge , Jonathan R. Lloyd Nanotechnology 19 (15), 155603 DOI: 10.1088/0957-4484/19/15/155603 Show Abstract ▼ Abstract: The ability of metal-reducing bacteria to produce nanoparticles, and their precursors, can be harnessed for the biological manufacture of fluorescent, semiconducting nanomaterials. The anaerobic bacterium Veillonella atypica can reduce selenium oxyanions to form nanospheres of elemental selenium. These selenium nanospheres are then further reduced by the bacterium to form reactive selenide which could be precipitated with a suitable metal cation to produce nanoscale chalcogenide precipitates, such as zinc selenide, with optical and semiconducting properties. The whole cells used hydrogen as the electron donor for selenite reduction and an enhancement of the reduction rate was observed with the addition of a redox mediator (anthraquinone disulfonic acid). A novel synchrotron-based in situ time-resolved x-ray absorption spectroscopy technique was used, in conjunction with ion chromatography and inductively coupled plasma–atomic emission spectroscopy, to study the mechanisms and kinetics of the microbial reduction of selenite to selenide. The products of this biotransformation were also assessed using electron microscopy, energy-dispersive spectroscopy, x-ray diffraction and fluorescence spectroscopy. This process offers the potential to prepare chalcogenide-based nanocrystals, for application in optoelectronic devices and biological labelling, from more environmentally benign precursors than those used in conventional organometallic synthesis.	Apr 2008
NONE-No attached Diamond beamline	Controlled cobalt doping of magnetosomes in vivo Sarah Staniland , Wyn Williams , Andrew Harrison , Bruce Ward , Neil Telling , Gerrit Van Der Laan Nature Nanotechnology 3 (3), 158 - 162 DOI: 10.1038/nnano.2008.35 PMID: 18654488 Show Abstract ▼ Abstract: Magnetotactic bacteria biomineralize iron into magnetite (Fe3O4) nanoparticles that are surrounded by lipid vesicles. These 'magnetosomes' have considerable potential for use in bio- and nanotechnological applications because of their narrow size and shape distribution and inherent biocompatibility(1-3). The ability to tailor the magnetic properties of magnetosomes by chemical doping would greatly expand these applications(4,5); however, the controlled doping of magnetosomes has so far not been achieved. Here, we report controlled in vivo cobalt doping of magnetosomes in three strains of the bacterium Magnetospirillum. The presence of cobalt increases the coercive field of the magnetosomes-that is, the field necessary to reverse their magnetization-by 36-45%, depending on the strain and the cobalt content. With elemental analysis, X-ray absorption and magnetic circular dichroism, we estimate the cobalt content to be between 0.2 and 1.4%. These findings provide an important advance in designing biologically synthesized nanoparticles with useful highly tuned magnetic properties.	Mar 2008

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