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41.
Scanlon MD Salaj-Kosla U Belochapkine S MacAodha D Leech D Ding Y Magner E 《Langmuir : the ACS journal of surfaces and colloids》2012,28(4):2251-2261
The high surface areas of nanostructured electrodes can provide for significantly enhanced surface loadings of electroactive materials. The fabrication and characterization of nanoporous gold (np-Au) substrates as electrodes for bioelectrochemical applications is described. Robust np-Au electrodes were prepared by sputtering a gold-silver alloy onto a glass support and subsequent dealloying of the silver component. Alloy layers were prepared with either a uniform or nonuniform distribution of silver and, post dealloying, showed clear differences in morphology on characterization with scanning electron microscopy. Redox reactions under kinetic control, in particular measurement of the charge required to strip a gold oxide layer, provided the most accurate measurements of the total electrochemically addressable electrode surface area, A(real). Values of A(real) up to 28 times that of the geometric electrode surface area, A(geo), were obtained. For diffusion-controlled reactions, overlapping diffusion zones between adjacent nanopores established limiting semi-infinite linear diffusion fields where the maximum current density was dependent on A(geo). The importance of measuring the surface area available for the immobilization was determined using the redox protein, cyt c. The area accessible to modification by a biological macromolecule, A(macro), such as cyt c was reduced by up to 40% compared to A(real), demonstrating that the confines of some nanopores were inaccessible to large macromolecules due to steric hindrances. Preliminary studies on the preparation of np-Au electrodes modified with osmium redox polymer hydrogels and Myrothecium verrucaria bilirubin oxidase (MvBOD) as a biocathode were performed; current densities of 500 μA cm(-2) were obtained in unstirred solutions. 相似文献
42.
Highly ordered macroporous electrodes are prepared by electro-deposition of gold through a polystyrene sphere template. Drop-coating redox polymer and either glucose oxidase, for the anode, or Melanocarpus albomyces laccase, for the cathode on the macroporous gold provides film-coated electrodes for assembly of membrane-less glucose/oxygen enzymatic fuel cells (EFC) in pH 7.4 buffer containing 10 mM glucose and 0.15 M NaCl. Under these conditions the maximum power density of 17 μW cm(-2) for EFCs using films adsorbed to planar gold electrodes increased to 38 μW cm(-2) for films adsorbed to 2? sphere gold macroporous electrodes. 相似文献
43.
Stewart F. Parker Keith Refson Susan M. Tavender Peter Albers Bernd Hannebauer Matthias Janik Arndt Müller Jürgen Martens Martin Watzke Kenneth Shankland Charlotte Leech Heribert Offermanns 《Journal of Raman spectroscopy : JRS》2009,40(6):703-708
The product of the Asinger reaction between elemental sulfur, n‐butylamine and acetophenone is 8‐(n‐butylaminophenylmethyliden)‐1,2,3,4,5,6,7‐heptathiocane which contains a CS7 ring. A combination of infrared, Raman and inelastic neutron scattering spectroscopies with periodic density functional theory calculations is used to provide a complete assignment of the vibrational spectra of this unusual species. The similarity between the Raman spectra of the compound and that of elemental sulfur is particularly striking. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
44.
Cara L Ryan David C Baranowski Babykumari P Chitramuthu Suneil Malik Zhi Li Mingju Cao Sandra Minotti Heather D Durham Denis G Kay Christopher A Shaw Hugh PJ Bennett Andrew Bateman 《BMC neuroscience》2009,10(1):1-22
Background
Progranulin is a secreted high molecular weight growth factor bearing seven and one half copies of the cysteine-rich granulin-epithelin motif. While inappropriate over-expression of the progranulin gene has been associated with many cancers, haploinsufficiency leads to atrophy of the frontotemporal lobes and development of a form of dementia (frontotemporal lobar degeneration with ubiquitin positive inclusions, FTLD-U) associated with the formation of ubiquitinated inclusions. Recent reports indicate that progranulin has neurotrophic effects, which, if confirmed would make progranulin the only neuroprotective growth factor that has been associated genetically with a neurological disease in humans. Preliminary studies indicated high progranulin gene expression in spinal cord motor neurons. However, it is uncertain what the role of Progranulin is in normal or diseased motor neuron function. We have investigated progranulin gene expression and subcellular localization in cultured mouse embryonic motor neurons and examined the effect of progranulin over-expression and knockdown in the NSC-34 immortalized motor neuron cell line upon proliferation and survival.Results
In situ hybridisation and immunohistochemical techniques revealed that the progranulin gene is highly expressed by motor neurons within the mouse spinal cord and in primary cultures of dissociated mouse embryonic spinal cord-dorsal root ganglia. Confocal microscopy coupled to immunocytochemistry together with the use of a progranulin-green fluorescent protein fusion construct revealed progranulin to be located within compartments of the secretory pathway including the Golgi apparatus. Stable transfection of the human progranulin gene into the NSC-34 motor neuron cell line stimulates the appearance of dendritic structures and provides sufficient trophic stimulus to survive serum deprivation for long periods (up to two months). This is mediated at least in part through an anti-apoptotic mechanism. Control cells, while expressing basal levels of progranulin do not survive in serum free conditions. Knockdown of progranulin expression using shRNA technology further reduced cell survival.Conclusion
Neurons are among the most long-lived cells in the body and are subject to low levels of toxic challenges throughout life. We have demonstrated that progranulin is abundantly expressed in motor neurons and is cytoprotective over prolonged periods when over-expressed in a neuronal cell line. This work highlights the importance of progranulin as neuroprotective growth factor and may represent a therapeutic target for neurodegenerative diseases including motor neuron disease. 相似文献45.
A simple, rapid, reproducible and effective one-step procedure for biosensor construction, based on casting mixed poly(ester-sulfonic acid)-glucose oxidase solutions onto solid electrodes is described. The cation exchanger simultaneously performs the entrapment, charge permselectivity and antifouling functions. The discrimination against potential interferences is accompanied with a fast and sensitive response to glucose. With flow injection operation, 180 samples can be processed per hour, with a detection limit of 3 × 10?6 M. The effects of numerous experimental variables are explored. These properties of poly(ester-sulfonic acid) ionomers, coupled with their availability as aqueous dispersions, make them attractive and versatile for biosensor work. 相似文献
46.
Dennis Leech 《Annals of Operations Research》2002,109(1-4):375-397
In general in an organisation whose system of governance involves weighted voting, a member's weight in terms of the number of votes and the formal power it represents differ. Power indices provide a means of analysing this difference. The paper uses new algorithms for computing power indices for large games. Three analyses are carried out: (1) the distribution of Banzhaf voting power among members in 1999; the results show that the United States has considerably more power over ordinary decisions than its weight of 17% but that the use of special supermajorities limits its power; (2) the effect of varying the majority requirement on the power of the IMF to act and the powers of members to prevent and initiate action (Coleman indices); the results show the effect of supermajorities severely limits the power to act and therefore renders the voting system ineffective in democratic terms, also the sovereignty of the United States within the IMF is effectively limited to just the power of veto; (3) the paper proposes the determination of the weights instrumentally by means of an iterative algorithm to give the required power distribution; this would be a useful procedure for determining appropriate changes in weights consequent on changes to individual countries' quotas; this is applied to the 1999 data. Policy recommendations are, first, that the IMF use only simple majority voting, and discontinue using special supermajorities, and, second, allocate voting weight instrumentally using power indices. 相似文献
47.
48.
Transfer to benzoyl peroxide is pronounced in the polymerization of p-methoxystyrene (MOS) at 60°. The process is responsible for the low molecular weights of polymers formed when the peroxide is used as initiator; there is no evidence for a non-radical polymerization of the type found with N-vinylcarbazole and the peroxide. Data on the reactivity of MOS towards the benzoyloxy radical and the copolymerization of MOS with methyl methacrylate are presented. 相似文献
49.
Electrically ‘wired’ tyrosinase enzyme inhibition electrode for the detection of respiratory poisons
The use of the solution redox species, [Os(bpy)2Cl2]+/0, [Os(bpy)2(MeIm)Cl]2+/+ and [Fe(CN)6]4−/3−, where bpy is 2,2-bipyridine and MeIm is N-methylimidazole, as electron mediators in the enzymatic reduction of oxygen by tyrosinase is investigated. Co-immobilization of both enzyme and an osmium redox mediator in a hydrogel on glassy carbon electrodes results in a biosensor for the ‘reagentless’ addressing of enzyme activity, consuming only oxygen present in solution. Immobilized enzyme inhibition biosensors can thus be constructed for the detection of tyrosinase inhibitors, such as sodium azide, using this approach. The enzyme inhibition biosensor can detect levels of azide as low as 5 × 10−6 mol dm−3 in solution and may be useful in environmental monitoring applications and as an early warning poison sensor. 相似文献
50.
Davies SG Haggitt JR Ichihara O Kelly RJ Leech MA Price Mortimer AJ Roberts PM Smith AD 《Organic & biomolecular chemistry》2004,2(18):2630-2649
Diastereoselective conjugate addition of homochiral lithium (R)-N-allyl-N-alpha-methylbenzylamide to methyl (2E,5E)-hepatadienoate, followed by protecting group manipulation and subsequent iodocyclocarbamation allows a concise route to the core fragment, methyl (3R,5R,6R)-3,6-diamino-5-hydroxyheptanoate, of sperabillins B and D. Differentiation between the C-3 and C-6 primary amino groups of this core amino acid was readily achieved by treatment with acetone, giving the 5,6-isopropylidene and C-3-imine protected diamine, with subsequent regioselective acylation of the C-6-nitrogen facilitating the total synthesis of sperabillin D in 10.8% overall yield, and the first asymmetric synthesis of sperabillin B in 5.8% overall yield. 相似文献