Multilayer structured carbon nanotubes/poly-L-lysine/laccase composite cathode for glucose/O-2 biofuel cell

Multilayer film of laccase, poly-L-lysine (PLL) and multi-walled carbon nanotubes (MWNTs) were prepared by a layer-by-layer self-assembly technique. The results of the UV-vis spectroscopy and scanning electron microscopy studies demonstrated a uniform growth of the multilayer. The catalytic behavior of the modified electrode was investigated. The (MWNTs/PLL/laccase)(n) multilayer modified electrode catalyzed four-electron reduction of O-2 to water, without any mediator.

Highly ordered mesoporous carbons-based glucose/O-2 biofuel cell

This study demonstrates a novel compartment-less glucose/O-2 biofuel cell (BFC) based on highly ordered mesoporous carbons (OMCs) with three-dimensionally (3D) interconnected and ordered pore structures. OMCs are used as supports for both stably confining the electrocatalyst (i.e., meldola's blue, MDB) for NADH oxidation and the anodic biocatalyst (i.e., NAD(+)-dependent glucose dehydrogenase, GDH) for glucose oxidation, and for facilitating direct electrochemistry of the cathodic biocatalyst (i.e., laccase, LAC) for O-2 electroreduction. In 0.10 M pH 6.0 PBS containing 20 mM NAD(+) and 60 mM glucose under the air-saturated atmosphere, the open circuit voltage (0.82 V) and the maximum power output (38.7 mu W cm(-2) (at 0.54V)) of the assembled compartment-less OMCs-based BFC are both higher than those of carbon nanotubes (CNTs)-based BFC (0.75 V and 2.1 mu W cm(-2) (at 0.46 V)).

迟缓爱德华氏菌(Edwardsiella tarda) LuxS/AI-2群体感应系统研究

从患病牙鲆中分离出迟缓爱德华氏菌株TX1，经报告菌株检测发现TX1有AI-2活性。用梯度PCR和Genome walking的方法克隆了TX1 luxS基因，将luxS基因在大肠杆菌DH5α中表达，证明其具有功能活性。在TX1中，luxS的表达与AI-2的活性基本是一致的，二者均受生长时期和生长条件的调节，即在glucose存在的条件下luxS表达和AI-2活性升高，而在高温条件下luxS表达和AI-2活性降低。glucose对AI-2活性以及luxS表达的影响经过荧光定量PCR，启动子活性检测，AI-2活性检测以及凝胶滞缓等一系列的实验证实是由cAMP-CRP复合物介导的，该复合物可以通过与luxS启动子相互作用而抑制luxS的表达。RNA干扰表明，TX1中luxS表达被干扰以后，对细菌产生了多方面的影响，包括：(1) 降低AI-2水平；(2) 降低细菌的生长能力；(3) 降低Ⅲ型分泌系统相关基因的表达水平以及生物膜的形成能力；(4) 减弱细菌毒力。外源AI-2的添加可以回复Ⅲ型分泌系统相关基因的表达水平以及生物膜的形成，但是并不能修复生长状况，表明LuxS在TX1中具有双重功能，即参与细胞代谢以及群体感应信号传导。基于LuxS/AI-2群体感应系统对细菌毒力的重要性，设计并筛选了一个该系统的阻遏因子5411。Pull-down实验证明5411可以和LuxS特异性结合。研究表明5411在TX1中表达导致细菌毒力显著下降。将5411克隆至牙鲆共生菌FP3中，发现5411可以被分泌到胞外并能被TX1吸收。将表达5411的共生菌导入牙鲆，发现其能够有效阻遏TX1对牙鲆的侵染。 这些结果表明：(1) TX1中AI-2的活性受控于LuxS，而后者则受生长时期和生长条件的调控；(2) luxS的正常表达对于细菌的正常生长和侵染是必需的；(3) LuxS/AI-2群体感应系统调控Ⅲ型分泌系统相关毒力因子的表达；(4) 通过阻遏LuxS/AI-2群体感应系统来抑制病原菌侵染是一种具有潜力的新型病害防控方法。

Extracellular carbohydrate polymers from five desert soil algae with different cohesion in the stabilization of fine sand grain

Extracellular polymeric substances (EPS) from four filamentous cyanobacteria Microcoleus vaginatus, Scytonema javanicum, Phormidium tenue and Nostoc sp. and a coccoid single-cell green alga Desmococcus olivaceus that had been separated from desert algal crusts of Tegger desert of China, were investigated for their chemical composition, structure,and physical properties. The EPS contained 7.5-50.3% protein (in polymers ranging from 14 to more than 200 kD, SDS-PAGE) and 16.2-46.5% carbohydrate (110-460 kD, GFC). 6-12 kinds of monosaccharides, including 2-O-methyl rhamnose, 2-O-methyl glucose, and N-acetyl glucosamine were found. The main carbohydrate chains from M. vaginatus and S. javanicum consisted mainly of equal proportion of Man, Gal and Glc, that from P. tenue consisted mainly of arabinose, glucose and rhamnose. Arabinose was present in pyranose form, mainly alpha-L 1 --> 3 linked, with branches on C4 of almost half of the units. Glucose was responsible for the terminal units, in addition of having some units as beta1 --> 3 and some as beta1 --> 4 linked. Rhamnose was mainly 1 --> 3 linked with branches on C2 on half of the units. The carbohydrate polymer from D. olivaceus was composed mainly of beta1 --> 4 linked xylose, galactose and glucose. The galactose part was present both in beta-pyranose and -furanose forms. Arabinose in alpha-L-furanose form was mainly present as 1 --> 2 and 1 --> 2, 5 linked units, rhamnose only as alpha 1 --> 3 and xylose as beta 1 --> 4. The backbone of the polysaccharide from Nostoc sp. was composed of beta-1 --> 4 linked xylose, galactose and glucose. Most of the glucose was branched on position C6, terminal glucose and 2-O-methyl glucose units are also present. The relationship between structure, physical properties and potential biological function is discussed. (C) 2003 Elsevier Ltd. All rights reserved.

A biofuel cell with enhanced performance by multilayer biocatalyst immobilized on highly ordered macroporous electrode

A one-compartment glucose/O-2. biofuel cell based on an electrostatic layer-by-layer (LbL) technique on three-dimensional ordered macroporous (3DOM) gold electrode was described. A 3DOM gold electrode was synthesized electrochemically by an inverted colloidal crystal template technique. Then the macroporous gold electrodes were functionalized with Au nanoparticles (AuNPs) and enzyme, glucose dehydrogenase (GDH) or laccase.

Effects of temperature, glucose and inorganic nitrogen inputs on carbon mineralization in a Tibetan alpine meadow soil

High levels of available nitrogen (N) and carbon (C) have the potential to increase soil N and C mineralization We hypothesized that with an external labile C or N supply alpine meadow soil will have a significantly higher C mineralization potential and that temperature sensitivity of C mineralization will increase To test the hypotheses an incubation experiment was conducted with two doses of N or C supply at temperature of 5 15 and 25 C Results showed external N supply had no significant effect on CO2 emission However external C supply increased CO2 emission Temperature coefficient (Q(10)) ranged from 113 to 1 29 Significantly higher values were measured with C than with N addition and control treatment Temperature dependence of C mineralization was well-represented by exponential functions Under the control CO2 efflux rate was 425 g CO2-Cm-2 year(-1) comparable to the in situ measurement of 422 g CO2-Cm-2 year(-1) We demonstrated if N is disregarded microbial decomposition is primarily limited by lack of labile C It is predicted that labile C supply would further increase CO2 efflux from the alpine meadow soil (C) 2010 Elsevier Masson SAS All rights reserved

Fe3O4 magnetic nanoparticles as peroxidase mimetics and their applications in H2O2 and glucose detection

Artificial enzyme mimetics are a current research interest because natural enzymes bear some serious disadvantages, such as their catalytic activity can be easily inhibited and they can be digested by proteases. A very recently study reported by Yan et al. has proven that Fe3O4 magnetic nanoparticles (MNPs) exhibit an intrinsic enzyme mimetic activity similar to that found in natural peroxidases, though MNPs are usually thought to be biological and chemical inert (Gao, L. Z.; Zhuang, J.; Nie, L.; Zhang, J. B.; Zhang, Y.; Gu, N.; Wang, T. H.; Feng, J.; Yang, D. L.; Perrett, S.; Yan, X. Y. Nat. Nanotechnol. 2007, 2, 577-583).

Carbon nanotube/gold nanoparticles/polyethylenimine-functionalized ionic liquid thin film composites for glucose biosensing

A novel glucose biosensor based on immobilization of glucose oxidase (GOD) in thin films of polyethylenimine-functionalized ionic liquid (PFIL), containing a mixture of carbon nanotubes (CNT) and gold nanoparticles (AuNPs) and deposited on glassy carbon electrodes, was developed. Direct electrochemistry of glucose oxidase in the film was observed, with linear glucose response up to 12 mM. The PFIL-stabilized gold nanoparticles had a diameter of 2.4 +/- 0.8 nm and exhibited favorable stability (stored even over one month with invisible change in UV-vis spectroscopic measurements).

Nonenzymatic glucose sensor based on renewable electrospun Ni nanoparticle-loaded carbon nanofiber paste electrode

A novel nonenzymatic glucose sensor was developed based on the renewable Ni nanoparticle-loaded carbon nanofiber paste (NiCFP) electrode. The NiCF nanocomposite was prepared by combination of electrospinning technique with thermal treatment method. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images showed that large amounts of spherical nanoparticles were well dispersed on the surface or embedded in the carbon nanofibers. And the nanoparticles were composed of Ni and NiO, as revealed by energy dispersive X-ray spectroscopy (EDX) and X-ray powder diffraction (XRD). In application to nonenzymatic glucose determination, the renewable NiCFP electrodes, which were constructed by simply mixing the electrospun nanocomposite with mineral oil, exhibited strong and fast amperometric response without being poisoned by chloride ions. Low detection limit of 1 mu M with wide linear range from 2 mu M to 2.5 mM (R = 0.9997) could be obtained.

Direct Electrochemistry of Glucose Oxidase and Biosensing for Glucose Based on Graphene

We first reported that polyvinylpyrrolidone-protected graphene was dispersed well in water and had good electrochemical reduction toward O-2 and H2O2. With glucose oxidase (GOD) as an enzyme model, we constructed a novel polyvinylpyrrolidone-proteeted graphene/polyethylenimine-ftmctionalized ionic liquid/GOD electrochemical biosensor, which achieved the direct electron transfer of GOD, maintained its bioactivity and showed potential application for the fabrication of novel glucose biosensors with linear glucose response up to 14 mM.

A biofuel cell harvesting energy from glucose-air and fruit juice-air

The membraneless biofuel cell (BFC) is facile prepared based on glucose oxidase and laccase as anodic and cathodic catalyst, respectively, by using 1,1'-dicarboxyferrocene as the mediators of both anode and cathode. The BFC can work by taking glucose as fuel in air-saturated solution, in which air serves as the oxidizer of the cathode. More interestingly, the fruit juice containing glucose, e.g. grape, banana or orange juice as the fuels substituting for glucose can make the BFC work. The BFC shows several advantages which have not been reported to our knowledge: (1) it is membraneless BFC which can work with same mediator on both anode and cathode; (2) fruit juice can act as fuels of BFCs substituting for usually used glucose; (3) especially, the orange juice can greatly enhance the power output rather than that of glucose, grape or banana juice. Besides, the facile and simple preparation procedure and easy accessibility of fruit juice as well as air being whenever and everywhere imply that our system has promising potential for the development and practical application of BFCs.

Molecular "Wiring" glucose oxidase in supramolecular architecture

Supramolecular organized multilayers were constructed by multiwalled carbon nanotubes modified with ferrocene-derivatized poly(allylamine) redox polymer and glucose oxidase by electrostatic self-assembly. From the analysis of voltammetric signals and fluorescence results, a linear increment of the coverage of enzyme per bilayer was estimated, which demonstrated that the multilayer is constructed in a spatially ordered manner. The cyclic voltammograms obtained from the indium tin oxide (ITO) electrodes coated by the (Fc-PAH@CNT/GOx)(n) multilayers revealed that bioelectrocatalytic response is directly correlated to the number of deposited bilayers; that is, the sensitivity is tunable by controlling the number of bilayers associated with ITO electrodes. The incorporation of redox-polymer-functionalized carbon nanotubes (CNT) into enzyme films resulted in a 6-10-fold increase in the glucose electrocatalytic current; the bimolecular rate constant of FADH(2) oxidation (wiring efficiency) was increased up to 12-fold. Impedance spectroscopy data have yielded the electron diffusion coefficient (D-e) of this nanostructure to be over 10(-8) cm(2) s(-1), which is typically higher than those systems without CNT by at least a factor of 10, indicating that electron transport in the new supramolecular architecture was enhanced by communication of the redox active site of enzyme, redox polymer, and CNT.

Electrochemistry of glucose oxidase immobilized on the carbon nanotube wrapped by polyelectrolyte

A more stably dispersing of multi-wall carbon nanotube composite (noted as PDDA-MWNT), which was obtained by wrapping the MWNT with poly (diallydimethylammonium) chloride (PDDA), was used for the immobilization of glucose oxidase (GOD) and its bioelectrochemical studies. The morphologies and structures of the PDDA-MWNT composite were characterized by environment-canning electron microscopy (ESEM) and X-ray photoelectron spectroscopy (XPS). Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry were used to feature the GOD adsorbed onto the electrode modified by PDDA-MWNT composite. The immobilized GOD at the PDDA-MWNT films exhibited a pair of well-defined nearly reversible redox peaks and a fast heterogeneous electron transfer rate with the rate constant (k(s)) of 2.76 s(-1). In addition, GOD immobilized in this way retained its bioelectrocatalytic activity for the oxidation of glucose. The method of immobilizing GOD without any additional cross-linking agents presented here is easy and facile, which provides a model for other redox enzymes and proteins.