Этиологические факторы острого илиофеморального венозного тромбоза

ТРОМБОЗ ВЕНОЗНЫЙ /ЭТИОЛКОНЕЧНОСТЬ НИЖНЯ

Оральные антикоагулянты в профилактике венозных тромбоэмболических осложнений у ожоговых больных

ТРОМБОЭМБОЛИЯАНТИКОАГУЛЯНТЫТРОМБОЗ ВЕНОЗНЫЙОЖОГИВВЕДЕНИЕ ЛЕКАРСТВ ПЕРОРАЛЬНО

Laccase-modified gold nanorods for electrocatalytic reduction of oxygen

The multicopper oxidase Trametes hirsuta laccase (ThLc) served as a bioelectrocatalyst on nanostructured cathodes. Nanostructuring was provided by gold nanorods (AuNRs), which were characterized and covalently attached to electrodes made of low-density graphite. The nanostructured electrode was the scaffold for covalent and oriented attachment of ThLc. The bioelectrocatalytic currents measured for oxygen reductionwere as high as 0.5 mA/cm2 and 0.7 mA/cm2, which were recorded under direct and mediated electron transfer regimes, respectively. The experimental data were fitted to mathematical models showing that when the O2 is bioelectroreduced at high rotation speed of the electrode the heterogeneous electron transfer step is the rateliming stage. The electrochemical measurement hints a wider population of non-optimally wired laccases than previously reported for 5-8 nmsize Au nanoparticle-modified electrode, which could be due to a larger size of the AuNRs when compared to the laccases as well as their different crystal facets. © 2015 Elsevier B.V.This work was funded by the Seventh Framework Programme (BIOENERGY FP7-PEOPLE-2013-607793 project).Peer Reviewe

Redox potentials of the blue copper sites of bilirubin oxidases

AbstractThe redox potentials of the multicopper redox enzyme bilirubin oxidase (BOD) from two organisms were determined by mediated and direct spectroelectrochemistry. The potential of the T1 site of BOD from the fungus Myrothecium verrucaria was close to 670 mV, whereas that from Trachyderma tsunodae was >650 mV vs. NHE. For the first time, direct electron transfer was observed between gold electrodes and BODs. The redox potentials of the T2 sites of both BODs were near 390 mV vs. NHE, consistent with previous finding for laccase and suggesting that the redox potentials of the T2 copper sites of most blue multicopper oxidases are similar, about 400 mV

Activity of lactoperoxidase when adsorbed on protein layers

Lactoperoxidase (LPO) is an enzyme, which is used as an antimicrobial agent in a number of applications, e.g., food technology. In the majority of applications LPO is added to a homogeneous product phase or immobilised on product surface. In the latter case, however, the measurements of LPO activity are seldom reported. In this paperwe have assessed LPO enzymatic activity on bare and protein modified gold surfaces by means of electrochemistry. It was found that LPO rapidly adsorbs to bare gold surfaces resulting in an amount of LPO adsorbed of 2.9mg/m2. A lower amount of adsorbed LPO is obtained if the gold surface is exposed to bovine serum albumin, bovine or human mucin prior to LPO adsorption. The enzymatic activity of the adsorbed enzyme is in general preserved at the experimental conditions and varies only moderately when comparing bare gold and gold surface pretreated with the selected proteins. The measurement of LPO specific activity, however, indicate that it is about 1.5 times higher if LPO is adsorbed on gold surfaces containing a small amount of preadsorbed mucin in comparison to the LPO directly adsorbed on bare gold

On the Possibility of Uphill Intramolecular Electron Transfer in Multicopper Oxidases: Electrochemical and Quantum Chemical Study of Bilirubin Oxidase

The catalytic cycle of multicopper oxidases (MCOs) involves intramolecular electron transfer (IET) from the Cu-T1 copper ion, which is the primary site of the one-electron oxidations of the substrate, to the trinuclear copper cluster (TNC), which is the site of the four-electron reduction of dioxygen to water. In this study we report a detailed characterization of the kinetic and electrochemical properties of bilirubin oxidase (BOx) a member of the MCO family. The experimental results strongly indicate that under certain conditions, e.g. in alkaline solutions, the IET can be the rate-limiting step in the BOx catalytic cycle. The data also suggest that one of the catalytically relevant intermediates (most likely characterized by an intermediate oxidation state of the TNC) formed during the catalytic cycle of BOx has a redox potential close to 0.4 V, indicating an uphill IET process from the T1 copper site (0.7 V) to the Cu-T23. These suggestions are supported by calculations of the IET rate, based on the experimentally observed Gibbs free energy change and theoretical estimates of reorganization energy obtained by combined quantum and molecular mechanical (QM/MM) calculations

An amperometric biosensor based on laccase immobilized in polymer matrices for determining phenolic compounds

An amperometric enzyme electrode based on laccase for determining phenolic compounds is proposed. The following three types of polymer materials were used for enzyme immobilization on the surface of a glassy-carbon electrode: positively charged cetyl ethyl poly (ethyleneimine) (CEPEI) and negatively charged commercial Nafion and Eastman AQ 29D polymers. The advantages and disadvantages of each of the above polymers for enzyme immobilization are discussed. The detection limits of the model phenolic compounds hydroquinone and pyrocatechol in a buffer solution on laccase immobilization in a Nation membrane were 3.5 x 10(-8) and 5.0 x 10(-8) M, respectively, at a signal-to-noise ratio of 3. Electrodes with laccase immobilized in Nation and Eastman AQ 29D membranes exhibited the shortest response time. The operating stability and the stability in storage can be significantly improved by the additional incorporation of gelatin in the polymer matrices. Gelatin prevents enzyme inactivation as a result of enzyme modification by the free-radical oxidation products of phenolic compounds

Transparent and flexible, nanostructured and mediatorless glucose/oxygen enzymatic fuel cells

Here we detail transparent, flexible, nanostructured, membrane-less and mediator-free glucose/oxygen enzymatic fuel cells, which can be reproducibly fabricated with industrial scale throughput. The electrodes were built on a biocompatible flexible polymer, while nanoimprint lithography was used for their nanostructuring. The electrodes were covered with gold, their surfaces were visualised using scanning electron and atomic force microscopies, and they were also studied spectrophotometrically and electrochemically. The enzymatic fuel cells were fabricated following our previous reports on membrane-less and mediator-free biodevices in which cellobiose dehydrogenase and bilirubin oxidase were used as anodic and cathodic biocatalysts, respectively. The following average characteristics of transparent and flexible biodevices operating in glucose and chloride containing neutral buffers were registered: 0.63 V open-circuit voltage, and 0.6 mu W cm(-2) maximal power density at a cell voltage of 0.35 V. A transparent and flexible enzymatic fuel cell could still deliver at least 0.5 mu W cm(-2) after 12 h of continuous operation. Thus, such biodevices can potentially be used as self-powered biosensors or electric power sources for smart electronic contact lenses. (C) 2015 Elsevier B.V. All rights reserved

Biofuel cell based on microscale nanostructured electrodes with inductive coupling to rat brain neurons.

Miniature, self-contained biodevices powered by biofuel cells may enable a new generation of implantable, wireless, minimally invasive neural interfaces for neurophysiological in vivo studies and for clinical applications. Here we report on the fabrication of a direct electron transfer based glucose/oxygen enzymatic fuel cell (EFC) from genuinely three-dimensional (3D) nanostructured microscale gold electrodes, modified with suitable biocatalysts. We show that the process underlying the simple fabrication method of 3D nanostructured electrodes is based on an electrochemically driven transformation of physically deposited gold nanoparticles. We experimentally demonstrate that mediator-, cofactor-, and membrane-less EFCs do operate in cerebrospinal fluid and in the brain of a rat, producing amounts of electrical power sufficient to drive a self-contained biodevice, viz. 7 μW cm(-2) in vitro and 2 μW cm(-2) in vivo at an operating voltage of 0.4 V. Last but not least, we also demonstrate an inductive coupling between 3D nanobioelectrodes and living neurons

Mercury pollution for marine environment at Farwa Island, Libya

Coimmobilization of pyranose dehydrogenase as an enzyme catalyst, osmium redox polymers [Os­(4,4′-dimethoxy-2,2′-bipyridine)₂(poly­(vinylimidazole))₁₀Cl]⁺ or [Os­(4,4′-dimethyl-2,2′-bipyridine)₂(poly­(vinylimidazole))₁₀Cl]⁺ as mediators, and carbon nanotube conductive scaffolds in films on graphite electrodes provides enzyme electrodes for glucose oxidation. The recombinant enzyme and a deglycosylated form, both expressed in Pichia pastoris, are investigated and compared as biocatalysts for glucose oxidation using flow injection amperometry and voltammetry. In the presence of 5 mM glucose in phosphate-buffered saline (PBS) (50 mM phosphate buffer solution, pH 7.4, with 150 mM NaCl), higher glucose oxidation current densities, 0.41 mA cm^–2, are obtained from enzyme electrodes containing the deglycosylated form of the enzyme. The optimized glucose-oxidizing anode, prepared using deglycosylated enzyme coimmobilized with [Os­(4,4′-dimethyl-2,2′-bipyridine)₂(poly­(vinylimidazole))₁₀Cl]⁺ and carbon nanotubes, was coupled with an oxygen-reducing bilirubin oxidase on gold nanoparticle dispersed on gold electrode as a biocathode to provide a membraneless fully enzymatic fuel cell. A maximum power density of 275 μW cm^–2 is obtained in 5 mM glucose in PBS, the highest to date under these conditions, providing sufficient power to enable wireless transmission of a signal to a data logger. When tested in whole human blood and unstimulated human saliva maximum power densities of 73 and 6 μW cm^–2 are obtained for the same fuel cell configuration, respectively