bluuebunny/crossref_metadata_2025_split huggingface dataset:
Microdialysis fiber enzyme electrode involving amplification by substrate recycling
Authors: Yao Toshio , Suzuki Seita , Nishino Hirohito , Nakahara Taketoshi 
Published: May 2005

AbstractA microdialysis fiber electrode involving amplification for the NAD+/NADH couple is described. The electrode contains glucose‐6‐phosphate dehydrogenase, lactate dehydrogenase and lactate oxidase held stationary within its cavity, with a platinum fiber coated with poly(1,2‐diaminobenzene) film as a working electrode and a silver/silver chloride fiber as a reference electrode. Both NAD+ and NADH are recycled enzymatically in the presence of an excess of glucose‐6‐phosphate and pyruvate in the measuring buffer solution. As a result, a large amount of L‐lactate produced in the electrode cavity is converted to pyruvate to produce hydrogen peroxide, which can be detected ampero metrically at the platinum fiber with a size‐exclusion film. Both NAD+ and NADH were detected with a 25‐fold increase in sensitivity compared with the unamplified responses. The detection limit was 1 × 10−7 M.
Acetylcholine minisensor based on metal‐supported lipid bilayers for determination of environmental pollutants
Authors: Rehák M. , Šnejdárková M. , Hianik T. 
Published: May 2005

AbstractImmobilization of avidin‐modified acetylcholinesterase and choline oxidase (A‐COxACE) on a metal supported biotinylated membrane allowed us to developed a minisensor based on changes in anticholinesterase activity by several environmental pollutants. The concentrations of acetylcholine and choline have been determined amperometrically on the basis of anodic oxidation of hydrogen peroxide, a product of choline oxidase. The immobilization of the complex A COxACE was controlled by the electrostriction method which allowus to determine changes of membrane capacitance C and elasticity modulus E⟂ in a direction perpendicular to the s‐BLM surface. The binding of the A‐COxACE complex to s‐BLM resulted in a decrease of C and in an increase of E⟂ suggesting increase in the membrane ordering. Using the simple amperometric method we were able to use this minisensor for detection of acetylcholine and choline. Detection limits were 0.79 mM and 1.25 mM for acetylcholine and choline, respectively. The biosensor was tested for acetylcholinesterase inhibition in the presence of organophosphorus Trichlorphon and eserine.
Electrochemical behavior of H2O2 on gold
Authors: Gerlache Marc , Senturk ZÜHre , Quarin Guy , Kauffmann Jean‐Michel 
Published: May 2005

AbstractCyclic voltammetric studies of hydrogen peroxide on a polycrystalline gold electrode have permitted to point out that the oxidation of the molecule may occur at two distinct potentials depending on the sample composition and cleanliness and on the redox state of the electrode. At a clean gold surface, the oxidation of hydrogen peroxide gives only one wave at +490 mV (vs. Ag/AgCl) at pH 7.4, besides the gold oxidation wave at +820 mV. Species in solution which adsorb readily on gold (trace impurities originating because of sonication or solution stirring), gold oxide and acidic pH values, inhibit this wave and oxidation of hydrogen peroxide is occurring at a higher potential, i.e., +870 mV in phosphate buffer pH 7.4. Cyclic voltammograms show these two waves, depending on the degree of inhibition of hydrogen peroxide. At oxidized gold electrodes or contaminated by surface active species, oxidation of hydrogen peroxide gives only one wave at +870 mV. From these data it may be inferred that hydroxy species adsorbed on clean gold favor the formation of the first wave. Both waves may be advantageously exploited for quantitative purpose. The latter is not affected by surface active species and permits quantification of hydrogen peroxide down to 20 μM with a detection limit of 4 μM.
β‐cyclodextrin and carboxymethylated β‐cyclodextrin polymer film modified electrodes, hosting cobalt porphyrins, as sensors for electrocatalytic determination of oxygen dissolved in solution
Authors: D'Souza Francis , Hsieh Yi‐Ying , Wickman Heang , Kutner Wlodzimierz 
Published: May 2005

AbstractNew oxygen sensors, based on polymer film modified electrodes, were prepared and applied for electrocatalytic determination of dioxygen dissolved both in aqueous and aqueous‐organic, mixed solvent solutions. The sensors were made of gold electrodes coated with thin polymer film matrices of either neutral β‐cyclodextrin polymer, β‐CDP, or cation‐exchange carboxymethylated β‐cyclodextrin polymer, β‐CDPA, hosting electrocatalytically active centes of cobalt tetraphenylporphyrin, (TPP)Co, cobalt tetrakis‐(N‐methylpyridyl)porphyrin, (TMPyP)Co, or cobalt tetrakis‐(4‐sulfonatophenyl)porphyrin, (TPPS)Co. Films were cast from aqueous solutions of the respective β‐cyclodextrin prepolymer, cobalt porphyrin and glutaric dialdehyde used as the polycondensation crosslinking reagent. Catalytic dioxygen electroreduction at the electrode coated with polymer film hosting the cobalt porphyrin catalyst involves two electrons and two protons resulting in the formation of hydrogen peroxide. The sensitivity of dioxygen determination largely increases in the order (TPPS)Co <(TPP)Co<(TMPyP) Co for the β‐CDPA film electrodes, being governed by ion‐exchange equilibria with respect to the cobalt porphyrin catalyst, while it depends only slightly on the nature of the cobalt porphyrin catalyst for the β‐CDP film. The catalytic rate constant of the dioxygen reaction with the cobalt porphyrin catalyst in the film was estimated as k ≈︁ 2 × 104 M−1 s−1 being larger than those for either adsorbed or electropolymerized catalyst at the electrode and close to that for the catalyst present in solution. The performance of the sensors is presented with respect to the detection signal linearity, reproducibility, long‐term stability, reversibility regarding dioxygen binding and response time.
Hydrocarbon pasting liquids for improved tyrosinase‐based carbon‐paste phenol biosensors
Authors: Wang Joseph , Lu Fang , Kane Stephen A. , Choi Yong‐Kook , Smyth Malcolm R. , Rogers Kim 
Published: May 2005

AbstractShort‐chain hydrocarbons are used as pasting liquids in carbon‐paste tyrosinase amperometric biosensors. The response of the phenolic substrates decreases rapidly upon increasing the chain length of the hydrocarbon binder from C10 to C14, and then it levels off to a size similar to that of the mineral oil biosensor. For example, the dodecane‐based enzyme electrode offers a 17.8‐fold signal enhancement compared to the mineral‐oil one. Such sensitivity enhancements are attributed to the extractive accumulation of the phenolic substrates. The change in the carbon‐paste binder influences also the selectivity of the tyrosinase electrode and the Km, app values. Flow‐injection analysis yields a detection limit of 6 nM catechol and a relative standard deviation of 2.5% (n = 30). A dual enzyme electrode chromatographic detection, based on the use of different pasting liquids, provides unique characterization of the phenolic substrates. The merits of this strategy are illustrated in connection with a river water sample.
Graphite‐teflon‐peroxidase composite electrodes. Application to the direct determination of glucose in musts and wines
Authors: del Cerro Maria Antonia , Cayuela Gabriela , Reviejo A. Julio , Pingarrón Jose M. , Wang Joseph 
Published: May 2005

AbstractThe performance of graphite‐70%Teflon‐peroxidase‐ferrocene composite electrodes, fabricated by simple physical inclusion of the enzyme and the mediator into the bulk of a graphite‐Teflon matrix, by using both batch and flow‐injection modes, is reported. The electrode responds very rapidly to changes in H2O2concentration due to the absence of a membrane barrier on the electrode surface and of a covalent attachment of the enzyme to graphite. The composite enzyme electrode showed a long‐term operation due to the renewability of its surface by polishing. Reproducible amperometric responses were achieved with different electrodes fabricated from different composite matrices, and no significant loss of the enzyme activity was observed after seven months of dry‐storage at 4°C. A bienzymatic graphite‐70%Teflon‐peroxidase‐glucose oxidase‐ferrocene electrode has been developed, too, showing a rapid response to the changes in the glucose concentration. The stability of the bienzymatic composite electrode was similar to that of the peroxidase biosensor. This biosensor was applied to the determination of glucose in must and wine samples by batch amperometry and flow injection with amperometric detection modes.
Development of a sol‐gel enzyme inhibition‐based amperometric biosensor for cyanide
Authors: Park Tae‐Myung , Iwuoha Emmanuel I. , Smyth Malcolm R. 
Published: May 2005

AbstractAn amperometric sol‐gel‐based enzyme inhibition electrode for the detection of low levels of cyanice was constructed by immobilizing horseradish peroxidase (HRP) and an osmium redox polymer ([Os(bpy)2(PVP)10Cl]Cl; abbreviated Os‐polymer) as mediator. Upon addition of hydrogen peroxide to the solution, a bioelectrocatalytic reduction wave was observed, which was diffusion controlled. This reduction current is subsequently inhibited by cyanide. The steady‐state hydrogen peroxide catalytic reduction current reached a plateau at 150 mV (vs. Ag/AgCl) and cyanide could be determined amperometrically with good sensitivity at 0mV (vs. Ag/AgCl). The concentration range of linear response, apparent inhibition constant (K), and detection limit were 0.004–0.04 mM, 0.0637 mM, and 0.5 μM, respectively. Sodium azide, potassium thiocyanide and thiourea were all found not to interfere at this potential. The biosensor was found to be stable for over 1 week on storage at room temperature.
The application of cholinesterase potentiometric biosensor for preliminary screening of the toxicity of waste waters
Authors: Evtugyn G. A. , Rizaeva E. P. , Stoikova E. E. , Latipova V. Z. , Budnikov H. C. 
Published: May 2005

AbstractThe application of cholinesterase biosensor for preliminary testing of total pollution of domestic and industrial discharges has been investigated. The results indicate that biosensor‐based testing is more sensitive than paramecia bioassay. For numerous samples tested, the inhibition degree of biosensor response exceeds the appropriate value of acute toxicity on Paramecium caudatum. Electrochemical oxidation of the samples, before the biosensor testing readily removes oxidizable compounds which do not effect a real risk of environmental pollution. Simultaneous determination of inhibitory effect, acute toxicity and biochemical (chemical) oxygen demand makes it possible to infer a possible source of contamination of waters.
Ascorbate sensor based on ‘self‐doped’ polyaniline
Authors: Zhou Dong‐Mei , Xu Jing‐Juan , Chen Hong‐Yuan , Fang Hui‐Qun 
Published: May 2005

AbstractSelf‐doped polyaniline modified electrodes were successfully fabricated by copolymerization of aniline and m‐aminobenzoic acid in 0.5 mol L−1 sulfuric acid. The electrochemical characteristics of this resulting polymer were investigated. The polymer displayed electrochemical activity with the formal potential of 50 mV in pH 7.0 buffer solution. Also, such ‘self‐doped’ polyaniline was rather stable for a long‐term use. Ascorbate was electrocatalytically oxidized at these ‘self‐doped’ polymer‐modified electrodes. The effect of pH on the catalysis of ascorbate was explored. By constant potential method, such polymer was also deposited on a dual platinum disk electrode with a gap of 10 μm. The dependence of the film conductivity on the potential, which showed a peak‐shaped curve, was obtained. The device also showed a fast off‐on response sensitive to ascorbate with a linearity up to 6.0 × 10−3mol L−1 (correlation coefficient 0.996).
Correlation between the redox potentials of 9‐substituted anthracenes and the results of PM3 calculation
Authors: Okazaki Satoshi , Oyarna Munetaka , Nomura Satoshi 
Published: May 2005

AbstractThe formal redox potentials of 9‐substituted anthracenes (9XA) were measured by means of a fast scan cyclic voltammetry (FSCV) with a microelectrode. Because the FSCV depresses the influence of subsequent fast reactions, the redox potentials could be measured for a series of substituents in both the oxidation and the reduction processes. The correlation of the redox potentials with the results of molecular orbital calculations were demonstrated, in particular with the PM3 method. The plots of the redox potential versus the energy difference between the redox states gave better correlat on than those versus the energy levels of the HOMO and LUMO.
Photo‐cured ammonium and hydrogen ion selective coated‐wire electrodes used simultaneously in a portable battery‐powered flow injection analyzer
Authors: Alexander Peter W. , Dimitrakopoulos Telis , Hibbert D. Brynn 
Published: May 2005

AbstractNonactin and N,N‐dioctadecylmethylamine ionophores, each in an epoxydiacrylate polymer, were photo‐cured on silver wires (0.8 mm i.d.) and evaluated as ammonium and hydrogen (pH) coated wire electrodes. The photo‐cured membranes prepared in this study exhibited excellent adhesion to the metal substrate and improved mechanical strength compared to PVC based membranes. The ammonium electrode exhibited a Nernstian response over a concentration range between 0.01 mM and 100 mM with a detection limit of 0.0005 mM. The ammonium electrode exhibited improved selectivity against most common interfering ions, including potassium compared to previous studies. The hydrogen selective electrode exhibited a near‐Nernstian slope of 55.9 ± 0.8 mV change/log a between pH 4.0 and pH 11.0 in the steady‐state mode. The ammonium and pH sensors each responded quickly reaching 90% of steady‐state value in < 5 s, making these coated wire sensors ideal for flow injection potentiometry measurements. In the FIP mode, both the photo‐cured ammonium and pH electrodes exhibited near‐Nernstian responses of 49.2 ± 1.0 mV change/activity decade and 50.2 ± 0.4 mV change/log a, respectively, over a similar concentration range as in the steady‐state mode. The photo‐cured ammonium and pH electrodes were used simultaneously in the analysis of hydroponic nutrient solutions and waste water samples obtained from a local greenhouse grower in the flow injection potentiometric mode.
Screen‐printed voltammetric sensors for 2‐furaldehyde based on nickel‐modified and amalgam‐stabilized mercury‐coated carbon inks
Authors: Slater Jonathan M. , Dilleen John W. 
Published: May 2005

AbstractThis article describes a general method for stabilizing microdroplets of mercury on thick‐film screen printed electrodes (SPEs). Electrodes modified with nickel metal powder are compared with amalgam stabilized mercury SPEs. Application of the electrodes to the measurement of organic materials is demonstrated by the electrochemical determination of 2‐furaldehyde, a marker for power transformer condition monitoring. The electrodes were characterized by cyclic voltammetry and subsequently a square‐wave voltammetric method was used to extend the detection limit of the measurement. The resulting cathodic currents for the reduction of 2‐furaldehyde was proportional to the concentration of 2‐furaldehyde. Plots of 2‐furaldehyde concentration against response at a nickel‐modified carbon SPE gave linear regions for concentrations in the range 3.7–14.3 ppm (regression equation; Y = 0.99 + 0.15x,r = 0.999, n = 3), and linear regions at mercury‐coated silver‐modified carbon SPEs in the range 8.9–36.4 ppm (regression equation; Y = 1.71 + 0.14x,r = 0.999, n = 3) and in the range 0.9–8.9 ppm (regression equation; Y = 1.34 + 0.17x,r = 0.980, n = 3), respectively. A particular advantage of using the mercury‐modified SPE rather than the nickel‐modified base card is that the well‐defined electrochemistry of furan derivatives allow them to be individually distinguished. The half‐wave potentials at the mercury SPE for 2‐furaldehyde (E1/2 = −1.15 V vs. Ag/AgCl) and two possible interferents 2‐acetyl‐furan and 5‐methyl‐2‐furaldehyde (E1/2 = −1.2 and −1.31 V vs. Ag/AgCl) are sufficiently well separated to allow the individual components to be resolved whereas at a nickel‐modified SPE a combined signal is observed.
Electrochemistry of hemoglobin at modified silver electrodes is not a redox‐process of iron protoporphyrin IX
Authors: Katterle Martin , Wollenberger Ulla , Scheller Frieder W. 
Published: May 2005

AbstractThe direct heterogenous electron transfer between hemoglobin and modified silver and gold electrodes has been investigated using cyclic voltammetry. Cathodic and anodic peak currents have been obtained for hemoglobin, methemoglobin, carbonylhemoglobin, cyanohemoglobin and oxyhemoglobin, as well as for apohemoglobin and bovine serum albumin, exclusively at modified silver electrodes at potentials around 70 and 270 mV (vs. Ag/AgCl). The results demonstrate that the observed redox chemistry was not a result of direct electron transfer to the redox centre protoporphyrin IX. Spectrometrical measurements were made to substantiate this conclusion. A possible reaction mechanism which takes place at the modified silver electrode is suggested.
Digital simulation of potential step experiments using the extrapolation method
Authors: Strutwolf JÖRg , Schoeller Wolfgang W. 
Published: May 2005

AbstractFor large values of the model diffusion coefficient the Crank‐Nicolson scheme produces poor numerical results, if it is used for the simulation of a potential step experiment. On the other hand the Backward Euler or fully implicit scheme, not suffering from this drawback, is of lower accuracy. We apply the extrapolation method introduced by Morris et al. to the simulation of Cottrellian diffusion and to a simple catalytic mechanism. The extrapolation method, does not show the oscillating behavior of numerical solutions and is of higher accuracy than the fully implicit scheme. Comparison to other implicit difference schemes are presented. The extrapolation schemes show superior results for the diffusional problem and for the short time behavior of the catalytic mechanism.
The problem of complex curves in normal pulse polarography
Authors: Sanecki Przemysław , Lechowicz Jaromir 
Published: May 2005

AbstractTwo types of complex curves are discussed: (I) those obtained for binary mixtures of substances redcing at similar potentials and (II) those corresponding to the two‐electron consecutive processes: O → Z → R and O ⇌ Z → R. A convenient procedure of curve fitting for the above two cases of complex normal pulse polarographic (NPP) curves is presented and applied for some two‐electron consecutive electroreductions.
Temporal profiles of neuronal degeneration, glial proliferation, and cell death in hNFL(+/+) and NFL(−/−)mice
Authors: McLean Jesse R. , Sanelli Teresa R. , Leystra‐Lantz Cheryl , He Bei Ping , Strong Michael J. 
Published: May 2005

AbstractNeurofilament (NF) aggregate formation within motor neurons is a pathological hallmark of both the sporadic and familial forms of amyotrophic lateral sclerosis (ALS). The relationship between aggregate formation and both microglial and astrocytic proliferation, as well as additional neuropathological features of ALS, is unknown. To examine this, we have used transgenic mice that develop NF aggregates, through either a lack of the low‐molecular‐weight NF subunit [NFL (−/−)] or the overexpression of human NFL [hNFL (+/+)]. Transgenic and wild‐type C57bl/6 mice were examined from 1 month to 18 months of age, and the temporal pattern of motor neuron degeneration, microglial and astrocytic proliferation, and heat shock protein‐70 (HSP‐70) expression characterized. We observed three overlapping phases in both transgenic mice, including transient aggregate formation, reactive microgliosis, and progressive motor neuron loss. However, only NFL (−/−) mice demonstrated significant astrogliosis and HSP‐70 upregulation in both motor neurons and astrocytes. These in vivo models suggest that the development of NF aggregates in motor neurons leads to motor neuron death, but that the interaction between the degenerating motor neurons and the adjacent non‐neuronal cells may differ significantly depending on the etiology of the NF aggregate itself. © 2005 Wiley‐Liss, Inc.
CD46 on glial cells can function as a receptor for viral glycoprotein‐mediated cell–cell fusion
Authors: Cassiani‐Ingoni Riccardo , Greenstone Heather L. , Donati Donatella , Fogdell‐Hahn Anna , Martinelli Elena , Refai Daniel , Martin Roland , Berger Edward A. , Jacobson Steven 
Published: May 2005

AbstractMembrane cofactor protein (CD46) is a regulator of complement activation that also serves as the entry receptor for human herpes virus 6 (HHV‐6) and measles virus (MV) into human cells. While it is clear that oligodendrocytes and astrocytes are cell types commonly infected by these viruses, it is unclear whether oligodendrocytes express CD46, or which are the cellular mechanisms underlying the infection. We show that adult oligodendrocytes, as well as astrocytes and microglial cells, express CD46 on the cellular surface. Moreover, we employed a quantitative fusion assay to demonstrate that HHV‐6A infection of T lymphocytes enables cell–cell fusion of these cells to astrocytes or to oligodendroglial cells. This fusion is mediated by the interaction between viral glycoproteins expressed on the membrane of the infected cells and CD46 on the glial targets, and is also observed using cells expressing recombinant MV glycoproteins. These data suggest a mechanism that involves cell–cell fusion by which certain viruses could spread the infection from the periphery to the cells in the nervous system. Published 2005 Wiley‐Liss, Inc.
Effects of cytokines on microglial phenotypes and astroglial coupling in an inflammatory coculture model
Authors: Hinkerohe Daniel , Smikalla Dirk , Haghikia Aiden , Heupel Katharina , Haase Claus G. , Dermietzel Rolf , Faustmann Pedro M. 
Published: May 2005

AbstractCytokines play an important role in the onset, regulation, and propagation of immune and inflammatory responses within the central nervous system (CNS). The main source of cytokines in the CNS are microglial cells. Under inflammatory conditions, microglial cells are capable of producing pro‐ and antiinflammatory cytokines, which convey essential impact on the glial and neuronal environment. One paramount functional feature of astrocytes is their ability to form a functionally coupled syncytium. The structural link, which is responsible for the syncytial behavior of astrocytes, is provided by gap junctions. The present study was performed to evaluate the influence of inflammation related cytokines on an astroglial/microglial inflammatory model. Primary astrocytic cultures of newborn rats were cocultured with either 5% (M5) or 30% (M30) microglial cells and were incubated with the following proinflammatory cytokines: tumor necrosis factor‐α (TNF‐α), interleukin‐1β (IL‐1β), interleukin‐6 (IL‐6), interferon‐γ (IFN‐γ), and the antiinflammatory cytokines transforming growth factor‐β1 (TGF‐β1) and IFN‐β. Under these conditions, i.e., incubation with the inflammatory cytokines and the high fraction of microglia (M30), microglial cells revealed a significant increase of activated round phagocytotic cells accompanied by a reduction of astroglial connexin 43 (Cx43) expression, a reduced functional coupling together with depolarization of the membrane resting potential (MRP). When the antiinflammatory mediator TGF‐β1 was added to proinflammatory altered M30 cocultures, a reversion of microglial activation and reconstitution of functional coupling together with recovery of the astroglial MRP was achieved. Finally IFN‐β, added to M5 cocultures was able to prevent the effects of the proinflammatory cytokines TNF‐α, IL‐1β, and IFN‐γ. © 2005 Wiley‐Liss, Inc.