Stability and Sensitivity Enhanced Electrochemical In Vivo Superoxide Microbiosensor Based on Covalently Co-immobilized Lipid and Cytochrome c

Enhanced stability and sensitivity of a superoxide anion radical (O(2)(?-)) microbiosensor were achieved through the sequential immobilization of lipid and cytochrome c (Cyt c) covalently bonded onto a conducting polymer layer that showed a clear quasi-reversible direct electron transfer (DET) process. The formal potential and the apparent standard rate constant were determined to be -0.24 V and 0.62 ± 0.05 s(-1), respectively. The detection of O(2)(?-) was attained through the catalytic activity of the haem group of Cyt c stabilized by coimmobilized lipid molecules (1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine-n-dodecanylamine (DGPD)). The linear dynamic range and the detection limit of the O(2)(?-) analysis were determined to be 0.2-6.0 nM and 30.0 ± 0.9 pM, respectively. The in vivo microbiosensor implanted into rat brain successfully determined the extracellular level of O(2)(?-) produced by acute and repeated injections of cocaine. The present O(2)(?-) microbiosensor could be an effective tool for monitoring the change in extracellular O(2)(?-) levels in response to stimulant drug exposure.     

Electrospray ionization tandem mass spectrometry analysis of the reactivity of structurally related bromo-methyl-benzoquinones toward oligonucleotides

We report the use of electrospray ionization tandem mass spectrometry (ESI-MS/MS) as a tool for rapid screening of structurally related chemicals toward oligonucleotides using the binding of five bromobenzoquinones with single-stranded (ss) and double-stranded (ds) oligonucleotides (ODNs) as a model. We found that these compounds interact differentially with oligonucleotides depending on the extent of their bromination and methylation. Three dibromobenzoquinones, 2,6-dibromo-1,4-benzoquinone (2,6-DBBQ), 2,5-dibromo-1,4-benzoquinone (2,5-DBBQ), and 2,5-dimethyl-3,6-dibromo-1,4-benzoquinone (DMDBBQ), bound to ssODN to form 1:1 adducts, and the binding constant of DMDBBQ bound to ssODN was 100-fold lower than those of 2,6-DBBQ and 2,5-DBBQ to ssODN, indicating that methyl groups hindered interactions of the bromoquinones with ODNs. Collision-induced dissociation (CID) of the 1:1 and 1:2 adducts of ODN with 2,6-DBBQ and 2,5-DBBQ demonstrated neutral loss of DBBQ and charge separations. Incubation of two tetrabromobenzoquinones (TBBQ), 2,3,5,6-tetrabromo-1,4-benzoquinone and 3,4,5,6-tetrabromo-1,2-benzoquinone, with the same ODNs did not form any adducts of TBBQ with ssODN or dsODN; however, bromide-ODNs were detected. Fragmentation of the bromide-ODN adducts showed loss of the HBr molecule, supporting the presence of bromide on ODNs. High-resolution MS and MS/MS analysis of the mixtures of dinucleotides (AA, GG, CC, and TT) and TBBQ confirmed the presence of bromide on the dinucleotides, supporting the transfer of bromide to ODNs through interaction with TBBQ. This study presents evidence of differential interactions of structurally related bromo and methyl-benzoquinones with oligonucleotides and demonstrates a potential application of ESI-MS/MS analysis of chemical interactions with ODN for rapid screening of the reactivity of other structurally related environmental contaminants toward DNA.     

Ratiometric coumarin-neutral red (CONER) nanoprobe for detection of hydroxyl radicals

Excessive production of reactive oxygen species can lead to alteration of cellular functions responsible for many diseases including cardiovascular diseases, neurodegenerative diseases, cancer, and aging. Hydroxyl radical is a short-lived radical which is considered very aggressive due to its high reactivity toward biological molecules. In this study, a COumarin-NEutral Red (CONER) nanoprobe was developed for detection of hydroxyl radical based on the ratiometric fluorescence signal between 7-hydroxy coumarin 3-carboxylic acid and neutral red dyes. Biocompatible poly lactide-co-glycolide (PLGA) nanoparticles containing encapsulated neutral red were produced using a coumarin 3-carboxylic acid conjugated poly(sodium N-undecylenyl-Nε-lysinate) (C3C-poly-Nε-SUK) as moiety reactive to hydroxyl radicals. The response of the CONER nanoprobe was dependent on various parameters such as reaction time and nanoparticle concentration. The probe was selective for hydroxyl radicals as compared with other reactive oxygen species including O(2)(?-), H(2)O(2), (1)O(2), and OCl(-). Furthermore, the CONER nanoprobe was used to detect hydroxyl radicals in vitro using viable breast cancer cells exposed to oxidative stress. The results suggest that this nanoprobe represents a promising approach for detection of hydroxyl radicals in biological systems.     

Development of a silver nanoparticle-based method for the antioxidant capacity measurement of polyphenols

A sensitive colorimetric method for the detection of polyphenols (i.e., flavonoids, simple phenolic, and hydroxycinnamic acids) was proposed in this research based on the reduction of Ag(+) ions by polyphenols in the presence of citrate-stabilized silver seeds. The color of the stable suspension was controlled by varying the concentration of trisodium citrate, silver nitrate, and silver seeds. The reduction of Ag(+) to spherical silver nanoparticles (SNPs) by polyphenols in the presence of trisodium citrate and silver seeds produced a very intense surface plasmon resonance (SPR) absorption band of SNPs at 423 nm. The plasmon absorbance of SNPs allows the quantitative spectrophotometric detection of the polyphenols, and the developed method gave a linear response over a wide concentration range of standard polyphenolic compounds. In contrast to other reported NP-based antioxidant assays, it was established in this work that growth but not nucleation of SNPs gave a linear concentration-dependent response. The trolox equivalent antioxidant capacity (TEAC) values of various (hydrophilic and lipophilic) antioxidants using the developed method were comparable to those of the CUPRAC assay. Common food ingredients like oxalate, citrate, fruit acids, amino acids, and reducing sugars did not interfere with the proposed sensing method. This assay was validated through linearity, additivity, precision and recovery, demonstrating that the assay is reliable and robust. The developed method was used to screen total antioxidant capacity (TAC) of some commercial fruit juices and herbal teas without preliminary treatment, and showed a promising potential for the preparation of antioxidant inventories of a wide range of food plants.     

适宜于花生酱抗氧化应用的天然抗氧化剂筛选

目的筛选适宜于花生酱抗氧化应用的天然抗氧化剂,抑制花生酱油脂氧化。方法以花生酱为原料,以不添加抗氧化剂为对照组,以添加化学合成抗氧化剂TBHQ和异Vc为参照,分别添加天然抗氧化剂迷迭香提取物、VE、茶多酚、植酸、β-胡萝卜素及Vc,定期测定花生酱的酸价和过氧化值,判别不同抗氧化剂的抗氧化效果。结果不同的天然抗氧化剂对花生酱的抗氧化效果存在明显差异,迷迭香提取物和茶多酚在花生酱中表现出较好的抗氧化效果,迷迭香提取物的抗氧化效果优于茶多酚,而Vc、VE、β-胡萝卜素和植酸在花生酱中表现为促进氧化。添加迷迭香提取物、茶多酚、异Vc和TBHQ抗氧化剂的花生酱在储存150 d时,酸价与对照组相比低了66.62%,46.14%,65.45%,83.77%,过氧化值与对照组相比低了56.73%,24.28%,38.32%,94.06%。迷迭香提取物在抑制酸价升高方面与异Vc相当,在抑制过氧化值升高方面优于异Vc,其整体抗氧化效果略逊色于TBHQ。结论在天然抗氧化剂添加量(质量分数)均为0.03%时,迷迭香提取物和茶多酚对花生酱抗氧化效果优于其他天然抗氧化剂,可应用于花生酱的抗氧化领域。     

Lithium/sulfur cell discharge mechanism: an original approach for intermediate species identification

The lithium/sulfur battery is a promising electrochemical system that has a high theoretical capacity of 1675 mAh g(-1), but its discharge mechanism is well-known to be a complex multistep process. As the active material dissolves during cycling, this discharge mechanism was investigated through the electrolyte characterization. Using high-performance liquid chromatography, UV-visible absorption, and electron spin resonance spectroscopies, we investigated the electrolyte composition at different discharge potentials in a TEGDME-based electrolyte. In this study, we propose a possible mechanism for sulfur reduction consisting of three steps. Long polysulfide chains are produced during the first reduction step (2.4-2.2 V vs Li(+)/Li), such as S(8)(2-) and S(6)(2-), as evidenced by UV and HPLC data. The S(3)(?-) radical can also be found in solution because of a disproportionation reaction. S(4)(2-) is produced during the second reduction step (2.15-2.1 V vs Li(+)/Li), thus pointing out the gradual decrease of the polysulfide chain lengths. Finally, short polysulfide species, such as S(3)(2-), S(2)(2-), and S(2-), are produced at the end of the reduction process, i.e., between 2.1 and 1.9 V vs Li(+)/Li. The precipitation of the poorly soluble and insulating short polysulfide compounds was evidenced, thus leading to the positive electrode passivation and explaining the early end of discharge.     

Humic acid induced genotoxicity in human peripheral blood lymphocytes using comet and sister chromatid exchange assay

Humic acid (HA) in well water used by the inhabitants for drinking is one of the possible etiological factors for blackfoot disease (BFD). Moreover, within BFD endemic areas cancers occur at significantly higher rates than in areas free of BFD. In this study, the genotoxic potential of HA is assessed using human peripheral blood lymphocytes. The cells were exposed to HA (0-200 microg/mL for 2 h), and the induction of DNA primary damage in cellular DNA was evaluated by single-cell gel electrophoresis (comet assay). HA-induced DNA damage was decreased by superoxide (O(2)(-)), hydrogen peroxide (H(2)O(2)), and reactive oxygen species (ROS) scavengers (superoxide dismutase, catalase, and Trolox), and nitric oxide (NO) synthase inhibitors (N(G)-nitro-l-arginine methyl ester and N(G)-methyl-l-arginine). Moreover, formamidopyrimidine-DNA glycosylase (Fpg) and endonuclease III (Endo III), known to catalyze the excision of oxidized bases, increase the amount of DNA migration in HA-treated cells. Pretreatment of the cells with both the Ca(2+)-chelator BAPTA and EGTA completely inhibited HA-induced DNA damage, indicating that HA-induced changes in Ca(2+)-homeostasis are the predominant pathways for the HA induction of genotoxicity. Furthermore, sister chromatid exchange was found in the HA-treated lymphocytes. Our findings suggest that HA can induce oxidative DNA damage and genotoxicity in human lymphocytes.     

Direct voltammetry and catalysis with Mycobacterium tuberculosis catalase-peroxidase, peroxidases, and catalase in lipid films.

Stable films of dimyristoylphosphatidylcholine and M. tuberculosis catalase-peroxidase (KatG), several peroxidases, myoglobin, and catalase showed reversible FeIII/FeII voltammetry on pyrolytic graphite electrodes and catalytic current for hydrogen peroxide and oxygen. Amperometric responses for these films to H2O2 at 0 V are likely to contain significant contributions from catalytic reduction of oxygen produced during the catalytic cycles. Relative apparent turnover rates at pH 6 based on steady-state currents at 0 V versus SCE in the presence of H2O2 were in the order horseradish peroxidase > cytochrome c peroxidase (CcP) > soybean peroxidase > myoglobin > KatG > catalase. Lower currents for the very efficient peroxide scavengers KatG and catalase may be related to the instability of their compounds I in the presence of H2O2. KatG catalyzed the electrochemical reduction of oxygen more efficiently than catalase and CcP but less efficiently than the other peroxidases. DMPC films incorporating glucose oxidase and peroxidases gave good analytical responses to glucose, demonstrating the feasibility of dual enzyme-lipid films for biosensor fabrication.     

Automated electrochemical free radical scavenger screening in dietary samples

An automated electrochemical microtiter plate assay for the quantification of free radical scavengers (antioxidants) in food samples is described. Dietary antioxidant capacity measurements were achieved using the radical compound 2,2-diphenyl-1-picrylhydrazyl (DPPH·) as an amperometric redox indicator, with a pencil lead working electrode, in conjunction with a Pt counter-electrode and Ag/AgCl reference electrode, moving sequentially through the 24 vials of a standard 6 × 4 microtiter plate. Programmed analyses were performed successfully with synthetic antioxidants of known concentrations and with tea infusions, fruit juices, and vegetable extracts. The novel methodology is simple and convenient as, unlike common DPPH· antioxidant electroanalysis, it avoids the time-consuming cleaning of electrochemical cells between measurements. Microtiter plate-based robotic electrochemical antioxidant assaying is thus a good option for handling large sample collections and may be applicable in the production of food and herbal remedies.     

Determination of benzo[a]pyrene-7,10-quinone in airborne particulates by using a chemiluminescence reaction of hydrogen peroxide and hydrosulfite

An ultraweak chemiluminescence (CL) was observed when sodium hydrosulfite (NaHSO(3)) reacts with hydrogen peroxide (H(2)O(2)) and was enhanced 70 times by adding 10 pmol benzo[a]pyrene-7,10-quinone (7,10-BaPQ). The CL reaction is fast, and it reached maximum intensity in 0.1 s, and then decayed to baseline in 3 s. Mechanism of NaHSO(3)-7,10-BaPQ-H(2)O(2) system were investigated by CL spectrum, radical scavengers and electron spin resonance (ESR). Hydroxyl radical ((?)OH), super oxide anion radical ((?)O(2)(-)), and sulfite radical ((?)SO(3)(-)) were generated in the NaHSO(3)-7, 10-BaPQ-H(2)O(2) system. Reduction of 7,10-BaPQ by (?)O(2)(-) radical gave excited semiquinone, which showed strong CL emission when decayed to its ground state. Maximum CL emission wavelength was located at 440 nm, which may belong to the excited semiquinone. This CL system was developed as post column detection of high performance liquid chromatography for the determination of 7,10-BaPQ. Linearity ranged from 50 fmol to 20 pmol (R(2) = 0.9995) with limit of detection of 30 fmol (S/N = 3). The proposed method was used to determine 7,10-BaPQ in airborne particulates. Average atmospheric concentrations of 7,10-BaPQ in Kanazawa in December 2010 and Wajima in October 2007 were 2.0 and 1.6 pg/m(3), respectively.     

(Na0.5Bi0.5)TiO3基弛豫铁电体相变的研究进展

钛酸铋钠((Na0.5Bi0.5)TiO3,NBT)是一种典型的A位复合钙钛矿结构弛豫铁电体,具有复杂的相变序列,介电温度峰呈现明显的弛豫性.总结了NBT弛豫铁电体的相变及NBT基复合铁电体准同型相界的研究进展;从晶体结构出发,通过与B位复合型钙钛矿结构弛豫铁电体类比,对A位复合型NBT的弛豫机理进行了探讨,提出NBT弛豫性来源于其A位离子有序-无序引起的B位离子位移的变化.     

Direct determination of oxygen by HPLC. 1. Basic principles of a sensitive and selective oxygen sensor

The basic principles of a novel, versatile, sensitive, and selective oxygen-sensing assay are presented in this paper. For the first time, liquid chromatography with electrochemical detection (at the hmde) has been used for the determination of oxygen. All factors concerning optimization of the chromatographic separation conditions and electrochemical detection with respect to direct determination of oxygen even in complex biological samples are discussed. Due to the combination of a chromatographic technique with amperometric detection, a high selectivity can be achieved. A direct and linear relationship between the oxygen concentration in the sample and the reduction current was verified in a large concentration range from saturation down to trace level oxygen concentrations. The novel oxygen-sensing assay provides a much higher sensitivity compared to conventional oxygen sensors. In principle, O(2) concentrations down to 4.5 × 10(-)(9) mol L(-)(1) O(2) (corresponding to a signal-to-noise ratio of 3) can be detected. Precision was determined by repeated measurements (n = 6) of air-saturated solutions (2.5 × 10(-)(4) mol L(-)(1) O(2), 20 °C, 920 mbar) which yielded relative standard deviations of lower than 0.2%.     

Structural and electrical properties of donor-doped NBT system synthesized by microwave-assisted solid-state reaction route

Journal of Materials Science: Materials in Electronics - A-site donor-doped NBT systems (Na0.5Bi0.5)1-xMxTi(1-x/4)O3 (M?=?La and Sm) were synthesized by microwave-assisted solid-state...     

Degradation process of lead chromate in paintings by Vincent van Gogh studied by means of synchrotron X-ray spectromicroscopy and related methods. 1. Artificially aged model samples

On several paintings by artists of the end of the 19th century and the beginning of the 20th Century a darkening of the original yellow areas, painted with the chrome yellow pigment (PbCrO(4), PbCrO(4)·xPbSO(4), or PbCrO(4)·xPbO) is observed. The most famous of these are the various Sunflowers paintings Vincent van Gogh made during his career. In the first part of this work, we attempt to elucidate the degradation process of chrome yellow by studying artificially aged model samples. In view of the very thin (1-3 μm) alteration layers that are formed, high lateral resolution spectroscopic methods such as microscopic X-ray absorption near edge (μ-XANES), X-ray fluorescence spectrometry (μ-XRF), and electron energy loss spectrometry (EELS) were employed. Some of these use synchrotron radiation (SR). Additionally, microscopic SR X-ray diffraction (SR μ-XRD), μ-Raman, and mid-FTIR spectroscopy were employed to completely characterize the samples. The formation of Cr(III) compounds at the surface of the chrome yellow paint layers is particularly observed in one aged model sample taken from a historic paint tube (ca. 1914). About two-thirds of the chromium that is present at the surface has reduced from the hexavalent to the trivalent state. The EELS and μ-XANES spectra are consistent with the presence of Cr(2)O(3)·2H(2)O (viridian). Moreover, as demonstrated by μ-XANES, the presence of another Cr(III) compound, such as either Cr(2)(SO(4))(3)·H(2)O or (CH(3)CO(2))(7)Cr(3)(OH)(2) [chromium(III) acetate hydroxide], is likely.     

Influence of inorganic anion on Cr(VI) photo-reduction in the presence of ferric ion

Photo-reduction of Cr(VI) in a solution with single or multi-inorganic anions was evaluated. The results show that 38.5 microM Cr(VI) is photo-reduced in the presence of NO(3)(-) at pH 1. The photolysis of NO(3)(-), producing NO(2)(-) or H(2)O(2), may contribute to Cr(VI) reduction. The addition of 0.001-0.1 M chlorite to NO(3)(-) enhanced Cr(VI) photo-reduction when 35.8 microM Fe(III) was present. This enhancement was the combinative result of photolysis of NO(3)(-) and Fe-Cl complexes, leading to the formation of NO(2)(-) and Fe(II), respectively, for Cr(VI) reduction. On the contrary, a significant decrease in Cr(VI) photo-reduction was observed with the addition of PO(4)(3-) and SO(4)(2-). This decrease was due to their strong competition with Fe(III) from Cl(-), resulting in a marked decrease in the concentrations of Fe-Cl complexes. The results suggest that a direct irradiation of acidic wastewaters containing Cl(-), NO(3)(-), and Fe(III) is a feasible strategy for eliminating Cr(VI).     

Preparation, characterization, and application of an enzyme-immobilized magnetic microreactor for flow injection analysis

Enzyme-immobilized magnetic microparticles (EMMP) have been prepared for use as a microreactor in flow injection analysis (FI). The microparticles were directly injected into the FI system. Their retention occurred within the flow line by small permanent magnets located near the detector. The analytical utility of this concept was illustrated by the assay of glucose using glucose oxidase (GOx), immobilized microparticles, and amperometric detection of liberated hydrogen peroxide. The microparticles were derived from silica gel (nominal pore diameter, 15-80 nm) by impregnation with a citric acid/ethanol solution and a ferric nitrate/ethanol solution and then by calcination in a nitrogen atmosphere to produce ferrimagnetic fine particles of spinel-type iron oxide (gamma-Fe(2)O(3)) inside the pore. They were characterized by X-ray diffraction. The calibration curve of the glucose sample (2 microL injected) was linear between 2.5 x 10(-6) and 5 x 10(-4) mol/L (R = 0.9995), and the detection limit was 1.0 x 10(-6) mol/L or 0.36 ng of injected glucose (S/N = 3). The repeatability for a 5 x 10(-4) mol/L glucose solution was RSD = 1.5% (n = 6). Application to the assay of glucose in a fermentation broth is illustrated. The GOx MMP were stable and active for more than eight months when kept at 10 degrees C.     

On-line detection of antioxidative activity in high-performance liquid chromatography eluates by chemiluminescence

Luminol chemiluminescence (CL) was employed for the on-line detection of radical scavengers in HPLC eluates. Optimization of CL reagents and instrumental setup resulted in a steady postcolumn luminol photochemical reaction in the presence of microperoxidase and hydrogen peroxide at pH 10. Quenching of the CL signal was utilized to detect radical scavenging activity of both natural and synthetic antioxidants at the nanogram level. The detection system can be used with isocratic or gradient elution. Several antioxidative compounds were detected in thyme and sage acetone extracts. Quantitative results can be obtained when antioxidants are analyzed at certain concentrations. The method is suitable for rapid screening of antioxidants in crude extracts.     

Application of ABTS radical cation for selective on-line detection of radical scavengers in HPLC eluates

The radical cation 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonate), (ABTS*+) was utilized in an on-line HPLC method for the detection of radical scavengers in complex matrixes. The HPLC-separated analytes react postcolumn with the preformed ABTS*+, and the induced bleaching is detected as a negative peak by an absorbance detector at 734 nm. An optimized instrumental and experimental setup is presented. The method is suitable for both isocratic and gradient HPLC runs using mobile phases containing 100% organic solvent or its solution in water, weak acids, or buffers (pH 3-7.4). The method is sensitive, selective, relatively simple, applicable to compounds of different chemical natures; uses common instruments and inexpensive reagents; and has a time-saving, nonlaborious experimental protocol. It can also be used for quantitative analysis. The method was applied to several pure natural antioxidants and plant extracts. The minimum detectable concentration varied from 0.02 to 0.13 microg/mL, depending on the compound tested. The method can be applied to perform kinetic studies, which is illustrated by determination of Trolox equivalent antioxidant capacities (TEAC) of several known antioxidants in flow injection mode.     

Least cost SO2 emission minimization for a petroleum refinery by optimum use of source reduction, tail gas treatment and flue gas desulphurization

With the growing awareness on the necessity to preserve the environment, pollution standards are turning more stringent and minimization of waste at the source has become the first choice option rather than the end-of-pipe treatment. The objective of the present research is to identify the optimum combination of source reduction (SR), tail gas treatment (TGT) and flue gas desulphurization (FGD) to minimize the total cost of overall SO₂ emission from a petroleum refinery to various desired limits. It has been found that for the typical refinery considered, the TGT is the lowest cost option than either SR or FGD; however, only a maximum of ~12.5% reduction is achievable through the TGT. After full utilization of TGT, for the next range of SO₂ emission reductions from ~12.5% to ~64%, the SR is more economical than FGD. For a still stringent SO₂ emission limit, i.e. SO₂ emission reduction higher than ~64%, the full utilization of the TGT and the optimum use of SR and FGD are the best options.     

Degradation process of lead chromate in paintings by Vincent van Gogh studied by means of synchrotron X-ray spectromicroscopy and related methods. 2. Original paint layer samples

The darkening of the original yellow areas painted with the chrome yellow pigment (PbCrO(4), PbCrO(4)·xPbSO(4), or PbCrO(4)·xPbO) is a phenomenon widely observed on several paintings by Vincent van Gogh, such as the famous different versions of Sunflowers. During our previous investigations on artificially aged model samples of lead chromate, we established for the first time that darkening of chrome yellow is caused by reduction of PbCrO(4) to Cr(2)O(3)·2H(2)O (viridian green), likely accompanied by the presence of another Cr(III) compound, such as either Cr(2)(SO(4))(3)·H(2)O or (CH(3)CO(2))(7)Cr(3)(OH)(2) [chromium(III) acetate hydroxide]. In the second part of this work, in order to demonstrate that this reduction phenomenon effectively takes place in real paintings, we study original paint samples from two paintings of V. van Gogh. As with the model samples, in view of the thin superficial alteration layers that are present, high lateral resolution spectroscopic methods that make use of synchrotron radiation (SR), such as microscopic X-ray absorption near edge (μ-XANES) and X-ray fluorescence spectrometry (μ-XRF) were employed. Additionally, μ-Raman and mid-FTIR analyses were carried out to completely characterize the samples. On both paint microsamples, the local presence of reduced Cr was demonstrated by means of μ-XANES point measurements. The presence of Cr(III) was revealed in specific areas, in some cases correlated to the presence of Ba(sulfate) and/or to that of aluminum silicate compounds.