RAPID-DETERMINATION OF KINETIC-PARAMETERS FOR THE ELECTROCATALYTIC REDUCTION OF DIOXYGEN BY VITAMIN-B12 ADSORBED ON GLASSY-CARBON ELECTRODE

In this paper, the electrochemical behavior of vitamin B-12, ie cyanocobalamin (abbr. VB12) in a weak acidic aqueous solution and adsorbed on glassy carbon (GC) surface (abbr. VB12(ad)/GC) in different pH buffer solutions have been described by using cyclic voltammetry (cv). It is found that VB12 and VB12(ad)/GC exhibit catalytic activity for the electroreduction of O2 according to two reduction peaks at -0.50 and -1.00 V vs. sce; but their electrocatalytic activity is very unstable. Based on the method of hydrodynamic amperometry [B. Miller and S. Bruckenstein, J. electrochem. Soc. 117, 1033 (1970)], some kinetic parameters for the electrocatalytic reduction of O2 by VB12(ad)/GC have been determined rapidly by using a linear rotation-scan method [Rongzhong Jiang and Shaojun Dong, Electrochim. Acta 35, 1451 (1990)]. These kinetic parameters indicate that the reduction of O2 on VB12(ad)/GC gives water predominantly in both potential ranges which correspond to those two reduction peaks. Possible reaction mechanisms have been suggested.

ELECTROCATALYSIS AND DETERMINATION OF HYDRAZINE COMPOUNDS IN LIQUID-CHROMATOGRAPHY AT A MIXED-VALENT COBALT OXIDE CYANOCOBALTATE FILM ELECTRODE

A glassy carbon electrode coated with an electrodeposited film of mixed-valent cobalt oxide/cyanocobaltate (Co-O/CN-Co) enabled hydrazine compounds to be catalytically oxidized at the greatly reduced overpotential and in a wide operational pH range (pH 2.0-7.0). Electrocatalytic activity at the Co-O/CN-Co modified electrode was evaluated with respect to solution pH, film thickness, supporting electrolyte ions, potential scan rate, operating potential, concentration dependence and other variables. The Co-O/CN-Co film electrode was completely compatible with a conventional reversed-phase liquid chromatographic (RP-LC) system. Practical RP-LC amperometric detection (RP-LCEC) of hydrazines was performed. A dynamic linear response range over three orders of magnitude and a detection limit at the pmol level were readily obtained. The Co-O/CN-CO film electrode exhibited excellent electrocatalytic stability in the flowing streams.

ON THE SIGNIFICANCE OF WAVELENGTH POSITIONING ACCURACY IN MULTICOMPONENT ANALYSIS TECHNIQUES FOR THE CORRECTION OF LINE INTERFERENCES IN INDUCTIVELY COUPLED PLASMA ATOMIC EMISSION-SPECTROMETRY

The present paper reports some definite evidence for the significance of wavelength positioning accuracy in multicomponent analysis techniques for the correction of line interferences in inductively coupled plasma atomic emission spectrometry (ICP-AES). Using scanning spectrometers commercially available today, a large relative error, DELTA(A) may occur in the estimated analyte concentration, owing to wavelength positioning errors, unless a procedure for data processing can eliminate the problem of optical instability. The emphasis is on the effect of the positioning error (deltalambda) in a model scan, which is evaluated theoretically and determined experimentally. A quantitative relation between DELTA(A) and deltalambda, the peak distance, and the effective widths of the analysis and interfering lines is established under the assumption of Gaussian line profiles. The agreement between calculated and experimental DELTA(A) is also illustrated. The DELTA(A) originating from deltalambda is independent of the net analyte/interferent signal ratio; this contrasts with the situation for the positioning error (dlambda) in a sample scan, where DELTA(A) decreases with an increase in the ratio. Compared with dlambda, the effect of deltalambda is generally less significant.

WAVELENGTH POSITIONING ERRORS AND TRUE DETECTION LIMIT IN RELATION TO MULTICOMPONENT ANALYSIS TECHNIQUES FOR THE CORRECTION OF LINE INTERFERENCES IN INDUCTIVELY COUPLED PLASMA ATOMIC EMISSION-SPECTROMETRY

The present paper deals with the evaluation of the relative error (DELTA(A)) in estimated analyte concentrations originating from the wavelength positioning error in a sample scan when multicomponent analysis (MCA) techniques are used for correcting line interferences in inductively coupled plasma atomic emission spectrometry. In the theoretical part, a quantitative relation of DELTA(A) with the extent of line overlap, bandwidth and the magnitude of the positioning error is developed under the assumption of Gaussian line profiles. The measurements of eleven samples covering various typical line interferences showed that the calculated DELTA(A) generally agrees well with the experimental one. An expression of the true detection limit associated with MCA techniques was thus formulated. With MCA techniques, the determination of the analyte and interferent concentrations depend on each other while with conventional correction techniques, such as the three-point method, the estimate of interfering signals is independent of the analyte signals. Therefore. a given positioning error results in a larger DELTA(A) and hence a higher true detection limit in the case of MCA techniques than that in the case of conventional correction methods. although the latter could be a reasonable approximation of the former when the peak distance expressed in the effective width of the interfering line is larger than 0.4. In the light of the effect of wavelength positioning errors, MCA techniques have no advantages over conventional correction methods unless the former can bring an essential reduction ot the positioning error.

MEASUREMENT OF CATALYTIC ACTIVITY VARIATION FOR H2O2 OXIDATION AT A COBALT PORPHYRIN COATED ELECTRODE

A rapid rotation-scan method was used for the electrocatalytic oxidation of H2O2 at a cobalt protoporphyrin modified pyrolytic graphite electrode (CoPP/PG). The rate constant of H2O2 oxidation at the CoPP/PG electrode at different potentials and in different pH solutions was measured. The variation of catalytic activity with reaction charges (Q) passed through the electrode was analyzed. This provided a convenient electrochemical method to study the passivation and poisoning of catalytic sites with time.

A STUDY ABOUT PH CHEMICALLY MODIFIED ELECTRODES BASED ON AMINO-DERIVATIVES OF NAPHTHALENE

The electrochemical polymerization of amino-derivatives of naphthalene has been studied on the platinum wire electrodes. The effects of acidity of the modifying media and the potential scan rate on the cyclic voltammograms are verified. As potentiometric pH sensors, the electrodes prepared from 1-naphthylamine and 2,3-diaminonaphthalene showed performance characteristics superior to some other electrodes tested. The electrode modified with 1-naphthylamine in the optimum medium showed a nearly Nernstian response of 4.20-13.70 pH and a slope of -54.8 mV/pH, while the linear range of the electrode prepared by 2,3-diaminonaphthalene was 4.00-13.60 pH, with a slope of -52.4 mV/pH.

AMPEROMETRIC FLOW-INJECTION ANALYSIS OF HYDRAZINE BY ELECTROCATALYTIC OXIDATION AT COBALT TETRAPHENYLPORPHYRIN MODIFIED ELECTRODE WITH HEAT-TREATMENT

Chemically modified electrodes prepared by treating the cobalt tetraphenylporphyrin modified glassy-carbon electrode at 750-degrees (HCME) are shown to catalyze the electrooxidation of hydrazine. The oxidation occurred at +0.63 V vs. Ag/AgCl (saturated potassium chloride) in pH 2.5 media. The catalytic response is evaluated with respect to solution pH, potential scan-rate, concentration dependence and flow-rate. The catalytic stability of the HCME is compared with that of the cobalt tetraphenylporphyrin adsorbed glassy-carbon electrode. The stability of the HCME was excellent in acidic solution and even in solutions containing organic solvent (50% CH3OH). When used as the sensing electrode in amperometric detection in flow-injection analysis, the HCME permitted sensitive detection of hydrazine at 0.5 V. The limit of detection was 0.1 ng. The linear range was from 50 ng to 2.4-mu-g. The method is very sensitive and selective.

ELECTROCHEMICAL STUDY OF ISOPOLYOXOMETALLATES AND HETEROPOLYOXOMETALLATES FILM MODIFIED MICROELECTRODES .1. PRETREATMENT AND MODIFICATION OF THE MO80-26(4-) MODIFIED CARBON-FIBER MICROELECTRODE

In this paper the preparation of isopoly- and heteropolyoxometallates (IPA and HPA) thin film modified carbon fiber (CF) microelectrodes and the factor that influences the modification of IPA and HPA films are described. IPA and HPA film modified CF microelectrodes can all be prepared by cyclic potential scan and simple dip coating. The modified electrodes prepared are very stable and reversible in acidic solution with monolayer characteristics. The electrochemical pretreatment of CF microelectrodes plays an important role in the modification of IPA and HPA film. The absorption of IPA and HPA film on electrode surfaces has been discussed on the basis of surface conditions of the CF microelectrode and the structure of IPA and HPA.

EVALUATION OF THE EFFECT OF WAVELENGTH POSITIONING ERRORS ON KALMAN FILTERING RESULTS IN INDUCTIVELY COUPLED PLASMA ATOMIC EMISSION-SPECTROMETRY

This work evaluates the effect of wavelength positioning errors in spectral scans on analytical results when the Kalman filtering technique is used for the correction of line interferences in inductively coupled plasma atomic emission spectrometry (ICP-AES). The results show that a positioning accuracy of 0.1 pm is required in order to obtain accurate and precise estimates for analyte concentrations. The positioning error in sample scans is more crucial than that in model scans. The relative bias in measured analyte concentration originating from a positioning error in a sample scan increases linearly with an increase in the magnitude of the error and the peak distance of the overlapping lines, but is inversely proportional to the signal-to-background ratio. By the use of an optimization procedure for the positions of scans with the innovations number as the criterion, the wavelength positioning error can be reduced and, correspondingly, the accuracy and precision of analytical results improved.

LIQUID-CHROMATOGRAPHY WITH ELECTROCATALYTIC DETECTION OF CYSTEINE, N-ACETYLCYSTEINE AND GLUTATHIONE BY A PRUSSIAN BLUE FILM-MODIFIED ELECTRODE

Chemically modified electrodes prepared by adsorbing prussian blue on a glassy carbon electrode are shown to catalyse the electro-oxidation of cysteine, N-acetylcysteine and glutathione in acidic media. The catalytic response is evaluated with respect to the potential scan rate, the solution pH, the concentration dependence, and other variables. Covering the electrode with Nafion(R) film improved the stability and reproducibility in liquid chromatography with electrochemical detection to the extent that repetitive sample injections produced relative standard deviations of less than 5% over several hours of operation. The limit of detection was 4 pmol for cysteine, 33 pmol for glutathione and 61 pmol for N-acetylcysteine.

A MASS-SPECTROMETRIC STUDY OF ORGANIC PHOSPHORUS-COMPOUNDS .5. EI SPECTRA OF 1, 3, 2-OXAZAPHOSPHOLIDINE 2-SULFIDES DERIVATES

The mass spectral behaviour of 15 new type of organic phosphorus compounds with a considerable insecticidal activity, 1, 3,2-oxazaphospholidine 2-sulfides derivatives, under 70 eV electron impact has been studied by means of high and low resolution mass spectrometry as well as by B/E linked scan and MIKES/CID analysis. Discussion is focused into the isomerization between oxygen and sulphur in molecules and some rearrangement reactions.

A STUDY OF TETRAMETHYLAMMONIUM CATION ACROSS THE WATER-NITROBENZENE INTERFACE BY NEOPOLAROGRAPHY

The transfer behavior of tetramethylammonium cation (TMA~+) across the water/ nitrobenzene interface has been investigated by neopolarography including semiintegral (m), semidifferential (e), 1.5th order differential (e′) and 2.5 th order differential (e″) methods. The predicted dependences of peak height, peak potential and peak width on concentration and scan rate, etc have been discussed theoretically. The neopolarographic theory on the transfer of ions across the interface has been confirmed ...

Geomorphology, sedimentary processes and development of the Zenisu deep-sea channel, northern Philippine Sea

The Zenisu deep-sea channel originates on the Izu-Ogasawara island arc, and disappears in the Shikoku Basin of the Philippine Sea. The geomorphology, sedimentary processes, and the development of the Zenisu deep-sea channel were investigated on the basis of swath bathymetry, side-scan sonar imagery, submersible observations, and seismic data. The deep-sea channel can be divided into three segments according to the downslope gradient and channel orientation. They are the Zenisu Canyon, the E-W fan channel, and the trough-axis channel. The sediment fill is characterized by turbidite and debrite deposition and blocky-hummocky avalanche deposits on the flanks of the Zenisu Ridge. In the Zenisu Canyon and the Zenisu deep-sea channel, sediment transport by turbidity currents generates sediment waves (dunes) observed during the Shinkai 6500 dive 371. The development of the Zenisu Canyon is controlled by a N-S shear fault, whereas the trough-axis channel is controlled by basin subsidence associated with the Zenisu Ridge. The E-W fan channel was probably affected by the E-W fault and the basement morphology.

Characteristics of shallow gas hydrate in Okhotsk Sea

Multidisciplinary field investigations were carried out in Okhotsk Sea by R/V Akademik M.A. Lavrentyev (LV) of the Russian Academy of Sciences (RAS) in May 2006, supported by funding agencies from Korea, Russia, Japan and China. Geophysical data including echo-sounder, bottom profile, side-scan-sonar, and gravity core sample were obtained aimed to understand the characteristics and formation mechanism of shallow gas hydrates. Based on the geophysical data, we found that the methane flare detected by echo-sounder was the evidence of free gas in the sediment, while the dome structure detected by side-scan sonar and bottom profile was the root of gas venting. Gas hydrate retrieved from core on top of the dome structure which was interbedded as thin lamination or lenses with thickness varying from a few millimeters to 3 cm. Gas hydrate content in hydrate-bearing intervals visually amounted to 5%-30% of the sediment volume. This paper argued that gases in the sediment core were not all from gas hydrate decomposition during the gravity core lifting process, free gases must existed in the gas hydrate stability zone, and tectonic structure like dome structure in this paper was free gas central, gas hydrate formed only when gases over-saturated in this gas central, away from these structures, gas hydrate could not form due to low gas concentration.

栉孔扇贝(Chlamys farreri)Toll样受体及其信号传递相关基因的克隆与表达

扇贝是我国海水养殖的重要品种，但自1994年以来，养殖扇贝陆续爆发的大规模死亡，不但造成了巨大的经济损失，而且直接威胁到现有产业的生存和发展。引起扇贝大规模死亡原因是多方面的，其主要原因是养殖环境恶化、扇贝种质衰退和抗病力下降。因此，深入研究扇贝免疫防御机制，探讨提高机体抗病力的有效途径和方法，改良种质和培育抗病品系，无疑是解决目前困扰扇贝养殖业健康可持续发展的必经之路。 Toll样受体（TLRs）家族是新近发现的模式识别受体（PRRs），参与识别病原体相关的分子模式（PAMPs），在天然免疫系统中起着非常重要的作用。哺乳动物中Toll样受体信号通路还参与诱导树枝状细胞成熟、参与免疫耐受、参与凋亡发生发展、介导非感染性因素的识别等，被视为联系天然免疫和获得性免疫的桥梁。同时果蝇的Toll信号通路也是不具备获得性免疫的果蝇赖以抵御病毒、细菌和真菌感染，介导天然免疫反应的重要信号通路。 本研究采用大规模EST测序方法，结合Genome Walker库的构建和cDNA末端快速扩增技术，从栉孔扇贝克隆得到CfToll-1、CfMyd88、CfTRAF6和CfCactus这四个Toll样受体信号通路基因的全长cDNA，同时用荧光实时定量PCR技术检测了这些基因的组织分布及在脂多糖（LPS）和肽聚糖（PGN）刺激下的表达规律。 栉孔扇贝Toll样受体（CfToll-1）的cDNA序列全长4308 bp，包含5’非翻译区（UTR）211 bp，3597 bp的开放阅读框，500 bp的3’UTR，最后为18个腺嘌呤的ploy A 尾巴。开放阅读框编码1198个氨基酸的多肽，该多肽的估计分子量为137.41kd，估计的等电点为5.62，该多肽有信号肽，具有一个预测的跨膜区，因此是一种跨膜蛋白。经BLAST比对，CfToll-1基因与节肢动物多种Toll蛋白高度的相似性。SMART（Simple Modular Architecture Research Tool）软件分析，CfToll-1包含典型的Toll样受体的结构：富含亮氨酸的重复序列的胞外区（leucine-rich repeats, LRR），一段跨膜结构域，以及胞内区的TIR结构域（Toll/IL-1 receptor homologous region）。利用Real-time RT-PCR发现CfToll-1mRNA在扇贝体内普遍存在于血细胞、肌肉、外套膜、心、性腺和鳃组织中。利用体外培养的原代血细胞系研究不同浓度LPS刺激后CfToll-1的表达变化，结果显示低剂量（100ng.mL-1 ）LPS 使CfToll-1 mRNA表达量减小，该变化在1.5h、3h 和9h组差异显著，虽然在6h组表达量稍有恢复，但尚未达到对照水平；用1μg.mL-1LPS处理细胞时， 6h组CfToll-1表达量明显上调，约为对照水平的2倍。证实细菌结构脂多糖对CfToll-1基因的表达有影响，且这种影响有剂量依赖效应。 栉孔扇贝Myd88同源基因（CfMyd88）的cDNA序列全长1554bp，包含5’UTR 427 bp，1101bp的开放阅读框，最后为18个腺嘌呤的ploy A 尾。CfMyd88的开放阅读框可编码367个氨基酸的多肽，该多肽的估计分子量为42.37kD，估计的等电点为5.71。利用SMART程序分析发现CfMyd88编码了Death和TIR结构域, 这两个结构域是Myd88特征结构。BLAST程序发现扇贝的序列与数据库哺乳动物的Myd88基因高度同源。原代培养的扇贝血细胞在受到PGN刺激后，CfMyd88 mRNA表达在1.5小时开始下调，直到9小时下调至对照表达量的1/10，证实肽聚糖结构对CfMyd88基因的表达有影响。 栉孔扇贝TRAF6同源基因（CfTRAF6）的cDNA序列全长2510bp，包含5’UTR 337 bp，1965bp的开放阅读框，3’UTR 208bp，最后为21 个腺嘌呤的ploy A 尾巴。CfTRAF6开放阅读框编码655个氨基酸的多肽，该多肽的估计分子量为74.09kD，估计的等电点为6.01。InterPro Scan在线分析发现CfTRAF6有典型的TRAF蛋白家族的特征结构，包括的一个指环结构，两个锌指结构，一个MATH （the meprin and TRAF homology）结构域以及Coiled-coil区域。CfTRAF6的序列与数据库多物种的TRAF6高度同源，同源性最高的是乌贼序列（Identity＝68）和鼠类（Identity＝45%）。利用Real-time RT-PCR，发现CfTRAF6在各组织普遍存在，在性腺中的表达最高。原代培养的扇贝血细胞在受到不同浓度PGN刺激后，与CfMyd88的情况一样，CfTRAF6的表达量变化减少，且这种变化随剂量的增加更加明显。 栉孔扇贝Cactus同源基因（CfCactus）的cDNA序列全长2488bp，包含5’UTR 181 bp，840bp的开放阅读框， 3’UTR 1467bp，最后为19个腺嘌呤的ploy A 尾巴。CfCactus的开放阅读框编码279个氨基酸的多肽，该多肽的估计分子量为31.37 kD；估计的等电点为4.74，与果蝇的Cactus基因的等电点相近（4.5）。利用SMART程序分析发现CfCactus主要编码了ANK结构域（ankyrin repeats）。Cactus基因为哺乳动物NF-κB抑制蛋白IκB的同源分子，BLAST 程序发现扇贝的序列与数据库多物种的Cactus或IκB基因高度同源。同源性最高的是太平洋牡蛎（Identity=35%）和圆尾鲎（Identities = 44%）。对CfTCactus mRNA在扇贝的血细胞、性腺、 肠的组织表达进行分析，并同时与CfTRAF6和CfMyd88的表达量进行了对比，发现CfCactus的表达水平明显高于这两个基因，而且CfTRAF6的基因表达量也高于CfMyd88，表现出级联放大效应。正常情况下，三个基因在性腺的表达量最高，推测这条通路可能和发育等功能密切相关。 通过本研究我们首次在双壳类软体动物找得到与果蝇Toll蛋白家族高度同源的CfToll-1基因，同时发现其他三个在Toll样受体信号传递过程中起重要作用的基因，其中包括在软体动物中获得的第一个Toll样受体的接头分子－CfMyd88基因，该结果直接证明软体动物具有与哺乳动物和节肢动物高度类似Myd88依赖的Toll样受体信号通路。同时通过这些基因组织分布的研究以及细菌结构LPS和PGN对这条通路上基因表达的影响，证明扇贝Toll信号通路可能与在果蝇中一样，参与扇贝的发育和免疫防御等多种功能。