Characterization and Potential Applications of Immobilized Glucose Oxidase and Polyphenol Oxidase

Pyrrole functionalized polystyrene (PStPy) was copolymerized with pyrrole to obtain a conducting copolymer, P(PStPy‐co‐Py) which is used as the immobilization matrix. Glucose oxidase and polyphenol oxidase enzymes were immobilized via the entrapment method by electrochemical polymerization. Enzyme electrodes were prepared by electrolysis at a constant potential using sodium dodecyl sulfate (SDS) as the supporting electrolyte during the copolymerization of PStPy with pyrrole. Maximum reaction rates (V_max) and enzyme affinities (Michaelis‐Menten constants, K_m) were determined for the enzyme entrapped both in polypyrrole (PPy) and P(PStPy‐co‐Py) matrices. Optimizations of enzyme electrodes were done by examining the effects of temperature and pH on enzymes' activities along with the shelf life and operational stability investigations. Glucose oxidase enzyme electrodes were used for human serum analysis and glucose determination in two brands of orange juices. Polyphenol oxidase enzyme electrodes were used for the determination of phenolics in red wines of Turkey.     

基于硅溶胶-凝胶/褐藻酸钠复合膜包埋酪氨酸酶的苯酚传感器研制

将天然聚合物褐藻酸钠添加到无机硅溶胶-凝胶膜,获得一种新型的无机/有机杂化膜。用此杂化膜包埋酪氨酸酶,制备电化学苯酚传感器。研究表明:硅溶胶-凝胶/褐藻酸钠复合膜能有效克服纯无机溶胶-凝胶膜的脆性;避免膜的裂开;提供生物酶所适宜的微环境;有效保持所固定酶的生物活性。所制备的传感器测定苯酚的线性响应范围为3.4-93.1μmol/L,其线性回归方程i(μA)=0.0774C(μmol/L) 0.1616,r=0.9980。检出限为1.33μmol/L。     

Ortho-Hydroxylation of Phenol by Tyrosinase Model Compounds

A series of tyrosinase model ligands and complexes containing polyimidazoles were prepared. 2, 4-Di-tert-butyl-phenol was ortho-hydroxylated by the binuclear copper (I) complex [Cu2(6a)(CH3CN)2](ClO4)2 8a and molecular dioxygen under mild conditions with up to 80.4% yield, 91.4% selectivity and 92.0% conversion.     

Determination of Oxalate with Immobilized Oxalate Oxidase in an Enzyme Thermistor

Abstract

This paper describes a rapid enzymic procedure, based on calorimetry, for specific determination of oxalic acid. Oxalate is oxidized by immobilized oxalate oxidase to hydrogen peroxide and carbon dioxide. The heat generated by this reaction is measured in a calorimetric device, the enzyme thermistor. Oxalate concentrations as low as 0.02 mM can be determined. Also described is purification and immobilization of the enzyme, as well as the effect of some of its inhibitors. The urinary oxalate content of 16 persons was determined using the enzyme thermistor. For samples containing a very low concentration of oxalate (less than 0.2 mM) an extraction step with tributylphosphate can be introduced to purify and concentrate the oxalate. The oxalate content in different kinds of food was also determined.     

开管柱固定化葡萄糖氧化酶反应器的制备及其在流动注射分析中的应用

本文将葡萄糖氧化酶化学键合到粗糙化的玻璃毛细管内壁上,用开管柱固定化酶反应器-安培检测器进行葡萄糖的流动注射分析。讨论了流速对流动注射分析体系峰电流和分散度的影响,提出了测量开管柱固定化酶表观活力的方法。     

壳聚糖-（4-叔丁基邻苯二酚）的酪氨酸酶催化接枝初探

以自制马铃薯酪氨酸酶催化氧化4-叔丁基邻苯二酚成活性邻醌,后与壳聚糖接枝反应,并着重探讨了反应条件对接枝率的影响。通过红外光谱对该反应产物进行结构的初步表征,结果表明酶催化接枝反应的适宜条件为：4-叔丁基邻苯二酚浓度3．0mmol／L、酶活力20U／mL、反应时间30min、壳聚糖溶液百分含量0．5％;用线性电位滴定法测定其接枝率为37％～64％。     

溴化衍生气相色谱法测定环境水体中痕量苯酚

以溴水为衍生化试剂,使苯酚转化为三溴酚。选择抗坏血酸为稳定剂,甲苯为萃取剂,以ＦＦＡＰ或ＳＥ－３０大口径石英毛细管柱及电子俘获检测器,采用气相色谱方法测定环境水体中痕量苯酚。本方法操作简便、灵敏度高,选择性好,线性范围宽。检测限为０．０１μｇ／Ｌ;水样添加回收率为９５％－１０２％;相对标准偏差１．６％;工作曲线的线性范围为０．０１－４０μｇ／Ｌ。本方法与目前国家饮用水质标准中苯酚的标准检测方法比较     

聚苯胺葡萄糖氧化酶电极的催化过程

用电化学方法固定在直径为0.5mm铂丝上的聚苯胺(PANI)葡萄糖(GOD)电极对葡萄糖有催化氧化作用.在0～-0.6V(vs.SCE)的电极范围内,在电极的循环伏安曲线上观察到与葡萄糖浓度有关的氧的还原峰和GOD还原态的氧化峰,用此GOD还原态的氧化峰电流可定量检测葡萄糖的浓度。本文提出在PANI电极上存在着酶反应氧化还原电荷直接传递的可能性。     

多波长线性回归荧光法同时测定苯酚,间苯二酚和间苯三酚

酚类物质是环保、卫生、医药、食品等行业分析的重要指标，通常只能测定酚的总量［１～３］，最小二乘法［４］、卡尔曼滤波法［５］虽能同时测定各量，但需要用计算机解谱，且只进行了苯酚和间苯二酚两组分的测定．对于结构相似的苯酚、间苯二酚和间苯三酚三组分混合体系...     

鲁米诺-高锰酸钾-苯酚化学发光体系研究

基于鲁米诺-高锰酸钾-苯酚体系很好的化学发光特性,建立一种测定苯酚的流动注射化学发光分析新方法。在最优化实验条件下,苯酚浓度在0．001—2．5mg／L范围内与化学发光强度呈良好的线性关系,标准曲线为ΔI=750．45C(mg／L) 1．4655(n=8,r^2=0．9998),检出限(3σ)为0．35μg/L;对0．05和0．5mg／L的苯酚进行11次平行测定,相对标准偏差(RSD)分别为0．6％和2．5％。应用本法于合成样品和工业废水中苯酚的测定,结果令人满意。     

儿茶酚在预活化聚酰胺膜多酚氧化酶电流传感器上的响应特性

本采用预活化聚酰膜固定多酚氧化酶并与浸蜡石墨极组合成传感器，测定儿茶酚的线范围２．×１０－７－１．２５×１０＾－５ｍｏｌ／Ｌ。检出限１．５×１０＾－７ｍｏｌ／Ｌ。酶的固定时间仅需１－２ｍｉｎ，５个月之后被固定酶的活性未见下降，活性酶膜的制备，贮存，替换均很方便，对传感器的机理进行了探讨。     

Adsorptive Stripping Voltammetric Determination of Phenol at an Electrochemically Pretreated Carbon-Paste Electrode with Solid Paraffin as a Binder

An adsorptive stripping voltammetric method for determination of phenol at an electrochemically pretreated carbon-paste electrode has been developed. Solid paraffin was used as the binder of the carbon-paste electrode. The carbon-paste electrode was pretreated in the solution of 0.001 mol L⁻¹NaOH by holding it at +1.8 V (versus an Ag/AgCl electrode) for 5 min. On the pretreated electrode, the adsorption of phenol was greatly enhanced. Phenol was accumulated in NH₃–NH₄Cl (pH 9.25) medium at the potential of +0.1 V (versus Ag/AgCl electrode) for a certain time and then determined by second order differential anodic stripping voltammetry. An oxidative peak was observed at about +0.66 V. The relationship between second order peak current and phenol concentration was linear in the range of 2.5 × 10⁻⁷–5.0 × 10⁻⁶mol L⁻¹phenol, and the detection limit was 5.0 × 10⁻⁸mol L⁻¹. The method has been applied to the determination of phenol in tap water and waste water. The relative standard deviation (six determinations) was less than 3.5%.     

流动注射-分光光度法测定天然产物对酪氨酸酶活性的影响

建立了一种快速、灵敏且高精度的流动注射-分光光度法用于研究天然产物对酪氨酸酶活性的影响。此方法基于一定介质条件下L-3,4-二羟基苯丙氨酸(L-DOPA)在酪氨酸酶的作用下,发生氧化生成棕褐色多巴醌,其最大吸收峰位于475 nm处,而酪氨酸酶抑制剂能降低酶促反应速度,减少多巴醌形成的量,从而降低475 nm下的吸光度值,形成倒峰。在优化实验条件下,半抑制浓度的曲酸抑制酪氨酸酶活性测定相对标准偏差(n=10)为0.036%,与分光光度法和酶标仪微量法相比,精密度提高了10倍以上。咖啡酸对酪氨酸酶有较强的激活作用,对二酚酶相对激活率达到50%时的浓度(IC50)为0.170 mmol/L;薰衣草花水相提取物具有较强的抑制活性,其IC50值为0.96 mg/m L。与分光光度法及酶标仪微量法相比,流动注射-分光光度法精密度高,重复性好,适用于天然产物对酪氨酸酶活性影响的测定。     

酪氨酸酶催化下以吡啰红为指示剂荧光测定青蒿素

Fluorescence decrease ratio （F0/F） was applied to determination of artemisinin （qinghaosu, QHS） based on the catalytic effect of tyrosinase using tetraethyldiaminoxanthenyl chloride （pyronine B, PB） as monitor. A catalyst used commonly in the decomposition of QHS, tyrosinase, exhibited higher binding activity than hemin, which was expressed as Michaelis-Menten parameters, km, Vmax, and kcat respectively. Interaction of QHS with tyrosinase was inhibited in the presence of deactivating agents at high temperature whereas enhanced by ethanol. Under optimal conditions, a concentration of 1.4×10^-7-8.4×10^-7 mol·L^-1of QHS could be determined on the basis of fluorescence decrease ratio of PB, with a detection limit 3tr of 2.6×10^-9 mol·L^-1. The proposed method was applied to detection of the concentration of QHS in the media of plasma and urine.     

Sensitive and Selective Spectrophotometric Determination of Para- and Ortho- Aminophenol with Hypochlorite-Alkaline Phenol (Berthelot) Reagents

Abstract

A highly selective and sensitive method is described for the determination of para- as well as ortho-isomers of aminophenol. The method involves oxidative coupling of aminophenol with Berthelot hypochlorite-alkaline phenol reagents. The reaction yielded a blue chromophose with p-aminophenol (∑=10,000 at 633 nm) and a dark green chromophore with o-aminophenol (∑=1436 at 845 nm). The reaction mechanisms involved in the chromophore formation are discussed.     

Spectrometric Determination of Ti(IV) With an Azopyrazolonic Derivative

Abstract

Spectrometric studies on the complexation of Ti(IV) with a new organic reagent obtained by coupling 3-methyl-1-phenyl-5-pyrazolone with diazotized 3-amino-4-hydroxy-benzene-sulphonic acid were carried out.

A 1:2 Ti(IV):reagent complex, which is soluble in water, is formed at pH 5–6.2. The maximum absorbance of the complex lies at λ =520nm, where the absorbance of the reagent is very low. The molar absorptivity at this wavelength is 5 × 10³ L mol^?1 cm^?1; the value of log K is 8.0 ± 0.2. at 20 ± 1°C and pH=5.6.     

Amperometric Tyrosinase Biosensor Based on Carbon Black Paste Electrode for Sensitive Detection of Catechol in Environmental Samples

In this work, a renewable tyrosinase-based biosensor was developed for the detection of catechol, using a carbon black paste electrode, without any mediator. The effect of pH, type of electrolyte, and amount of tyrosinase enzyme were explored for optimum analytical performance. The best-performing biosensor in amperometric experiments at potential −0.2 V vs. Ag/AgCl (3 mol L⁻¹ KCl) was obtained using a 0.1 mol L⁻¹ phosphate buffer solution (pH 7.0) as electrolyte. Under optimized conditions, the proposed biosensor had two concentration linear ranges from 5.0×10⁻⁹ to 4.8×10⁻⁸ and from 4.8×10⁻⁸ to 8.5×10⁻⁶ mol L⁻¹ and a limit of detection of 1.5×10⁻⁹ mol L⁻¹. The apparent Michaelis-Menten constant ( ) was calculated by the amperometric method, and the obtained value was 1.2×10⁻⁵ mol L⁻¹ whose result was similar when compared with other studies previously. The biosensor was applied in river water samples, and the results were very satisfactory, with recoveries near 100 %. In addition, the response of this biosensor for different compounds, taking into account their molecular structures was investigated and the results obtained showed no interference with the response potential of catechol. The electrochemical biosensor developed in this work can be considered highly advantageous because it does not require the use of a mediator (direct detection) for electrochemical response, and also because it is based on a low-cost materials that can be used with success to immobilise other enzymes and/or biomolecules.     

用聚吲哚乙酸修饰电极测定肾上腺素

报道了聚吲哚乙酸修饰电极的制备，并研究了肾上腺素在该修饰电极上的循环伏安特性及测定方法。实验表明，在ＰＨ７．０的磷酸盐缓冲溶液中，用该电极测定肾上腺素的线性范围为１．０＊１０＾－７－６．０＊１０＾－６ｍｏｌ／Ｌ，检出限为４．０＊１０＾Ｔ－８ｍｏｌ／Ｌ。将此法用于药剂中肾上腺素的测定，结果满意。