锌离子在水相介南Zn／V2O5二次电池中的迁移性能研究

利用间歇性恒电流测定法和Ｘ－Ｒａｙ衍射法，研究水相介质的Ｚｎ／Ｖ２Ｏ５二次电池中的锌离子在正材料中的迁移性能及其放电机理；讨论锌离子正极材料中发生迁移时的某些动力学参数与放电深度的关系，实验结果表明，该电池的正极放电反应为锌离子在ＺｎｘＶ２Ｏ５中的嵌入过程。     

锌离子在水相介质Zn/V_2O_5二次电池中的迁移性能研究

利用间歇性恒电流测定法和Ｘ Ｒａｙ衍射法,研究水相介质的Ｚｎ／Ｖ２Ｏ５二次电池中的锌离子在正极材料中的迁移性能及其放电机理;讨论锌离子在正极材料中发生迁移时的某些动力学参数与放电深度的关系．实验结果表明,该电池的正极放电反应为锌离子在ＺｎｘＶ２Ｏ５中的嵌入过程．     

恒电位氟-铝配位滴定法测定铝的研究

以氟离子溶液作滴定剂,氟离子选择性电极作指示电极,对恒电位配位滴定法测定铝进行了研究,导出了该测定法的计算模型。测定结果的准确度受电位的控制误差对滴定剂体积误差的影响及滴定剂体积的相对误差两个因素影响。在滴定的中间位置,准确度比较高。随着滴定剂体积的增加,测定的灵敏度增加。方法可用于金属铝及锌一铝合金中铝的测定。     

5-Br-PADAP作为锌的络合滴定指示剂的研究

5-Br-PADAP是分光光度法测定锌高灵敏度的显色剂,现已用于矿石、合金中锌的测定。但采用5-Br-PADAP作为锌的络合滴定指示剂还未见报道。我们在实验中发现,PH4.5乙酸-乙酸钠介质中,采用5-Br-PADAP,以EDTA络合剂进行滴定,溶液颜色由紫红色变为亮黄色、终点突跃非常敏锐,准确度高。本文研究了以5-Br-PADAP为指示剂、EDTA络合滴定锌的条件及共存离子的影响,并应用拟定的方法测定矿石中的锌,得到了满     

铝,镁,锌—氟哌酸配合物的荧光特性及其脂溶性研究

探讨了介质ＰＨ值及Ａｌ＾３－，Ｍｇ＾２＋，Ｚｎ＾２＋离子对喹诺酮类药物氟哌酸荧光特性的影响。发现铝，镁及锌离子在不同ＰＨ值条件下与氟哌酸形成配合物而增强荧光，据此建立了用铝离子增强荧光测定氟哌酸含量的新方法。     

5－Br－PADAP作指示剂络合滴定法连续测定矿石中的锌和铜

本文在ｐＨ５．５的乙酸－乙酸钠介质中，对以５－Ｂｒ－ＰＡＤＡＰ作指示剂络合滴定法连续测定锌和铜进行了研究，对滴定的ｐＨ值及指示剂用量进行了选择，试验了锌、铜不同配比的滴定结果，研究了共存离子的干扰。实验表明，用５－Ｂｒ－ＰＡＤＡＰ作指示剂、ＥＤＴＡ作滴定剂连续测定锌和铜，滴定终点颜色变化敏锐，准确度高，锌和铜均在０～２０ｍｇ范围内与ＥＤＴＡ用量成正比，锌、铜比例在１：１０～１０：１范围内相互无影响，方法用于标样及金矿中锌、铜的连续测定，结果满意。     

离子对高效液相色谱分离及光度检测法测定meso-四(4-甲基-3-磷酸苯基)卟啉-铜、锌络合物

报道了ｍｅｓｏ－四（４－甲基－３－磺酸苯基）卟啉［Ｔ（４－ＭＰ）ＰＳ４］作柱前衍生试剂生成铜、锌络合物，四乙基碘化胺（ＴＥＡ·Ｉ）为离子对试剂。离子对高效液相色谱及光度检测快速分离测定铜、锌的方法。流动相为乙腈＋水，内含乙酸．乙酸钠缓冲液和四乙基碘化胺。方法具有较高的灵敏度和选择性，并用于测定莲子和花生等食品中的痕量铜和锌。     

Cyanex272—Span80—甲苯乳状液膜迁移分离锌,镉及其它元素…

用Ｃｙａｎｅｘ２７２－Ｓｐａｎ８０－甲苯乳状液膜研究了Ｚｎ＾２＋的迁移行为，在适宜条件下，５ｍｉｎ内锌的迁移率达９５％以上，而在此条件下，与锌性质相近的镉、铜、钴、镍、汞等金属离子不迁移或迁移率很低。因此，用此乳状液膜体系可将锌与镉及其它常见离子分离。     

7－（4，5－二甲基－2－噻唑偶氮）－8－羟基喹啉与锌显色反应的研究和应用

探讨题示试剂（ＤＭＴＡＱ）与锌离子的显色反应条件，当ｐＨ为５．５，在ＴｒｉｔｏｎＸ－１００存在下，ＤＭＴＡＱ与锌离子形成红色配合物，最大吸收峰位于５４５ｎｍ，表观摩尔吸光系数９．４×１０￣４Ｌ·ｍｏｌ￣（－１）·ｃｍ￣（－１），锌量在０～２５μｇ／５０ｍＬ范围内符合比尔定律。该法可用于测定人发中的微量锌。     

六氨合钴离子交换法测定粘土中阳离子交换容量

六氨合钴离子「Ｃｏ（ＮＨ３）６」＾３＋具有与粘土中主要阳离子（Ｃａ＾２＋、Ｍｇ＾２＋、Ｋ＾＋、Ｎａ＾＋、Ｈ＾＋等）交换的能力。稳定性好,并在４７４ｎｍ处有最大吸收。利用分光光度法,以「Ｃｏ（ＮＨ３）６」＾３＋作为交换离子,测定阳离子交换容量。试验表明,在ＰＨ７－８,常温条件下７ｈ交换达到平衡;在８０℃时３ｈ可以达到平衡。粘土中共生的非粘土矿物、游离金离离子不干扰其测定。用该法测得的阳离子交换容量值与氯化铵溶液法,盐基分是测定法测得的结果一致。     

Amplified Detection of NAD+ and NADH by the Enzymatic Cycling with the Use of Immobilized Enzymes in a Flow System

Abstract

The enzymatic cycling for the detection of NAD⁺ and NADH in low level was carried out in the flow system with immobilized enzymes. Alcohol dehydrogenase and glutamate dehydrogenase immobilized on Sepharose 4B were used for the cycling reaction. The compound produced in the enzymatic cycling reaction was subjected to an enzymatic reaction to yield NADH, which was detected fluorometrically.     

酶法测定乙醛

乙醛作为化工原料 ,其工业废水若处理不当 ,将造成天然水系的污染 ,因此 ,乙醛是环境监测的一项重要指标 .测定方法主要有碘量法 ,色谱法 ,光度法 ,及化学发光法等 [1 ,2 ] ,近年来酶法在分析测定方面得到广泛应用 ,以酶法测定食品中乙醛含量已有报道 [3] .本文基于乙醛 NADH(还原型烟酰胺腺嘌呤二核苷酸 ) 乙醇 NAD (氧化型烟酰胺腺嘌呤二核苷酸 )在2 5℃时 ,反应平衡常数为 1 .0× 1 0 1 1 ,反应平衡偏向生成乙醇的方向 ,因此有利于痕量乙醛的测定 .通过在醇脱氢酶存在下 ,NADH→NAD 的转化 ,测定 NADH吸光度的变化率 ,得出其…     

酶法测定乳酸

利用乳酸在氧化型烟酰胺腺嘌呤二核苷酸（NAD）存在的条件下,由乳酸脱氢酶（L-LDH）催化生成丙酮酸和还原型烟酰胺腺嘌呤二核苷酸（NADH）。通过测定NADH吸光度的变化率可得出乳酸的酶促反应速度,并制得标准曲线。样品中的乳酸可由标准曲线求得。讨论了试剂用量、pH、温度和共存离子对测定的影响。     

酶催化动力学荧光法测定乙醇

利用醇脱氢酶(ADH)催化乙醇与氧化型烟酰胺腺嘌呤二核苷酸(NAD)反应的原理,通过测定还原型烟酰胺腺嘌呤二核苷酸(NADH)荧光强度的变化率得出其酶促反应速度,对应乙醇浓度而制得标准曲线,试样中乙醇含量由标准曲线求得,检出限为4.0×10-6mol/L。考察了试剂用量、pH、共存组分对测定的影响。该方法简便、快速、准确。     

Amperometric determination of lactate dehydrogenase based on a carbon fiber microcylinder electrode modified covalently with Toluidine Blue O by acylation

A method has been developed for the modification of a carbon fiber microcylinder electrode with acylation. The stability and surface coverage of the Toluidine Blue O-modified microelectrode were studied by cyclic voltammetry. The modified electrode showed significant activity for the electrocatalytic oxidation of NADH in pH 6.8-7.8 solution. The catalytic current increased linearly with increasing concentration of NADH from 4.0 x 10(-5) to 1.5 x 10(-3) M. A simple amperometric determination based on electrochemical detection of NADH produced from the enzymatic reaction of lactate with NAD(+) under the catalysic effect of lactate dehydrogenase (LDH) is reported. The experimental factors which had primary influence on the analytical performance were studied. The sensor had a linear response over a range of LDH concentrations from 5.0 U l(-1) to 200 U l(-1) at -0.2 V vs. SCE under optimum conditions. A satisfactory result was obtained for the determination of LDH in clinical blood samples.     

Molecular dynamics simulation study on stabilities and reactivities of NADH cytochrome B5 reductase

Binding free energies between coenzyme (FAD and NADH) and the apoenzyme of NADH-cytochrome b5 reductase (b5R) were estimated by applying the continuum Poisson-Boltzmann (PB) model to structures sampled from molecular dynamics simulations in explicit water molecules. Important residues for the enzymatic catalysis were clarified using a computational alanine scanning method. The binding free energies calculated by applying an alanine scanning method can successfully reproduce the trends of the measured steady-state enzymatic activities kcatNADH/KmNADH. Significant decreases in the binding free energy are expected when one of the four residues Arg91, Lys110, Ser127, and Thr181 is mutated into Ala. According to the results of the molecular dynamics simulation, Thr181 is considered to be one of the key residues that helps NADH to approach the isoalloxazine in FAD. Finally, we have constructed very simplified model systems and carried out density functional theory calculations using B3LYP/LANL2DZ//ROHF(or RHF)/LANL2DZ level of theory in order to elucidate a realistic and feasible mechanism of the hydride-ion transfer from NADH to FAD affected by HEME(Fe3+) as an electron acceptor. Our calculated results suggest that the electron and/or hydride-ion transfer reaction from NADH to FAD can be accelerated in the presence of HEME(Fe3+).     

Selective Enzymatic Determination of L-Phenylalanine and Phenyl-Pyruvate

Abstract

A simple enzymatic end point method for the determination of L-phenylalanine and 3-phenylpyruvate has been developed. The assay is based on the spectrophotometry determination of NADH formed or degraded in the reaction catalyzed with Thermoactinomyces intermedins phenylalanine dehydrogenase. This method enables the simple and selective determination of L-phenylalanine and 3-phenylpyruvate based on the high substrate specificity of the enzyme. The assay is sensitive in the range of 0.015?0.15 umol of L-phenylalanine and 3-phenylpyruvate.     

An Enzymatic Microdetermination Method for Hydroxylase Cofactor

Abstract

An enzymatic microdetermination method is described to determine the concentration of biologically active hydroxylase cofactor in crude samples. A small amount of hydroxylase cofactor was oxidized and reduced in a cyclic fashion by phenylalanine 4-monooxygenase (EC 1.14.16.1, PheOHase) and dihydropteridine reductase (EC 1.6.99.7, DPRase) in the presence of excess phenylalanine (Phe) and NADH. The amount of NAD⁺, accumulated as a result of this cyclic reaction (first cycling), was in proportion to that of the hydroxylase cofactor. The NAD⁺ was further amplified by an enzymatic amplification reaction, NAD cycling (second cycling) and determined fluorometrically. This double cycling method with more than a 20,000 fold amplification provided extremely high sensitivity, down to 0.02 pmol per assay, and was successfully applied to crude microsamples of pg wet weight.     

A new kinetic method for quantification phenoxyl free radicals

In this work, a new kinetic method was proposed for quantification phenoxyl radicals generated in enzyme reaction. Instead of direct detecting the spectral signals of phenoxyl radicals, a molecular probe, the reduced form of nicotinamide adenine dinucleotide (NADH), was employed to indicate the formation of phenoxyl free radicals. It was found that the reactions of NADH and phenoxyl radicals are very fast, but can be followed by using stopped-flow fast scanning spectrophotometric technique. The initial rate of accelerated-oxidation of NADH represents the reactivity of phenoxyl free radical, which is proportional in a certain range to the initial concentration of the parent chlorophenols of the radicals. With this method, the phenoxyl radicals generated in oxidation reaction of chlorophenols (2-CP; 4-CP; 2,4-DCP; 2,4,6-TCP and 2,3,4,6-Tetra-CP) with hydrogen peroxide, catalyzed by horseradish peroxidase, were investigated. The method is highly sensitive. Phenoxyl radicals generated from as low as 1 × 10⁻⁸ M 2,4-DCP, for example, can be readily detected with the proposed method. The results show that the reactivity of various phenoxyl radicals are in the following order: 2,4-DCP > 4-CP > 2-CP > 2,4,6-TCP > 2,3,4,6-Tetra-CP. A mechanism is proposed to explain the possible pathway of the probe reaction. The feasibility of this method was assessed by the determination of enzymatic generation of phenoxyl radicals in lake water samples.