Reagentless lactate electrodes based on electrocatalytic oxidation of flavocytochrome b2

Flavocytochrome b₂ (L-lactate :cytochrome c reductase, E.C. 1.1.2.3) from Hansenula anomala was entrapped on the surface of electrodes modified with various kinds of carbon black. The electrocatalytic oxidation of a reduced enzyme by the electroactive surface groups of carbon black enables this enzyme electrode to be used for the determination of lactate. The electrodes operate at ?0.2 to ?0.1 V vs. SCE (pH 7.0), which is low enough to avoid interference from ascorbic acid. Linear calibration graphs up to 0.5 mM lactate were obtained. Electrochemical measurements of lactate in human blood plasma and cell culture fluids showed good agreement with the results of spectrophotometric measurements.     

Electrochemical microbioassay of vitamin b1

A microbioassay of vitamin B₁ is possible with a new electrode assembly consisting of a platinum anode and a silver peroxide cathode. The response time of the electrode decreases with increasing amount of the bacterial suspension (L. fermenti) injected. A linear relationship is obtained between the steady-state current and the concentration of vitamin B₁ in the culture broth. The microbioassay can be completed within 6 h, with relative errors of ±8%. A possible mechanism of the current generation is discussed.     

The effects of the 1b1 molecular orbital on the geometry of AH2 systems

Possible effects of the 1b₁ molecular orbital on the shapes of the first- and second-row AH₂ systems have been studied using the CNDO/2 method. The effects are shown to be small except for a few exceptional cases.     

Nonenzymatic electrochemical glucose sensor based on MnO2/MWNTs nanocomposite

In this communication, an amperometric glucose biosensor based on MnO₂/MWNTs electrode was reported. MnO₂ was homogeneously coated on vertically aligned MWNTs by electrodeposition. The MnO₂/MWNTs electrode displayed high electrocatalytic activity towards the oxidation of glucose in alkaline solution, showing about 0.30 V negative shift in peak potential with oxidation starting at ca. −0.20 V (vs. 3 M KCl–Ag/AgCl) as compared with bare MWNTs electrode. At an applied potential of +0.30 V, the MnO₂/MWNTs electrode gives a linear dependence (R = 0.995) in the glucose concentration up to 28 mM with a sensitivity of 33.19 μA mM⁻¹. Meanwhile, the MnO₂/MWNTs electrode is also highly resistant toward poisoning by chloride ions. In addition, interference from the oxidation of common interfering species such as ascorbic acid, dopamine, and uric acid is effectively avoided. The MnO₂/MWNTs electrode allows highly sensitive, low-potential, stable, and fast amperometric sensing of glucose, which is promising for the development of nonenzymatic glucose sensor.     

A cataluminescence gas sensor based on nanosized V2O5 for tert-butyl mercaptan

This work proposed a gas sensor for the determination of tert-butyl mercaptan, one of the highly toxic volatile sulfur compounds, which was based on cataluminescence emission during its catalytic oxidation on the surface of nanosized V₂O₅. The cataluminescence characteristics and the optimum conditions, including the morphology of sensing material, the wavelength of cataluminescence emission, the oxygen flow rate and working temperature were investigated in detail. Under the optimized conditions, the calibration curve of the relative cataluminescence intensity versus the concentration of tert-butyl mercaptan vapor was made, with the linear range of 5.6-196 μg mL⁻¹ and the detection limit of 0.5 μg mL⁻¹ (S/N = 3). The relative standard deviation (R.S.D.) (n = 5) of relative cataluminescence intensity for 84 μg mL⁻¹ tert-butyl mercaptan was 3.6%. There is no or weak response to some common substances, such as formic acid, alcohol (methanol, ethanol, propanol, isopropanol, n-butanol, isoamyl alcohol), o-dichlorobenzene, acetonitrile, ethyl acetate, aldehyde (formaldehyde, acetaldehyde and propanal), 1,2-dichloroethane and ammonia. Furthermore, the proposed sensor was successfully used for determining tert-butyl mercaptan in four artificial samples, with a good recovery. The results demonstrated that the proposed gas sensor had a promising capability for the tert-butyl mercaptan in routine monitoring.     

基于纳米ZnO-ZrO2催化发光丙酮传感器的研究

研究了丙酮在纳米ZnO-ZrO2(质量比为4:1)表面催化发光行为,发现基于这种纳米催化剂的气体传感器对丙酮的检测具有高灵敏度和较强的选择性。在波长460 nm,温度219℃,载气流速25 mL/min时进行定量分析,催化发光强度与丙酮浓度在一定范围内呈良好的线性关系,线性范围为0.1～4000 mL/m3(r=0.9996,n=6);检出限为1.6 mL/m3(S/N=3)。传感器工作时间可达106h以上,可用于丙酮的实时在线检测。     

A novel nonenzymatic hydrogen peroxide sensor based on MnO2/graphene oxide nanocomposite

A new electrocatalyst, MnO₂/graphene oxide hybrid nanostructure was successfully synthesized for the nonenzymatic detection of H₂O₂. The morphological characterization was examined by scanning electron microscopy and transmission electron microscopy. The MnO₂/graphene oxide based electrodes showed high electrochemical activity for the detection of H₂O₂ in alkaline medium. The nonenzymatic biosensors displayed good performance along with low working potential, high sensitivity, low detection limit, and long-term stability, which could be attributed to the high surface area of graphene oxide providing for the deposition of MnO₂ nanoparticles. These results demonstrate that this new nanocomposite with the high surface area and electrocatalytic activity offers great promise for new class of nanostructured electrode for nonenzymatic biosensor and energy conversion applications.     

A high-efficient amperometric hydrazine sensor based on novel electrospun CoFe2O4 spinel nanofibers

HeterojunctionFe_2O_3 nanoparticles(NPs), NiFe_2O_4 nanofibers(NFs), and CoFe_2O_4 NFs were synthesized by electrospinning and the subsequent thermal treatment processes. Characterization results indeed display the three-dimensional net-like textural structures of these as-electrospun spinel-type MFe_2O_4 NFs. The MFe_2O_4 NFs-based film configurations possess abundant micro/meso/macropores on their surface. These structures could afford more accessible transport channels for effective reduction of the mass transport resistance and improvement of the density of exposed catalytic active sites. All these advantages are responsible for the enhanced electro-catalytic performance of these MFe_2O_4 NFs in hydrazine oxidation. When used for hydrazine detection, CoFe_2O_4 NFs show the best catalytic efficiency.For example, the CoFe_2O_4 NFs possess a large sensitivity of 1327 mA cmà2(mmol Là1[à1in the linear range of 0.01 to 0.1 mmol Là1and 503 mA cmà2(mmol Là1)à1in the linear range of 0.1 to 11 mmol Là1, a response time of shorter than 3 s, good reproducibility and remarkable long-term stability. The superior catalytic efficiency, excellent stability, low cost, and ease of fabrication render CoFe_2O_4 NFs very promising materials in developing an electrochemical device that directly detects hydrazine.     

Ascorbic acid sensor based on ion-sensitive field-effect transistor modified with MnO2 nanoparticles

An ascorbic acid (AA) sensor based on an ion-sensitive field-effect transistor (ISFET) was prepared by modifying the sensitive area of the transducer with MnO₂ nanoparticles. An additional Nafion membrane coated on top of the sensor was used to immobilize the MnO₂ nanoparticles and restrict the amount of ascorbic acid entering the membrane. The reaction of the MnO₂ nanoparticles with ascorbic acid produced a local pH change, which was correlated with the ascorbic acid concentration and could be monitored by the ISFET. The linear range of the ascorbic acid sensor was 0.02-1.27 mM, and the detection limit was 0.01 mM. The effects of buffer concentration, pH, and ionic strength on the sensor performance were also examined. In addition, the sensor has good stability and reproducibility, and the construction and renewal of the sensor are simple and inexpensive.     

Graphene oxide–MnO_2 nanocomposite-modified glassy carbon electrode as an efficient sensor for H_2O_2

In this study, a new facile preparation method of nanocomposites consisting of graphene oxide and manganese dioxide nanowires(GO/MnO_2 NW_s) was developed. The morphology, structure and composition of the resulted products were characterized by transmission electron microscopy, X-ray diffraction and N_2 adsorption and desorption. The GO/MnO_2 nanocomposite was used as an electrode material for non-enzymatic determination of hydrogen peroxide. The proposed sensor exhibits excellent electrocatalytic performance for the determination of hydrogen peroxide in phosphate buffer solution(PBS, pH7) at an applied potential of 0.75 V. The non-enzymatic biosensor for determination of hydrogen peroxide displayed a wide linear range of 4.90 mmol L~(-1)–4.50 mmol L~(-1)with a correlation coefficient of 0.9992, a low detection limit of 0.48 mmol L~(-1) and a high sensitivity of 191.22μA(mmol L~(-1))~(-1)cm~(-2)(signal/noise, S/N = 3). Moreover, the non-enzymatic biosensor shows an excellent selectivity.     

细胞色素b5-蛋白质相互作用研究

蛋白质-蛋白质相互作用在生命过程中发挥至关重要的作用,特别是血红素类蛋白。细胞色素b5(Cyt b5)是血红素蛋白的一个典型代表,在生物体内通过多种蛋白质-蛋白质相互作用来执行其生物功能。目前所揭示的与Cyt b5相关的蛋白质相互作用包括:细胞色素b5-细胞色素b5还原酶,细胞色素b5-细胞色素P450,细胞色素b5-细胞色素c,细胞色素b5-肌红蛋白或血红蛋白,细胞色素b5-融合蛋白(谷胱甘肽S-转移酶GST和绿色荧光蛋白GFP)和细胞色素b5-转运蛋白(蔗糖转运蛋白SUT1和山梨醇转运蛋白SOT6)等。同一蛋白能与众多不同蛋白相互作用的事实,使我们认识到某些特定蛋白的生物学重要性。另一方面,研究同一蛋白与不同蛋白质间的相互作用将会进一步加深我们对蛋白质结构与功能关系的理解,以及指导新颖蛋白的理性设计与最终应用。     

Gold nanowire assembling architecture for H2O2 electrochemical sensor

Morphological control of nanomaterials is of great interest due to their size and shape-dependent chemical and physical properties and very important applications in many fields such as biomedicine, sensors, electronics and others. In this paper, we reported a simple strategy for synthesizing gold nanowire assembling architecture at room temperature. It is found that two important factors, the proper volume ratio of ethanol to water and poly(vinyl pyrrolidone) (PVP), will play important roles in synthesizing flower-like short gold nanowire assembling spheres. Furthermore, the obtained flower-like gold assembling spheres with high surface-to-volume ratio have been employed as enhancing materials for electrochemical sensing H₂O₂. The present electrochemical sensing platform exhibited good electrocatalytic activity towards the reduction of H₂O₂. The detection limit for H₂O₂ was found to be 1.2 μM, which was lower than certain enzyme-based biosensors.     

Switch-on fluorescence sensor for ascorbic acid detection based on MoS2 quantum dots-MnO2 nanosheets system and its application in fruit samples

In this work,molybdenum disulfide quantum dots(MoS_2 QDs) were firstly prepared by hydrothermal method using sodium molybdate and glutathione as precursors,and applied in ascorbic acid detection.When joining MnO_2 nanosheets into MoS_2 QDs solution,they produced an obvious fluorescence quenching,which should be due to inner filter effect(IFE).Meanwhile,the fluorescent probe was formed,Interestingly,we found that this quenching phenomenon disappeared with the addition of ascorbic acid,In other words,the fluorescence gradually restored.This recovery phenomenon is mainly due to the reduction effect of ascorbic acid for MnO_2 nanosheets.Under the optimum conditions,the limit of detection(LOD) of 39 nmol/L for ascorbic acid was achieved with a linear range of 0.33-5.00 μmol/L.The repeatability was better than 5.0% for ascorbic acid in both standard and fruit samples(n = 3).Moreover,the as-fabricated fluorescent sensing system was successfully employed to detect the ascorbic acid levels in hawthorn and jujube with satisfactory results.     

High performance hybrid supercapacitor based on hierarchical MoS2/Ni3S2 metal chalcogenide

Herein, we synthesized hierarchical MoS₂/Ni₃S₂ structures as electrode materials grown on nickel foam by a facile hydrothermal strategy. The hierarchical MoS₂/Ni₃S₂ structures show high specific capacitance.     

Intermolecular forces for D2, N2, O2, F2 and CO2

The intermolecular potentials for D₂, N₂, O₂, F₂ and CO₂ are determined on the basis of the second virial coeffincients, the polarizabilities parallel and perpendicular to the molecular axes, and the electric quadrupole moment. The repulsive parts of the potentials are taken from the corresponding Kihara core-potentials. Effects of the octopolar induction are taken into consideration in a unique way. The potential depends on relative orientations of the two molecules as well as the distance r between the molecular centers. This dependence is shown in graphs. A measure of the anisotropy of the potential depth is 0.72 for CO₂ 0.36 for D₂, and smaller than 0.27 for N₂ O₂ and F₂. The remarkable anisotropy for CO₂ and D₂ is due to strong electrostatic quadrupole interactions.     

Ba3 (VO4)2-K2 Ba(MoO4)2 and Pb3 (VO4)2-K2 Pb(MoO4)2 systems

Phase equilibria in the Ba₃(VO₄)₂-K₂Ba(MoO₄)₂ and Pb3(VO₄)₂-K₂Pb(MoO₄)₂ systems have been investigated. In the first system, a continuous series of substitutional solid solutions with the palmierite structure is formed, and in the second one, the polymorphic transition in lead orthovanadate at 100°C restricts the extent of the palmierite-type solid solution to 10–100 mol % K₂Pb(MoO₄)₂. Original Russian Text ? V.D. Zhuravlev, Yu.A. Velikodnyi, A.S. Vinogradova-Zhabrova, A.P. Tyutyunnik, V.G. Zubkov, 2008, published in Zhurnal Neorganicheskoi Khimii, 2008, Vol. 53, No. 10, pp. 1746–1748.     

细胞色素b5突变体P40V血红素微环境核磁共振研究

细胞色素b5是一个具有多种重要生理功能的低自旋金属蛋白, 作为呼吸链系统的主要电子传递体之一受到了广泛的重视. 为了研究细胞色素b5表面疏水斑区Pro⁴⁰在细胞色素b5结构与功能上的重要性, 本文利用定点突变技术把细胞色素b5中Pro⁴⁰突变为Val⁴⁰, 并采用1D与2D ¹H NMR的方法对其进行分析, 探讨了Pro⁴⁰突变为Val⁴⁰对细胞色素b5血红素微环境的影响.     

配合物[Cu(H2O)(C12H8N2)2].2ClO4的合成、性质及晶体结构

合成了配合物[Cu(H2O)(C12H8N2)2]*2ClO4(C12H8N2为1,10-邻菲咯啉),用元素分析、摩尔电导、红外光谱及电子光谱进行了表征,并测定了配合物的晶体结构.该晶体属单斜晶系,空间群为CC;晶胞参数a=1.9177(2)nm,b=0.81994(0)nm,c=1.62458(14)nm,β=100.104(6)°;V=2.5419(4)nm3,Z=4,F(000)=1300,DC=1.693g/cm3,R=0.0430,wR=0.1195.中心铜(Ⅱ)离子与两个1,10-邻菲咯啉的四个N原子和一个水分子的氧原子配位,形成了一个变形的三角双锥结构.