Chemical characteristic of bioactive polysaccharides isolated from Ornithogalum caudatum Ait.

A water-soluble crude extract prepared from Ornithogalum caudatum Ait. (OCA) showing a high immunomodulating activitiy was isolated and characterized by virtue of get filtration and column chromatography. The presence of the monosaccharides has been established by the chemical analysis. The quantitative analysis of the alditol acetate derivatives of them showed the ratios of the monosaccharides analyzed by means of GC respectively. The concentrations of protein(280 nm) and carbohydrate (496 nm) were detected respectively. The information of the molecular weight from the pure polysaccharide was obtained by several standard Dextrans from the Sephadex chromatography.

Electrocatalytic oxidation of dopamine at a cobalt hexacyanoferrate modified glassy carbon electrode prepared by a new method

A stable electroactive thin film of cobalt hexacyanoferrate (CoHCF) was electrochemically deposited on the surface of a glassy carbon (GC) electrode with a new and simple method. The cyclic voltammograms of the CoHCF Film modified GC (CoHCF/GC) electrode prepared by this method exhibit two pairs of well-defined redox peaks, at scan rates up to 200 mV s(-1). The advantage of this method is that it is easy to manipulate and to control the surface coverage of CoHCF on the electrode surface. The modified electrode shows good electrocatalytic activity towards the electrochemical reaction of dopamine (DA) in a 0.1 mol dm (3) KNO3 + phosphate buffer solution (pH 7.0). The rate constant of the electrocatalytic oxidation of DA at the CoHCF/GC electrode is determined by employing rotating disk electrode measurements.

Promoter effect of La3+ on the electrochemical reaction of microperoxidase-11

The effect of La3+ on the electrochemical behavior and structure of heme undecapeptide-microperoxidase-11 (MP-11)-in the aqueous solution was investigated using cyclic voltammetry, circular dichroism (CD) and UV-vis absorption spectrometry. It was found for the first time that La3+ would promote the electrochemical reaction of MP-11 at the glassy carbon (GC) electrode. This is mainly due to the fact that La3+ would induce more beta-turn and alpha-helical conformations from the random coil conformation of MP-11 and increase the non-planarity of the heme.

Conformation change of horseradish peroxidase in lipid membrane

The electrochemical behavior of horseradish peroxidase (HRP) in the dimyristoyl phosphatidylcholine (DMPC) bilayer on the glassy carbon (GC) electrode was studied by cyclic voltammetry. The direct electron transfer of HRP was observed in the DMPC bilayer. Only a small cathodic peak was observed for HRP on the bare GC electrode. The electron transfer of HRP in the DMPC membrane is facilitated by DMPC membrane. UV-Vis and circular dichroism (CD) spectroscopy were used to study the interaction between HRP and DMPC membrane. On binding to the DMPC membrane the secondary structure of HRP remains unchanged while there is a substantial change in the conformation of the heme active site. Tapping mode atomic force microscopy (AFM) was first applied for the investigation on the structure of HRP adsorbed on supported phospholipid bilayer on the mica and on the bare mica. HRP molecules adsorb and aggregate on the mica without DMPC bilayer. The aggregation indicates an attractive interaction among the adsorbed molecules. The molecules are randomly distributed in the DMPC bilayer. The adsorption of HRP in the DMPC bilayer changes drastically the domains and defects in the DMPC bilayer due to a strong interaction between HRP and DMPC films.

Electrochemical study of ion channel behavior in incorporated poly L-glutamate bilayer lipid membranes

The lipid layer membranes were fabricated on the glassy carbon electrode (GC) and demonstrated to be bilayer lipid membranes by impedance spectroscopy. The formation of incorporated poly L-glutamate bilayer lipid membrane was achieved. The ion channel behavior of the incorporated poly L-glutamate membrane was determined. When the stimulus calcium cations were added into the electrolyte, the ion channel was opened immediately and exhibited distinct channel current. Otherwise, the ion channel was closed. The cyclic voltammogram at the GC electrode coated with incorporated poly L-glutamate DMPC film response to calcium ion is very fast compared with that at the GC electrode coated only with DMPC film. Ion channel current is not dependent on the time but on the concentration of calcium. The mechanism of the ion channel formation was investigated.

Electrocatalytic oxidation of dopamine by ferrocene in lipid film cast on a glassy carbon electrode

The ferrocene-lipid film electrode was successfully prepared by means of casting the solution of ferrocene and lipid in chloroform onto a glassy carbon (GC) electrode surface. Ferrocene saved in the biological membrane gave a couple of quasi-reversible peaks of cyclic voltammogram. The electrode displays a preferential electrocatalytic oxidation of dopamine (DA). The effect of electroccatalytic oxidation of DA depends on the solution pH and the negative charge lipid is in favor of catalytic oxidation of DA. The characteristic was employed for separating the electrochemical responses of DA and ascorbic acid (AA). The electrode was assessed for the voltammetric differentiation of DA and AA. The measurement of DA can be achieved with differential pulse voltammetry in the, presence of high concentration of AA. The catalytic peak current was proportional to the concentration of DA in the range of 1 x 10(-4)-3 x 10(-3) mol/L.

气相色谱-质谱中定量分析技术的应用

本文对气相色谱 -质谱 (GC- MS)定量分析技术及其在我国的应用进行了综述 ,较详细地阐述了峰匹配、质量色谱和选择离子检测 3种定量分析方法与应用 ,共引用文献 39篇

Ion channel behavior of supported bilayer lipid membranes on a glassy carbon electrode

A new kind of solid substrate, a glassy carbon (GC) electrode, was selected to support lipid layer membranes. On the surface of the GC electrode, we made layers of didodecyldimethylammonium bromide (a synthetic lipid). From electrochemical impedance experiments, we demonstrated that the lipid layers on the GC electrode were bilayer lipid membranes. We studied the ion channel behavior of the supported bilayer lipid membrane. In the presence of perchlorate anions as the stimulus and ruthenium(II) complex cations as the marker ions, the lipid membrane channel was open and exhibited distinct channel current. The channel was in a closed state in the absence of perchlorate anions.

Study on adsorption and oxidation of calf thymus DNA at glassy carbon electrode

The oxidation and adsorption of the temperature-denatured DNA at GC electrode are studied by differential pulse voltammetry and in situ FTIR spectroelectrochemistry. The temperature-denatured DNA is adsorbed and formed a DNA multilayer at electrode surface. The temperature-denatured DNA showing partly reversible process was first observed based on the reduction peaks appearing at negative scans and the reversible spectral change. The oxidation product of the temperature-denatured DNA can not diffuse away from the electrode surface easily due to the impediment of the DNA multilayer, so it can be partly reduced.

Electrocatalytic oxidation of NADH by rutin in biomembrane-like films on glassy carbon electrode

Stable lipid film was made by casting dipalmitoylphosphatidylcholine (DPPC) and rutin onto the surface of a glassy carbon (GC) electrode. The electrochemical behavior of rutin in the DPPC film was studied. The modified electrode coated with rutin gave quasi-reversible reduction-oxidation peak on cyclic voltammogram in the phosphate buffer (pH 7.4). The peak current did not decrease apparently after stored at 4 degreesC for 8 hours in refrigerator. This model of biological membrane was used to investigate the oxidation of dihydronicotinamide adenine dinucleotide (NADH) by rutin. Rutin in the film acts as a mediator. The modified electrode shows a great enhancement and the anodic peak potential was reduced by about 220 mV in the oxidation of 5 X 10(-3) mol L-1 NADN compared with that obtained at a bare glassy carbon electrode. (C) 2000 Elsevier Science S.A. All rights reserved.

Study on a novel polyimide precursor prepared by a modified polymerization of monomeric reactants (MPMR) procedure

A novel polyimide precursor based on the dimethyl ester of 3,3',4,4'-biphenyltetracarboxylic acid, 4,4'-methylene dianiline and the monomethyl ester of 5-norbornene-2,3-dicarboxylic acid (BPDE/MDA/NE) was prepared by a modified polymerization of monomeric reactants (PMR) approach (MPMR). The composition of the precursor was quantitatively characterized by means of FTIR, HPLC and GC. The fractions of imide, amic ester and amic acid units in the precursor, typically prepared by refluxing in 1,4-dioxane for 2 h, were 33.7, 30.8 and 1.1 mol-%, respectively. The portion of free MDA was 3.34 wt.-% as determined by HPLC.

微过氧化物酶-11修饰电极对O_2和H_2O_2的电催化还原

运用电化学循环伏安法和旋转圆盘电极技术研究了O2 和H2O2 在Nafion膜固定的微过氧化物酶 11修饰的玻碳 (MP 11 +Nafion/GC)电极上的电化学还原.结果表明,修饰电极对O2 和H2O2 的还原均具有电催化作用.测定和比较了O2 和H2O2 在MP 11 +Nafion/GC电极上电催化还原反应的一些动力学参数.发现O2 在修饰电极上经历了四电子还原 ,且还原过程与溶液的 pH值有关.

西洋参多糖PPQI-1～4的分离和表征

为研究生物活性西洋参多糖的性质 ,采取热水提取乙醇分级沉淀、葡聚糖凝胶分离等手段从西洋参根中分得 4个纯多糖 (PPQI- 1～ 4)。基质辅助激光解吸电离质谱 (MAL DI- MS)测定分子量 ,乙酰化衍生结合GC分析测定糖组成。甲基化结合 GC- MS分析测定糖苷键连接位点。结果表明 ,这 4个多糖化合物都是杂多糖 ,分别由不同比例的阿拉伯糖、半乳糖、葡萄糖、糖醛酸组成 ,糖醛酸含量为 30 %～ 6 0 % ,分子量范围 2～ 7万

Oxidation of ascorbic acid by rutin at a glassy carbon electrode modified with lipid films

A stable film was prepared by casting dipalmitoylphosphatidylcholine (DPPC) and rutin onto the surface of a glassy carbon (GC) electrode. The electrochemistry behavior of rutin in the DPPC film was investigated. The modified electrode coated with rutin shows a quasi-reversible reduction-oxidation peak on the cyclic voltammogram in phosphate buffer (pH 7.4). This model of biological membrane was not only used to provide biological environment but also to investigate the oxidation of ascorbic acid by rutin. The DPPC-rutin modified electrode behaves as electrocatalytic oxidation to ascorbic acid. The oxidation peak current of ascorbic acid increases drastically and the peak potential of 4 x 10(-4) mol L-1 ascorbic acid shifts negatively about 100 mV compared with that obtained at a bare glassy carbon electrode. The catalytic current increased linearly with the ascorbic acid concentration in the range of 2 x 10(-4) mol L-1 and 1.4 x 10(-3) mol L-1 at a scan rate of 50 mV s(-1).

Ion-channel sensing of ferricyanide anion based on a supported bilayer lipid membrane

Ferricyanide anion has usually been used as a marker of ion-channel sensors. In this work we first found that ferricyanide, itself, can act as a stimulus to regulate the permeability of sBLM prepared from didodecyldimethylammonium bromide (a kind of synthetic lipid) on a GC electrode. We used cyclic voltammetry and a.c. impedance to investigate this phenomenon. The interaction between sBLM and ferricyanide concerns time. Furthermore, we developed a sensor for ferricyanide anion. The ion-channel sensor is highly sensitive. It can detect ferricyanide concentration as low as 5 muM.