Chemiluminescence from singlet oxygen that was detected at two wavelengths and effects of biomolecules on it

We developed the detection apparatus that equipped with the two-photomultiplier tubes for chemiluminescence from singlet oxygen. Singlet oxygen was generated with reaction between sodium hypochlorite and hydrogen peroxide. The chemiluminescence from singlet oxygen, the dimol light emission (ca. 634 nm) and the monomol light emission (ca. 1270 nm), was observed simultaneously for the same reaction cell. The effects of sodium azide as an antioxidant, human serum albumin, and α-amino acids on the chemiluminescence based on the both emissions were examined; the observed chemiluminescence could provide direct information with regard to the reaction between singlet oxygen and antioxidant/biomolecules. The apparent rate constants for quenching singlet oxygen in the presence of human serum albumin were calculated to be ca. 3.3 × 10⁹ and ca. 8.8 × 10⁸ M⁻¹ s⁻¹ for the dimol and monomol light emissions, respectively, under the present conditions. The chemiluminescence intensities of the dimol emission decreased in the presence of His, Asp, Phe, Ser, and Tyr, and that of the monomol decreased in the presence of Cys and Trp. The chemiluminescence observed in the presence of biomolcules was discussed together with the reactivities of sodium hypochlorite and hydrogen peroxide to biomolecules.     

冠醚和卟啉与花生酸混合单分子膜行为研究

本文将3'-正十五烷基苯并15-冠-5和六种无脂链难于直接成膜的四苯基卟啉与花生酸混合形成单分子膜。结果表明, 冠醚被嵌进而卟啉被挤出花生酸单分子层。卟啉-花生镉LB膜的可见吸收光谱指出卟啉分子成团聚集。扫描电镜观察了卟啉-花生酸镉混合LB膜的表面形貌, 在膜表面上无金涂层时直接测到了混合膜的相分离。     

Enthalpy changes upon dilution and ionization of poly(L-glutamic acid) in aqueous solutions

The enthalpy changes accompanying the dilution and ionization of poly(L-glutamic acid) in water have been measured at 25 degrees C for two degrees of polymerization (DP = 115 and DP = 480) at various degrees of ionization, alpha, for a concentration range from about 0.2 to 0.002 monomol/L. The heat of dilution displays an unusual dependence on the degree of ionization, which is in sharp contrast to the behavior of other weak carboxylic polyelectrolytes, such as poly(acrylic acid). The exothermic heat effects observed at low values of alpha become endothermic for the region where the helix-coil transition is most pronounced, and for high degrees of ionization, they are exothermic again. Evidently, an endothermic heat effect, produced by an additional conformational transition in the dilution process, is superimposed on the exothermic enthalpy of dilution, and it overweighs the latter in the region of alpha where the conformational transition is prevailing. The calorimetric titration curve, which gives the dependence of the heat of ionization, deltaH(i), on alpha, has a maximum and is typical for poly(carboxylic acids) which undergo pH-induced conformational transition, such as poly(methacrylic acid). The values of deltaH(i) obtained at two polymer concentrations indicate that the enthalpy of ionization depends on the polypeptide concentration.     

Generation of Singlet Molecular Oxygen by Lipid Hydroperoxides and Nitronium Ion†

Singlet molecular oxygen is a reactive species involved in biological oxidative processes. The major cellular targets of singlet molecular oxygen are unsaturated fatty acids in the membrane, as well as nucleic acids and proteins. The aim of this study was to investigate whether lipids and commercial hydroperoxides generate singlet molecular oxygen, in presence of nitronium and activated nitronium ion. For this purpose, monomol light emitted in the near-infrared region (λ = 1270 nm) was used to monitor singlet molecular oxygen decay in different solvents, with different hydroperoxides and in the presence of azide. Direct measurements of the singlet molecular oxygen spectrum at 1270 nm recorded during the reaction between lipids and commercial hydroperoxides and nitronium ions unequivocally demonstrated the formation of this excited species.     

Self-assembled polyelectrolyte multilayered films on Nafion with lowered methanol cross-over for DMFC applications

The paper is concerned with the deposition of self-assembled polyelectrolyte multilayer on Nafion membrane by layer-by-layer (LbL) technique with lowered methanol cross-over for direct methanol fuel cell (DMFC) applications. The formation of self-assembled multilayered film on Nafion was characterized by UV–vis spectroscopy and it was found that the polyelectrolyte layers growth on the Nafion surface regularly. Furthermore, the proton conductivity and methanol cross-over measurements were carried out for characterization of the LbL self-assembled composite membranes. The results showed that the concentration and pH of the polyelectrolytes significantly affect the proton conductivity and methanol barrier properties of the composite membranes. 10⁻¹ monomol polyelectrolyte concentration and pH 1.8 was found to be optimum deposition conditions considering proton conductivity and methanol permeation properties of the LbL self-assembled composite membranes. The methanol permeability of the 10 bi-layers of PAH1.8/PSS1.8 deposited LbL self-assembly composite membrane was significantly suppressed and found to be 4.41 × 10⁻⁷ cm²/s while the proton conductivity value is in acceptable range for fuel cell applications.     

Triplet Excited States and Singlet Oxygen Production by Analogs of Red Wine Pyranoanthocyanins

During the maturation of red wines, the anthocyanins of grapes are transformed into pyranoanthocyanins, which possess a pyranoflavylium cation as their basic chromophore. Photophysical properties of the singlet and triplet excited states of a series of synthetic pyranoflavylium cations were determined at room temperature in acetonitrile solution acidified with 0.10 mol dm^?3 trifluoroacetic acid (TFA, to inhibit competitive excited state proton transfer) and at 77 K in a rigid TFA‐acidified isopropanol glass. In solution, the triplet states of these pyranoflavylium cations are efficiently quenched by molecular oxygen, resulting in sensitized formation of singlet oxygen, as confirmed by direct detection of the triplet‐state decay by laser flash photolysis and of singlet oxygen monomol emission in the near infrared. The strong visible light absorption, the relatively small singlet‐triplet energy differences, the excited state redox potentials and the reasonably long lifetimes of pyranoflavylium triplet states in the absence of molecular oxygen suggest that they might be useful as triplet sensitizers and/or as cationic redox initiators in polar aprotic solvents like acetonitrile.     

A new quasiclassical method for modeling the high-resolution spectra of polyatomic systems

A new quasiclassical method for quantum autocorrelation functions based on the semiclassical limit in Wigner phase space has been derived. Unlike the existing quasiclassical method, the new method enables long-time simulations, thus making it possible to locate quantum spectral lines very precisely. The new method has been tested for a one-dimensional anharmonic oscillator fitted to the H(2) molecule and for a six-dimensional calculation of the Ar(2)I van der Waals cluster in adiabatic approximation. The obtained results compare well with the benchmark quantum-mechanical calculations and are also roughly comparable to the experimental Ar(2)I(-) zero-kinetic-energy photoelectron spectrum, which is available in the literature.     

Rapid determination of banned Sudan I in foodstuffs using a mesoporous SiO2 modified electrode

Rapid determination of Sudan I in foodstuffs is very important because it was found to be a carcinogen and its use in the food industry was banned. A rapid, sensitive, and convenient electrochemical method was developed for the determination of Sudan I based on the distinctive properties of mesoporous SiO2. The electrochemical responses of Sudan I were investigated. A sensitive oxidation peak was observed for Sudan I, and the peak currents greatly increased at the mesoporous SiO2-modified electrode, which can be attributed to its large surface area and high accumulation efficiency. The effects of pH, amount of mesoporous SiO2, scan rate, accumulation potential, and time were examined on the oxidation signals of Sudan I. The linear range was from 4.00 x 10(-8) to 2.00 x 10(-5) M, and the LOD was 7.50 x 10(-9) M. The newly developed method was successfully used to detect and quantify Sudan I in hot chili powder and juice samples.     

一种计算Feshbach共振态寿命的新方法

在自然碰撞坐标下构建偏分势能面, 利用数值传播方法求解沿反应坐标的核运动方程, 然后用过渡态波函数的相移因子构造反应体系共振态寿命矩阵. 这是一种直接计算化学反应散射共振寿命的量子散射方法. 用此方法计算了I+HI(υ)→IH(υ’)+I体系的第一散射共振态寿命, 所得数值与Neumark 的高分辨阈值光分离光谱实验的结果相一致.     

Electrical conductivity of some cationic polysaccharides. I. Effects of polyelectrolyte concentration,charge density,substituent at the ionic group,and solvent polarity

Electrolytic conductivity behavior of some cationic polysaccharides in water, methanol, and the mixtures water/methanol is presented. The polyelectrolytes investigated contain quaternary ammonium salt groups, N‐alkyl‐N,N‐dimethyl‐2‐hydroxypropyleneammonium chloride, attached to a dextran backbone. This study considers the influences of polymer concentration (1 × 10^?6 < C < 1 × 10^?2 monomol L^?1) and the charge density (ξ = 0.48–3.17) modified either by changing charge distance (b) or dielectric constant of the solvent (ε) on polyion–counterion interaction in salt‐free solutions. Above the critical value, ξ_c = 1, the variation of the equivalent conductivity (Λ) as a function of concentration is typical for a polyelectrolyte behavior. The conductometric data in water were analyzed in terms of the Manning's counterion condensation theory. The presence of longer alkyl chains at quaternary N atoms was found to have a negligible influence on the Λ values. The results show that the decrease of the medium polarity results in the decrease of the number of free ions and, consequently, of the equivalent conductivity values. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3584–3590, 2005     

Aggregation of quaternary ammonium gemini surfactants C12-s-C12.2Br in n-heptane/n-hexanol solution: effect of the spacer chains on the critical reverse micelle concentrations

The critical reverse micelle concentrations of C(12)-s-C(12).2Br (s=2,3,4,5,6,8,12) in n-heptane/n-hexanol solutions, cmc(I)s, have been determined by absorption spectrum method using iodine as probe. The values of cmc(I)s are smaller than those of the critical micelle concentrations (cmc(aq)s) in aqueous solution and reach a maximum at s=4, which is similar to the variation of cmc(aq) with s. The variation of cmc(I) with s is attributed to the alteration in the spacer chain conformation, i.e. when the spacer is short enough, it may adopt stretch configuration and when the spacer is long, it tends to bend towards the continuous oil phase to achieve a more densely packing of the quaternary ammonium heads on the surface of the core.     

A modified method of separating Tl(I) and Tl(III) in aqueous samples using solid phase extraction

In spite of the development of new measurement techniques in recent years, the rapid and accurate speciation of thallium in environmental aqueous samples remains a challenge. In this context, a novel method of solid phase extraction (SPE), involving the anion exchange resin AG1-X8, is proposed to separate Tl(I) and Tl(III). In the presence of diethylene triamine pentacetate acid (DTPA), Tl(III) and Tl(I) can be separated by selective adsorption of Tl(III)-DTPA onto the resin, Tl(III) is then eluted by a solution of HCl with SO₂. The validity of this method was confirmed by assays of standard solutions of Tl(I) and Tl(III). The proposed method is shown to have an outstanding performance even in solutions with a high ratio of Tl(I)/Tl(III), and can be applied to aqueous samples with a high concentration of other electrolytes, which could interfere with the measurement. Portable equipment and reagents make it possible to use the proposed method routinely in the field.     

Au(I)炔基配合物激发态性质的理论研究

用MP2方法和CIS方法分别优化了Au(I)炔基配合物及相应炔烃的基态和激发态的结构. 计算结果表明, 在基态, 分子有向中间收缩的趋势, Au(I)的修饰作用减弱了配体内部原子间的成键作用. 随着分子链长增长, Au(I)与配体间的相互作用减弱; 激发态的电子跃迁减弱了, Au(I)与配体间的相互作用, 并且这种影响随着分子链增长而更加明显. 计算得出Au(I)炔基配合物体系的荧光发射光谱并发现其独特的发光性质, 说明取代H原子的—AuPH3比—H更具有离子性.     

卟啉化合物碳同位素的气相色谱同位素比值质谱测定技术

 对于卟啉碳同位素的测定 ,传统方法 (用HPLC分离出单个卟啉化合物 ,然后燃烧成CO2 进行碳同位素的测定 )需要的样品量大 (几mg)、耗时长 ,限制了其在化学、地球科学中的应用。该文作者建立的方法是通过对卟啉化合物进行衍生化反应 ,以增强卟啉的挥发性 ,使其适用于气相色谱 同位素比值质谱 (GC IRMS)技术。对衍生化反应的整个过程进行了同位素测定 ,证实最终的衍生化硅卟啉与初始的自由基卟啉化合物碳同位素的差值在分析误差范围之内 ,无明显的同位素分馏。     

A quick, convenient and economical method for the reliable determination of methylglyoxal in millimolar concentrations: the N-acetyl-l-cysteine assay

The determination of methylglyoxal (MG) concentrations in vivo is gaining increasing importance as high levels of MG are linked to various health impairments including complications of diabetes. In order to standardize the measurements of MG in body fluids, it is necessary to precisely determine the concentration of MG stock solutions used as analytical standards. The "gold standard" method for the determination of MG concentration in the millimolar range is an enzyme-catalyzed endpoint assay based on the glyoxalase I catalyzed formation of S-lactoylglutathione. However, as this assay used purified glyoxalase I enzyme, it is quite expensive. Another method uses a derivation reaction with 2,4-dinitrophenylhydrazine, but this substance is explosive and needs special handling and storage. In addition, precipitation of the product methylglyoxal-bis-2,4-dinitrophenylhydrozone during the reaction limits the reliability of this method. In this study, we have evaluated a new method of MG determination based on the previously published fast reaction between MG and N-acetyl-L-cysteine at room temperature which yields an easily detectable condensation product, N-α-acetyl-S-(1-hydroxy-2-oxo-prop-1-yl)cysteine. When comparing these three different assays for the measurement of MG concentrations, we find that the N-acetyl-L-cysteine assay is the most favorable, providing an economical and robust assay without the need for the use of hazardous or expensive reagents.     

Comparison of two methods for the extraction of fat from human milk

We compared two methods for the extraction of fat from human milk. Pure fat extraction techniques are necessary for qualitative and quantitative analysis of milk fat, of which triglycerides account for more than 98%. Method I was a conventional liquid-liquid system for the fat extraction while method II was a faster approach using a haematocrit technique. No significant differences were observed between both methods neither in the fat content determined gravimetrically, nor in qualitative and quantitative analysis of triglycerides by high-performance liquid chromatography (HPLC) with evaporative light-scattering detection (ELSD). We conclude that method II offers substantial advantages over the conventional method (method I). The former requires less reagents and material and is simpler and less time-consuming (approximately 30 min instead of 90 min). Therefore, a new method will make it possible to extract fat of more human milk in the same time.     

稳态荧光探针法研究Ca2+与十二烷基苯磺酸钠的相互作用

用稳态荧光探针法研究了Ca2+与十二烷基苯磺酸钠(SDBS)的相互作用.研究发现,Ca2+与SDBS在一定条件下产生沉淀.将芘探针溶在有沉淀体系中所测得的第一峰荧光强度I1与第三峰荧光强度I3之比(I1/I3)的大小随表面活性剂浓度变化的突变点与用透光率法测得的沉淀点相对应;将沉淀体系离心,把芘溶在离心后所得的上清液中,此时所测得的I1/I3值随表面活性剂浓度变化的突变点则与透光率法测得的沉淀开始溶解的点相对应.且随着盐的加入及盐浓度的增加,芘的I1/I3值减小.在相同盐浓度下,二价金属盐比一价金属盐对芘的I1/I3值影响大.     

Adsorption and radiochemical separation of caesium(I) using zirconium phosphate ion exchanger

A rapid and selective method has been developed for the separation of caesium(I) from other metal ions by adsorbing it on zirconium phosphate ion exchanger. Various parameters involved in the quantitative adsorption of caesium(I) on the ion exchanger have been evaluated employing¹³⁷Cs as a tracer.     

A simple and efficient synthesis of 3-cyano-4-phenyl-2-pyridone

A preparatively useful method for the synthesis of 3-cyano-4-phenyl-2-pyridone (I) is described. Reaction of 2-cyano-3-methylcinnamamide (VII) with N,N-dimethylformamide dimethyl acetal affords the corresponding dimethylaminomethylidene amide VIII which in turn, is thermally cyclized to I in DMF solvent. The advantages of this method include mild reaction conditions for short periods to give good yields of I on large scales without chromatographic purification.     

Kinetic-spectrophotometric determination of trace amounts of silver using the oxidation of thionine with peroxodisulfate.

A simple, rapid and sensitive method has been developed for determination of traces of silver(I) (0.2 - 13 ng mL(-1)) based on its catalytic effect on the oxidation of thionine by peroxodisulfate in the presence of 1 - 10 phenanthroline as an activator. The reaction is monitored spectrophotometrically by measuring the decrease in absorbance of thionine at 600 nm by the fixed time method. The detection limit is 0.098 ng mL(-1) and the relative standard deviation for 0.5, 3.0, 5.0 and 10 ng ml(-1) Ag(I) are 4.1, 1.37, 1.06 and 0.64%, respectively. The method is free from most interferences and it was applied to determination of silver in photographic solutions and well-water samples.