Quantum chemical study on the one-carbon unit transfer of imidazolinium

One-carbon unit transfer reaction of folate cofactor model compound, 1-acetyl-2-methyl-imidazolinium, with 1,2-diaminobenzene has been studied theoretically with ONIOM method. The result shows that there are two pathways to complete this reaction because the imidazolinium ring has two breaking patterns. Both the two pathways have six steps. They are combination of two reactants, proton migration, break of five-membered ring, formation of benzimidazole derivate, another proton migration, and formation of final products. In each of the above pathways, the two proton migration steps have higher energy, which illuminate that the reaction is catalyzed by general acid-base. This fact agrees with the experimental results of enzymatic one-carbon unit transfer at oxidation level of formate.     

Use of p-dimethylaminobenzalhyde as a colored reagent for determination of procaine hydrochloride by spectrophotometry

Spectrophotometric determination of procaine hydrochloride is described. The procaine hydrochloride reacts with p-dimethylaminobenzalhyde in glacial acetic acid to form an Schiff base which is a yellow compound, and its maximum absorption wavelength is at 455nm, ₄₅₅=3.46×10⁴. The absorbance for procaine hydrochloride from 0.2 to 15 μg ml⁻¹ obeys Beer's law. The linear regression equation of the calibration graph is C=5.866A−0.02, with a linear regression correlative coefficient is 0.9994 and relative standard deviation (RSD) of 1.7%; the detection limit is 0.1 μg ml⁻¹; recovery is from 92.0 to 110.0%. Effects of reaction medium, temperature, gentamycin, beneylpenicillin, kanamycin, streptomycin, foreign ions, and stand for time on the determination of procaine hydrochloride have been examined. The results obtained by this method agreed with those by the official method (dead-stop titration). This method is rapid and simple, and can be used for the determination of procaine hydrochloride in injection solution of procaine hydrochloride.     

Formation of ring calcium oxalate patterns induced by domains in DPPC Langmuir-Blodgett films

The ring patterns of calcium oxalate crystals were induced by domains in Langmuir-Blodgett （LB） films of dipalmitoylpho- sphatidylcboline （DPPC）. The result was explained by the defects at the ring boundaries of liquid condensed （LC） and liquid expanded （LE） phases of LB film. These boundaries could provide less free energy and much more nucleating sites for COM crystals.     

Practical synthesis of blepharismone,a mating inducing pheromone of Blepharisma japonicum

Both enantiomers of blepharismone, a mating inducing pheromone produced by type II cells of Blepharisma japonicum, were synthesized via the Stille cross-coupling reaction of [4-(tert-butyl-dimethyl-silanyloxy)-2-trimethylstannanyl-phenyl]-carbamic acid tert-butyl ester with an acid chloride derived from (S)- and (R)-malic acid as a key reaction. The mating inducing activity of synthetic (S)-blepharismone was as effective as that of the natural one. The enantiomer (R)-blepharismone showed no mating inducing activity.     

Study of the Fluorescence System of Europium–Enoxacin and its Applications

 This paper is the study of the fluorescence enhancement of Eu³⁺-1-ethyl-6-fluoro-4-oxo-7-(1-piperazinyl)-1,8-naphthyridin-3-carbonic acid (enoxacin, EFLX) system by surfactants. It was found that sodium dodecylbenzenesulfonate (SDBS) exhibits great enhancement on the fluorescence of the Eu-EFLX system. The molar ratio is 1:2:1 for Eu:EFLX: SDBS. Under the optimum conditions, the fluorescence intensity is a linear function of europium in the range of 1.0 × 10⁻⁸ ∼ 5.0 × 10⁻⁶ mol/L, the detection limit is 1.0 × 10⁻⁹ mol/L. The application of the Eu-EFLX-SDBS system for the determination of trace europium in rare earth samples gave satisfactory results. Received October 19, 2000. Revision August 10, 2001.     

氟阴离子在有机合成中的应用：Ⅱ.无水氟化钾催化乙酐与苯甲醛的Perkin反应

用无水醋酸盐催化苯甲醛与乙酐的Perkin反应,一般反应时间较长,产率最高为55—60％.用三乙胺、吡啶和无水碳酸钾等作催化剂,产率也无明显提高.近年来氟阴离子在有机合成中的应用迅速发展,我们曾用无水氟化钾催化成功地实施了丙二酸二乙酯与苯甲醛的Knoevenagel缩合,并研讨了该反应的微环境效应.本工作首次用无水氟     

Investigations on adsorption potentiometry-part VIII. Determination of ultratrace copper in food by derivative adsorption chronopotentiometry

An electroanalytical method, based on derivative chronopotentiometry of the copper complex with 4-[(4-diethylamino-2-hydroxyphenyl) azo]-5-hydroxy-naphthalene-2,7-disulphonic acid (Beryllon III) accumulated on the surface of a hanging mercury drop electrode, for determining trace copper in food has been developed. The dependence of the peak height of reduction of the copper complex on the preconcentration time and preconcentration potential are discussed. Optimum experimental conditions include 0.01 M HOAc, 0.01M NaOAc, 1.0 x 10(-6) Beryllon III and a preconcentration potential of 0.10 V (vs. SCE). Under these conditions the detection limit and the linear range are 4 x 10(-11)M and 6 x 10(-11) -4 x 10(-7)M, respectively. The method was applied to samples of digested rice.     

Ag@Au core/shell triangular nanoplates with dual enzyme-like properties for the colorimetric sensing of glucose

Due to the serious harm of diabetes to human health, development of sensitive assays for glucose level is of high significance for early prevention and treatment of diabetes. Currently, most conventional enzyme-based glucose sensors suffer from high cost and low stability due to the inherent defects of natural enzymes. Herein, we develop a pure nanozyme-based glucose detection method using Ag@Au core/shell triangular nanoplates (TNPs), which combines glucose oxidase (GOD)- and horseradish peroxidase (HRP)-like activities of the Au shell and inherent plasmonic properties of Ag TNPs. The sensing mechanism is based on the fact that the Au shell possessed GOD-like activity, enabling the oxidation of glucose to produce H₂O₂, which can further etch the silver core, leading to the decrease of absorbance at 800 nm and the color change from blue to colorless. Compared with the previous nanozymes-based glucose sensors, our method avoids the use of enzymes and organic chromogenic agent. Moreover, the stability of the Ag@Au core/shell TNPs is much better than that of Ag TNPs due to the protection by the coating of the Au shell. This method was successfully applied to the detection of urine samples from patients with diabetes, indicating its practical applicability for real sample analysis.     

金属铜升温熔化过程的分子动力学模拟

采用分子动力学方法模拟了金属铜的升温熔化过程.原子间作用势采用FS (Finnis-Sinclair)势，结构分析采用双体分布函数(PCF)、均方位移(MSD)等方法.计算结果表明,在连续升温过程中，金属铜在1444 K熔化，在该熔化点的扩散系数为4.31×10－9 m2•s－1.上述结论与实验值相当接近，并且比之采用EAM镶嵌原子势所作模拟得到的结果更佳，说明FS势可以用来处理象液铜这样较复杂的无序体系.本文指出了升温速率在金属熔化过程中所起的作用.     

铬—硫胺素荧光光度法测定铬

荧光法测定铬已有报道,但以氧化还原荧光反应为基础的测定方法尚未见报道。木文研究了铬(Ⅳ)-硫胺素(VB_1)体系,发现在3.5—4.0mol/L的硫酸介质中,铬(Ⅵ)-硫胺素反应生成荧光物质硫胺荧:硫胺素 Cr_2O_7~(2-)?硫胺荧 2Cr~(3 )。硫胺荧的激发波长和发射波长分别为λ_(ex)=405mm,λ_(em)=465nm。可以用来作为Cr(Ⅵ)的荧光定量分析。一般荧光法测定铬的方法虽灵敏度较高,但需有机试剂萃取,手续麻烦。本方法则可直接在水相中进行。