Flow injection analysis methods for determination of diffusion coefficients

Two flow injection analyses (FIA) methods for the determination of diffusion coefficients in a straight single tube FIA system were developed. Based on the analytical solution of the convection-diffusion equation, linear relationships of the logarithmic values of the dispersion coefficient (D) and the half-peak width (W_1/2) with the diffusion coefficient (D_m) were obtained. Experiments were designed to verify these methods. For example, for potassium hexacyanoferrate (III) a D_m value of 0.72 × 10⁵ cm² s⁻¹ was found versus a literature value of 0.76 × 10⁵ cm² s⁻¹ (error, 5%). For potassium hexacyanoferrate (II) a D_m value of 0.67 × 10⁵ cm² s⁻¹ was obtained versus a literature value of 0.63 × 10⁵ cm² s⁻¹ (error, 6%). The diffusion coefficients of some important biomedical compounds, such as dopamine, epinephrine, norepinephrine and ascorbic acid, were then determined. The values of 10⁵ D_m/cm² s⁻¹ are 0.60 ± 0.03, 0.44 ± 0.02, 0.60 ± 0.01 and 0.68 ± 0.06, respectively.     

微量元素铜、锰与精神分裂症

应用等离子体发射光谱法（ＩＣＰ－ＡＥＳ）对精神分裂症急性期男病人４８例，女病人３０例和慢性期男病人５０例，女病人３０例，检测头发中Ｚｎ、Ｆｅ、Ｃｕ、Ｃａ、Ｍｎ５种元素，并与１５８名男女正常人作对照，发现无论是急性期还是慢性期，男女病人的Ｃｕ、Ｍｎ两元素的含量，均显著低于正常人（Ｐ＜０．０５～０．００１）．     

激光解吸电离质谱法分析富勒烯

论述了用激光解吸电离谱法分析富勒烯。因在电离过程中富勒分子不发生裂解，因此这种方法可直接用于富勒烯混合物的分析而勿需任何预分离。还给出了用本法分析较大、较稳定富勒烯分子的质谱图。     

Measurements of HO2 uptake coefficient on aqueous (NH4)2SO4 aerosol using aerosol flow tube with LIF system

The γ(HO₂) was elevated with increase of Cu(II) concentrations in aqueous (NH₄)₂SO₄ aerosol. The threshold of Cu(II) concentration was 10^-3 mol/L for the dramatic increase of γ(HO₂) to 0.1, suggesting sensitive γ(HO₂) value to concentration of transition metal ions in aerosol.     

高效除草剂快杀稗标准物质的制备及表征

从快杀稗工业品出发 ,经活性炭纯化、硅胶柱层析分离制得快杀稗标准物质 ,并进行熔点、高效液相色谱、紫外光谱、元素分析、红外光谱、质谱、核磁共振等方法的表征 ,以高效液相色谱法测得该标准品纯度在99%以上     

Total synthesis and cytotoxicity studies of a cyclic depsipeptide with proposed structure of palau'amide

[structure: see text] Total synthesis of a cyclic depsipeptide with proposed structure of palau'amide is achieved, which features a stereoselective elaboration of its 5,7-dihydroxy-2,6-dimethyldodec-2-en-11-ynoic acid unit. The synthetic compound has potent cytotoxicity against three tumor cell lines but different rotation and NMR data compared to those reported for palau'amide, which implies that its conformation is close to that of palau'amide but that some stereochemistry in palau'amide was misassigned.     

Structural and photocatalytic properties of the new solid photocatalyst In2BiTaO7

In₂BiTaO₇ was synthesized using the solid-state reaction method and its photocatalytic properties were investigated. The results of powder X-ray diffraction (XRD) indicated that the compound crystallizes in the pyrochlore-type structure, cubic system with space group Fd-3m. The lattice parameter is 10.6972(1) ?. In addition, the compound shows strong optical absorption in the visible region (λ > 420 nm) and the band gap of In₂BiTaO₇ was estimated to be about 2.47 eV. For the photocatalytic reaction, H₂ or O₂ evolution was observed from CH₃OH/H₂O or AgNO₃ solution respectively with In₂BiTaO₇ as the photocatalyst under visible light irradiation, indicating that In₂BiTaO₇ is responsive to visible light for splitting water. Furthermore, the catalyst remained photoactive in the wavelength range up to 510 nm. Photocatalytic degradation of methylene blue (MB) dye over the compound was further investigated under visible light irradiation. The results showed that complete removal of aqueous MB could be achieved after irradiation for 135 min over In₂BiTaO₇. Furthermore, under visible light irradiation In₂BiTaO₇ showed markedly higher catalytic activity compared to P-25 for MB photocatalytic degradation.     

Caged Thiophosphotyrosine Peptides

No Abstract     

Kinetic and thermodynamic studies on ligand substitution reactions and base-on/base-off equilibria of cyanoimidazolylcobamide, a vitamin B12 analog with an imidazole axial nucleoside

Ligand substitution reactions of the vitamin B12 analog cyanoimidazolylcobamide, CN(Im)Cbl, with cyanide were studied. Cyanide substitutes imidazole (Im) in the alpha-position more slowly than it substitutes dimethylbenzimidazole in cyanocobalamin (vitamin B12). The kinetics of the displacement of Im by CN- showed saturation behaviour at high cyanide concentration; the limiting rate constant was found to be 0.0264 s(-1) at 25 degrees C and is characterized by the activation parameters: DeltaH(not =) = 111 +/- 2 kJ mol(-1), DeltaS(not =) = +97 +/- 6 J K(-1) mol(-1), and DeltaV(not =) = +9.3 +/- 0.3 cm3 mol(-1). These parameters are interpreted in terms of an I(d) mechanism. The equilibrium constant for the reaction of CN(Im)Cbl with CN- was found to be 861 +/- 75 M(-1), which is significantly less than that obtained for the reaction of cyanocobalamin with CN- (viz. 10(4) M(-1)). pKbase-off for the base-on/base-off equilibrium was determined spectrophotometrically and found to be 0.99 +/- 0.05, which is about 0.9 pH units higher than that obtained previously in the case of cyanocobalamin. In addition, the kinetics of the base-on/base-off reaction was studied using a pH-jump technique and the data obtained revealed evidence for an acid catalyzed reaction path. The results obtained in this study are discussed in reference to those reported previously for cyanocobalamin.