稀土对3’,5’-环腺嘌呤单核苷酸与3’,5’-环鸟嘌呤单核苷酸的快速断裂作用

在温和条件下能快速切断核酸的人工酶有许多重要的潜在应用价值,如作为模拟的限制性内切酶并发展到新的抗癌药物,因此,长期以来人们致力于研究具有高效率及高选择性的人工酶.关于稀土对核酸断裂作用的研究尚不多,而稀土对环核苷酸的催化水解作用只有Sumaoka等曾报道Ce~(3+)对3’,5’-环腺嘌呤单核苷酸(cAMP)有快速的水解作用,稀土对不同环核苷酸的催化水解作用尚未见报道.3’,5’-环腺嘌呤单核苷酸与3’,5’-环鸟嘌呤单核苷酸(cGMP)具有调节细胞应答及细胞间信息传递的作用,且细胞内不同环核苷酸的变化与某些心血管疾病的发病机理有关.本文用高压液相色谱(HPLC)和核磁共振(NMR)研究了稀土对cAMP与cGMP的断裂作用,并深入探索了其机理,这对于寻找高效率及高选择性的核酸催化体系,阐明稀土在生物体内的作用具有重要的意义.

Preparation of 1,3,5-thiadiazine-2-thione derivatives of chitosan and their potential antioxidant activity in vitro

Three new kinds of 1,3,5-thiadiazine-2-thi one derivatives of chitosan with two different molecular weight (SATTCS1, SATTCS2, TITTCS1, TITTCS2, CITTCS1 and CITTCS2) have been prepared. Their structures were characterized by IR spectroscopy. The substitution degree of derivatives calculated by elemental analyses was 0.47, 0.42, 0.41, 0.38, 0.41 and 0.36, respectively. The result shows that substitution degree of derivatives was higher with lower molecular weight. The antioxidant activity was studied using an established system, such as bydroxyl radical scavenging, superoxide radical scavenging and reducing power. Antioxidant activity of the 1,3,5-thiadiazine-2-thione derivatives of chitosan were stronger than that of chitosans and antioxiclant activity of low molecular weight derivatives were stronger than that of high molecular weight derivatives. It is a potential antioxidant in vitro. (c) 2007 Elsevier Ltd. All rights reserved.

Electrochemical impedance spectroscopy analysis for oxygen reduction reaction in 3.5% NaCl solution

The electrochemical impedance spectroscopy (EIS) at different potentials has been used to study the oxygen reduction reaction (ORR) in 3.5% NaCl solution on glassy carbon (GC) electrode in this work. Results show that ORR consists of three two-electron reaction steps and both superoxide ion (O-2(-)) and hydrogen peroxide (H2O2), which are produced by ORR, obstruct the diffusion of oxygen to the surface of the electrode and make the EIS results change into a transmissive finite diffusion process with the real part contraction and a reflective finite diffusion process from a semi-infinite diffusion process. The values of electron transfer resistance (R-t) and diffusion resistance (R-d) were calculated from EIS. O-2(-) influenced strongly on the Rt values and induced a maximum at -0.45 V.

Inhibition Effect of 2,3,5-Triphenyl-2H-tetrazolium Chloride and 2,4,6-Tri(2-pyridyl)-s-triazine on the Corrosion of Mild Steel in 1 mol/L HCl and Mechanism Study (II)

The inhibitory effect of 2,3,5-triphenyl-2H-tetrazolium chloride (TTC) and 2,4,6-tri(2-pyridyl)-s-triazine (TPT) molecules on the corrosion of mild steel in 1 mol/L HCl and microcosmic inhibitory mechanism were investigated by X-ray photoelectron spectroscopy and ellipsometry. XPS results showed that C Is and N Is peaks of TTC, C Is and N Is peaks of TPT and their integral areas were obtained, which suggested the layer of the inhibitors (TTC or TPT) should have effectively protected the mild steel surface from the corrosion; and the depression from the inhibitors for the corrosion of mild steel surface was studied using ellipsometry combined with potentiodynamic polarization and the phasic difference was gained, which displayed the inhibitory coverage of the inhibitors formed.

2,3,5-triphenyl-2H-tetrazolium chloride and 2,4,6-tri(2-pyridyl)-s-triazine on the corrosion of mild steel in HCl

Electrochemical measurement, quantum chemical method, and scanning electron microscopy (SEM) were performed to investigate the inhibitive effect of 2,3,5-triphenyl-2H-tetrazolium chloride (TTC) and 2,4,6-tri(2-pyridyl)-s-triazine(TPT) on the corrosion of mild steel in 1mol.L-1 HCl at room temperature. Impedance spectroscopy measurement showed that the polarization resistance increased and that double layer capacitance decreased with the increase in the inhibitive concentration, and the results of potentiodynamic polarization showed that the inhibitors suppressed both cathodic and anodic processes of steel corrosion without change in the mechanism. Higher the orbital density distribution strength of the lowest unoccupied molecular orbital, higher is the molecule dipole, and lower energy gap between the energy of the highest occupied molecular orbital and the energy of the lowest unoccupied molecular orbital resulted in higher inhibitory efficiency. The results of SEM analysis showed that the metal was protected from aggressive corrosion by the addition of TTC and TPT.

Catena-Poly[[[tetra-mu(2)-aqua-heptaaqua-(mu(2)-benzene-1,3,5-tricarboxylato)-mu(3)-hydroxido-trinickel(II)sodium]-mu(4)-benzene-1,3,5-tricarboxylato]sesqui-hydrate]

The title coordination polymer, {[Ni3Na(OH)(C9H3O6)(2)( H2O)(11)] center dot 1.5H(2)O}(n), is built up from three independent Ni-II ions and one Na-I cation bridged by benzene-2,4,6-tricarboxylate ( BTC) ligands and water molecules. Three Ni-II ions are bridged by three bidentate carboxylate groups of three BTC ligands, two aqua ligands and one OH- unit, to form a trinuclear metal cluster. The Na-I cation is bonded to the Ni-II cluster by two bridging water molecules. One of the three BTC ligands bridges neighbouring clusters into one-dimensional chains, which are further connected through a complex hydrogen-bonding scheme, forming a three-dimensional suprastructure. The title complex is isomorphous with the previously reported Co-II complex.

Bis(2,3,5-triphenyltetrazolium) tetrachloridocadmate(II)

The title compound, ( C19H15N4)(2)[ CdCl4], a salt comprising two 2,3,5-triphenyl-substituted tetrazolium cations and a tetrachloridocadmate(II) anion, was synthesized by hydrothermal methods. In the anion, the Cd-II ion is tetrahedrally coordinated by four chloride anions. In the crystal structure, four cations and two anions pack into inversion-related subunits linked by C-H center dot center dot center dot Cl and offset pi-stacking interactions.Each of these subunits is surrounded by six others. Intermolecular pi-pi stacking interactions between phenyl rings are observed along the a axis, with perpendicular distances between the ring planes of 3.6015 and 3.6934 angstrom.

1-（2-萘基）-3-甲基-5-吡唑啉酮衍生试剂的制备及其在高效液相色谱-质谱法测定糖类化合物中的应用

以1-（2-萘基）-3-甲基-5-吡唑啉酮（NMP）作为柱前衍生试剂,建立了简单、灵敏的糖类组分的反相高效液相色谱测定方法。NMP与糖在氨为催化剂的条件下,于70℃下反应可获得稳定的衍生产物。在HypersilODS2反相色谱柱上,实现了8种单糖的基线分离。衍生物线性相关系数均大于0.9985,检出限为0.58-1.1pmol。利用柱后在线串联质谱的电喷雾电离正离子模式监测,获得了各组分的质谱定性及裂解规律,特别是m/z473的特征碎片离子可作为单糖NMP衍生物的判定依据。与1-苯基-3-甲基-5-吡唑啉酮（PMP）相比,NMP对糖的衍生化具有灵敏、简单、质谱裂解规律性强、重现性好等优点。该方法用于测定油菜花粉多糖中的单糖组成,结果令人满意。

1，3，5-三氯苯在土壤沉积物水体系中的吸附过程研究

以自然土壤、沉积物样品为研究对象，研究了1，3，5-三氯苯在样品上的等温吸附过程。结果表明，线性模型和Freundlich模型能较好地拟合所有样品的等温线，而双区位反应模型(DRDM)适用范围有限。研究表明，三氯苯的吸附容量大小主要取决于样品中有机碳的含量，并且与不可提取态有机质和粘土矿物含量有一定的关系。以自然土壤、沉积物样品为研究对象，研究了1，3，5-三氯苯在样品上的等温吸附过程。结果表明，线性模型和Freundlich模型能较好地拟合所有样品的等温线，而双区位反应模型(DRDM)适用范围有限。研究表明，三氯苯的吸附容量大小主要取决于样品中有机碳的含量，并且与不可提取态有机质和粘土矿物含量有一定的关系。

3-5岁幼儿认知灵活性的发展

To test preschoolers’ development of cognitive flexibility--an ability to solve a problem in one way and to then switch solution strategies, and the mechanism involved in the development, 3-5-year-olds are asked to perform switching tasks in which the experimenter manipulates the way the stimuli are presented: consecutive or simultaneous; the way the switching happens: between dimensions or within a dimension; the conceptual domains involved: shape, color, number and direction; the specific labels used. The main results of this work are presented below: (1) 3-5-year-olds’ cognitive flexibility develops with age, yet its development is not of the same speed in extra-dimensional switch tasks and inter-dimensional reversal tasks. 3-year-olds manifest some cognitive flexibility, but their performance is significantly worse than that of 4- and 5-year-olds. For the 3-year-olds, in reversal tasks, although 80% of the children passed the post-switch phrase in color task; less then 60% children passed the post-switch phrase in shape, number and direction tasks. In extra-dimensional tasks, 3-year-olds performance is worse than that in the reversal tasks. Less than 50% of the children passed the tasks. Children’s cognitive flexibility develops fast from 3-year-olds to 4-year-olds. Both 4-year-olds and 5-year-olds demonstrate high flexibility without significant difference between them. (2) Children’s flexibility in the conceptual domains of shape, color, number and direction follows different developing patterns. In inter-dimensional reversal tasks, 3-year-olds’ performance is not the same in the 4 conceptual domains, but the difference among the domains is insignificant in 4-and-5-year-olds. In extra-dimensional switching tasks, children’s performance on the 4 domain tasks is significantly different from one another in 3-, 4-, and 5-year-olds. (3) The way the stimuli are presented affects children’s development of cognitive flexibility. In inter-dimensional reversal tasks, 3-year-olds’ performance in consecutive presentation is significantly better than that in simultaneous presentation. 4- and 5-year-olds’ performance in the 2 presentations is not significantly different from each other. In extra-dimensional switch tasks, 3-, 4-, and 5-year-olds’ performance in the consecutive presentation is not significantly better than that in the simultaneous presentation (4) 3-, 4-, and 5-year-olds’ self-issued labeling aids their performance on the switching tasks. Children’ performance in the labeling condition is significantly better than that of no labeling. (5) 3-5-year-olds’ cognitive flexibility is highly correlated with their working memory and inhibition. Children’ development of cognitive flexibility is a process that involves activation of working memory and inhibition, in which the complexity of the task also plays a role.

TeO2-Nb2O5-YF3玻璃系统的形成区及性质研究

制备了一种新型的氧卤碲酸盐玻璃：TeO2-Nb2O5-YF3,给出并研究了TeO2-Nb2O5-YF3三元系统的玻璃形成范围。测试了玻璃的密度、折射率、差热(DTA)、拉曼光谱、红外透射光谱以及紫外吸收光谱,通过光谱分析研究了组分含量的变化对玻璃结构及红外透射特性的影响。实验结果表明,TeO2-Nb2O5-YF3玻璃系统具有优良的成玻璃性能和热稳定性等特性,而且在2.8～3.3 μm区域内无明显的[OH]基团吸收,在中红外3～5 μm区域具有优良透射性能,因此在中红外透射方面具有潜在应用价值。