采用荧光光谱、紫外-可见光谱研究了有/无金属Zn2+存在下甲基百里酚蓝(MTB)与牛血清白蛋白(BSA)的相互作用.实验结果表明,无论Zn2+离子存在与否,MTB与BSA之间均为一形成复合物的静态猝灭过程.根据Stern-Volmer方程和Lineweaver-Burk方程求出了其结合常数与热力学参数,发现Zn2+离子存在时,MTB与BSA间的作用力由静电力转为氢键和Van der Waals力作用为主,认为金属Zn2+以"离子架桥"的方式参与MTB与BSA的结合过程,从而ΔH对ΔG的贡献增大. 相似文献
A rapid and efficient synthesis of novel dendrimer homotriptycenes is presented. The dendronized 9,10-dihydroanthracen-9-ols 4, having high electron densities in the benzene rings of the Fréchet-type dendrons, exhibited in the presence of acid a quantitative transannular ring closure to the corresponding dendritic homotriptycenes. The electron-donating Fréchet-type dendrons enabled the intramolecular FC alkylation by a regioselective 1,7-elimination of H2O. 相似文献
Complexing polymer‐coated electrodes have been synthesized by oxidative electropolymerization of ethylenediamine tetra‐N‐(3‐pyrrole‐1‐yl)propylacetamide (monomer L ). The presence of four polymerizable pyrrole fragments on the same EDTA skeleton was thought to confer enhanced rigidity and controlled dimensionality to the resulting complexing materials, which were used for the electrochemical detection of Hg(II), Cu(II), Pb(II) and Cd(II) ions by means of the chemical preconcentration‐anodic stripping technique. The polyamide electrode material showed particularly a significant selectivity towards mercury ions, even in the presence of a large excess of other metal cations. Moreover, the use of imprinted polymer‐coated electrodes prepared by electropolymerization of L in the presence of metal cations turned out to significantly improve the detection limits, down to 5×10?10 mol L?1 for Hg(II) and Cu(II) species. 相似文献
The rate constants and product ion branching ratios were measured for the reactions of various small negative ions with O2(X 3Σg−) and O2(a 1Δg) in a selected ion flow tube (SIFT). Only NH2− and CH3O− were found to react with O2(X) and both reactions were slow. CH3O− reacted by hydride transfer, both with and without electron detachment. NH2− formed both OH−, as observed previously, and O2−, the latter via endothermic charge transfer. A temperature study revealed a negative temperature dependence for the former channel and Arrhenius behavior for the endothermic channel, resulting in an overall rate constant with a minimum at 500 K. SF6−, SF4−, SO3− and CO3− were found to react with O2(a 1Δg) with rate constants less than 10−11 cm3 s−1. NH2− reacted rapidly with O2(a 1Δg) by charge transfer. The reactions of HO2− and SO2− proceeded moderately with competition between Penning detachment and charge transfer. SO2− produced a SO4− cluster product in 2% of reactions and HO2− produced O3− in 13% of the reactions. CH3O− proceeded essentially at the collision rate by hydride transfer, again both with and without electron detachment. These results show that charge transfer to O2(a 1Δg) occurs readily if the there are no restrictions on the ion beyond the reaction thermodynamics. The SO2− and HO2− reactions with O2(a) are the only known reactions involving Penning detachment besides the reaction with O2− studied previously [R.S. Berry, Phys. Chem. Chem. Phys., 7 (2005) 289–290]. 相似文献
A novel and sensitive electrochemical method for determination of mercury (II) ions (Hg2+) based on the formation of thymine–Hg2+–thymine complexes and gold nanoparticle-mediated signal amplification is reported. Two 5′ end thiolated complementary oligonucleotides containing six strategically placed thymine–thymine mistakes were introduced in this work. One of the two oligonucleotides was immobilized on a gold electrode and the other one on gold nanoparticles (AuNPs). Due to six thymine–thymine mistakes the two oligonucleotides were not able to be hybridized, so AuNPs could not be immobilized onto the electrode surface after the electrode was immersed in the DNA–AuNPs solution. However, if Hg2+ existed, T–Hg2+–T complexes could be formed and AuNPs could be immobilized onto the electrode surface. Meanwhile, large numbers of [Ru(NH3)6]3+ molecules as electrochemical species could be localized onto the electrode surface. The Hg2+ detection limit of this assay could be as low as 10 nM, which is the US Environmental Protection Agency (EPA) limit of Hg2+ for drinkable water. This method is proven to be simple, convenient, high sensitive and selective. 相似文献
Prediction of lg k = s ( N + E ) verified : In contrast to previous statements, ordinary α,β‐unsaturated iminium ions do react with sulfur ylides. Electrostatic interactions accelerate the reactions by a factor of more than 105 and are responsible for the high stereoselectivity.
A Powerful Luminophore that comprises a centered pyrene acceptor with peripheral amine multidonors is described by J. S. Kim and co‐workers in their Communication on page 2522 ff. The electrochemiluminescence (ECL) efficiency and radical stability of pyrene, a poor ECL luminophore, is markedly improved as the number of peripheral multidonor units is increased in a series of compounds. The ECL enhancement was rationalized by photophysical and electrochemical studies, and theoretical calculations.