Real-Time Study of Genomic DNA Structural Changes upon Interaction with Small Molecules Using Dual-Polarization Interferometry

The structural changes of genomic DNA upon interaction with small molecules have been studied in real time using dual-polarization interferometry (DPI). Native or thermally denatured DNA was immobilized on the silicon oxynitride surface via a preadsorbed poly(ethylenimine) (PEI) layer. The mass loading was similar for both types of DNA, however, native DNA formed a looser and thicker layer due to its rigidity, unlike the more flexible denatured DNA, which mixed with PEI to form a denser and thinner layer. Ethidium bromide (EtBr), a classical intercalator, induced the large thickness decrease and density increase of native DNA (double-stranded), but a slight increase in both the thickness and density of denatured DNA (partial single-stranded).

Sensitive detection of protein by an aptamer-based label-free fluorescing molecular switch

We report an aptamer-based method for the sensitive detection of proteins by a label-free fluorescing molecular switch (ethidium bromide), which shows promising potential in making protein assay simple and economical.

Triplex selective 2-(2-naphthyl)quinoline compounds: Origins of affinity and new design principles

A novel competition dialysis assay was used to investigate the structural selectivity of a series of substituted 2-(2-naphthyl)quinoline compounds designed to target triplex DNA. The interaction of 14 compounds with 13 different nucleic acid sequences and structures was studied. A striking selectivity for the triplex structure poly dA:[poly dT](2) was found for the majority of compounds studied. Quantitative analysis of the competition dialysis binding data using newly developed metrics revealed that these compounds are among the most selective triplex-binding agents synthesized to date. A quantitative structure-affinity relationship (QSAR) was derived using triplex binding data for all 14 compounds used in these studies. The QSAR revealed that the primary favorable determinant of triplex binding free energy is the solvent accessible surface area. Triplex binding affinity is negatively correlated with compound electron affinity and the number of hydrogen bond donors. The QSAR provides guidelines for the design of improved triplex-binding agents.

Identification and characterization of the AcrR/AcrAB system of a pathogenic Edwardsiella tarda strain

Edwardsielia tarda is one of the leading marine pathogens that can infect a wide range of cultured marine species. In this study, the acrR-acrAB cluster was cloned from TX1, a pathogenic E. tarda strain isolated from diseased fish. AcrR and AcrAB were found to be involved in resistance against acriflavine and methyl viologen, which positively regulate the expression of acrAB. AcrR negatively regulates its own expression and the expression of the acrAB operon, most likely by interacting with a 24-bp operator site that overlaps the putative promoter of acrA (PacrA). The repressive effect of AcrR on PacrA could be relieved by acriflavine, methyl viologen, and ethidium bromide, the presence of each of which enhanced transcription from PacrA. Interruption of the regulated expression of acrR by introducing into TX1 a plasmid that overexpresses acrR affected growth under stress conditions, AI-2 production, and bacterial virulence. In addition, mutational analyses identified a constitutively active AcrR mutant (named N215), which exhibits full repressor activity but is impaired in its ability to interact with the inducer. Overexpression of N215 produced the same kind of but moderately stronger effect on TX1 compared to that produced by overexpression of the wild-type acrR.

迟缓爱德华氏菌两种保护性抗原及AcrAB耐药系统的分析

迟缓爱德华氏菌是危害水产养殖业发展的重要病原菌之一，因而其免疫防治研究具有重要意义。论文分析了9种具有保护潜能的迟缓爱德华氏菌蛋白，经过牙鲆免疫保护实验，筛选出EseD和Et18两种有显著性保护效应的抗原。为了提高其保护效应，论文使用基因工程技术将这两种抗原融合到一起，构建重组融合蛋白EEH。结果表明，融合蛋白EEH保护效应较EseD和Et18分别免疫时有所提高。ELISA和Western blotting 结果显示，三种蛋白都能诱导牙鲆产生特异抗体。这些研究为开发迟缓爱德华氏菌疫苗提供了理论基础。 论文克隆分析了迟缓爱德华氏菌AcrAB耐药系统，采用定点突变确定了acrAB、acrR的启动子序列和AcrR在acrAB启动子的结合位点。启动子分析显示，AcrR对acrAB启动子有300倍抑制效应, 对acrR启动子有3倍抑制效应。定点突变显示，K39和R45对AcrR功能具重要性；缺失突变表明，N端205个氨基酸残基是其功能必需。实验筛选出Acriflavine、Ethidium Bromide、Methyl Viologen、Sodium Dodecyl Sulfate等四种AcrR诱导物。分析AcrR过量表达菌株结果显示，其耐药性、生长状况和毒力水平较阴性对照组降低。这些研究加深了我们对迟缓爱德华氏菌耐药机制及其与毒力关系的了解。

Water solubility enhancement of phthalates by cetyltrimethylammonium bromide and beta-cyclodextrin

Water solubility enhancements of six phthalates (five aliphatic phthalates and one phenyl phthalate) by cetyltrimethylammonium bromide (CTAB) and beta-cyclodextrin (beta-CD) were studied at 25 degreesC. The solubilities of these plithalates are remarkably enhanced by CTAB solutions above the critical micelle concentration (cmc). Only marginal enhancement of phthalate solubility was observed in solutions containing CTAB below its cmc and beta-CD at low concentrations (less than 5 mM). The solubility enhancements of the plithalates are proportional to the added amount of CTAB and beta-CD. Partition coefficients of the plithalates between monomeric CTAB surfactant and water (K-MN) and between CTAB micelle and water K-MC) were estimated from the experimental data. The mechanisms of solubility enhancements by CTAB and beta-CD were discussed. A log-linear equation was proposed and evaluated for the solubilization by CTAB below cmc, while the previously proposed linear partitioning model was questioned. The structures of the complexes formed between plithalates and beta-CD were proposed, and the formation constants were estimated. The values of log K-MC, log K-MN, and log Kbeta-CD of the plithalates were found to correlate linearly with the log K-OW of plithalates, with the exception of the solid phenyl phthalate.

Corrosion inhibition of carbon steel in tetra-n-butylammonium bromide aqueous solution by benzotriazole and Na3PO4

The corrosion inhibition behavior of benzotriazole, Na3PO4 and their mixture on carbon steel in 20 wt.% (0.628 mol l(-1)) tetra-n-butylammonium bromide aerated aqueous solution was investigated by weight-loss test, potentiodynamic polarization measurement, electrochemical impedance spectroscopy and scanning electron microscope/energy dispersive X-ray techniques. The inhibition action of BTA or SP or inhibitors mixture on the corrosion of carbon steel is mainly due to the inhibition of anodic process of corrosion. The results revealed that inhibitors mixtures have shown synergistic effects at lower concentration of inhibitors. At 2 g l(-1) BTA and 2 g l(-1) SP showed optimum enhanced inhibition compared with their individual effects.

Clathrate Dissociation Conditions for Methane + Tetra-n-butyl Ammonium Bromide (TBAB) + Water

Hydrate equilibrium data of the CH4 + tetra-n-butyl ammonium bromide (TBAB) + water have been measured by using the isothermal pressure search method for four components of TBAB aqueous solutions. The three-phase equilibrium lines obtained in the present study are shifted to the low-temperature or high-pressure side from that of the stoichiometric TBAB solution. Moreover, methane uptake into semi-clathrates is confirmed by a shift in the clathrate regions when methane is present. The experiments are carried out in the pressure range of (0.5 to 11) MPa and in the temperature range of (281.15 to 295.15) K.

Coating Didodecyldimethylammonium Bromide onto Au Nanoparticles Increases the Stability of Its Complex with DNA

The stability of the complex of cationic lipid with nucleic acid, especially when facing serum, is crucial for the efficiency of gene delivery. Here, we demonstrated that the stability of the complex of didodecyldimethylammonium bromide (DDAB, a cationic lipid) with DNA in the presence of serum dramatically increased after coating DDAB onto the surface of the gold nanoparticles. The stability of the complex was demonstrated with dye intercalation assay, and agarose gel electrophoresis.