Binding of triclosan to human serum albumin: insight into the molecular toxicity of emerging contaminant

Purpose

The interaction between triclosan (TCS) and human serum albumin (HSA) was investigated in order to obtain the binding mechanism, binding constant, the type of binding force, the binding distance between the donor and acceptor, and the effect of TCS on the conformation change of HSA.

Methods

A HSA solution was added to the quartz cell and then titrated by successive addition of TCS. The fluorescence quenching spectra and synchronous spectra were recorded with the excitation and emission slits of the passage of band set at 10 and 20 nm. Three-dimensional fluorescence spectra of HSA were recorded before and after the addition of TCS. The capillary electrophoresis was conducted with the pressure injection mode at 0.5 psi for 5 s, separation under 25 kV, and detection at 214 nm.

Results

Fluorescence data indicated the fluorescence quenching of HSA by TCS was static quenching, and the quenching constants (K _a ) were 1.14?×?10⁵, 8.75?×?10⁴, 6.67?×?10⁴, and 5.00?×?10⁴ at 293, 298, 303, and 309 K, respectively. The thermodynamic parameters, enthalpy change (??H) and entropy change (??S) for the interaction were calculated to be ?37.9 kJ mol^?1 and 32.6 J?mol^?1 K^?1. The binding distance between TCS and tryptophan residues of HSA was obtained to be 1.81 nm according to F??rster nonradioactive energy transfer theory. The UV-Vis absorption spectroscopy, the synchronous fluorescence spectroscopy, three-dimensional fluorescence spectroscopy, and circular dichroism spectroscopy revealed the alterations of HSA secondary structure in the presence of TCS. Finally, the interaction between TCS and HSA was further confirmed by capillary electrophoresis.

Conclusions

TCS was bound to HSA to form the TCS-HSA complex, with the binding distance of 1.81 nm. Hydrophobic interaction and hydrogen bond were dominated in the binding. TCS could change the secondary conformation of HSA. This work provides an insight into noncovalent interaction between emerging pollutants and protein, helping to elucidate the toxic mechanism of such pollutants.     

Insights into the nature of secondary organic aerosol in Mexico City during the MILAGRO experiment 2006

This study targets understanding the secondary sources of organic aerosol in Mexico City during the Megacities Impact on Regional and Global Environment (MIRAGE) 2006 field campaign. Ambient PM_2.5 was collected daily at urban and peripheral locations. Particle-phase secondary organic aerosol (SOA) products of anthropogenic and biogenic precursor gases were measured by gas chromatography mass spectrometry. Ambient concentrations of SOA tracers were used to estimate organic carbon (OC) from secondary origins (SOC). Anthropogenic SOC was estimated as 20–25% of ambient OC at both sites, while biogenic SOC was less abundant, but was relatively twice as important at the peripheral site. The OC that was not attributed secondary sources or to primary sources in a previous study showed temporal consistency with biomass-burning events, suggesting the importance of secondary processing of biomass-burning emissions in the region. The best estimate of biomass-burning-related SOC was in the range of 20–30% of ambient OC during peak biomass burning events. Low-molecular weight (MW) alkanoic and alkenoic dicarboxylic acids (C₂–C₅) were also measured, of which oxalic acid was the most abundant. The spatial and temporal trends of oxalic acid differed from tracers for primary and secondary sources, suggesting that it had different and/or multiple sources in the atmosphere.     

Comparison of retention and output of sulfur in limestone soil and yellow soil and their responses to acid deposition in a small karst catchment of Guizhou Province,Southwest China

Environmental Science and Pollution Research - Investigating the responses of retention and output of sulfur (S) is significant to understand the impact of atmospheric S deposition on the S cycling...     

青海油田采油一厂采出水处理技术改进

尕斯库勒联合站采出水治理是青海油田采油一厂环境保护的一项重要工作。为了对油田采出水进行综合治理,尕斯库勒联合站先后对原有的采出水处理系统进行了四次技术改造,通过多年的实践与探索,找到了满足青海油田采出水处理需求较为成熟的采出水处理技术。     

港口环境风险管理探——以天津港为例

中国是一个海洋大国,海洋和港口的环境保护得到了国家的高度重视.港口的环境风险防范管理是一个较新的研究领域,当前中国港口经济的高速增长必然带来港口环境风险的增加,对风险进行有效地评价和管理对国家的经济发展和环境保护具有重要意义.本文对天津港环境风险管理的过程进行了较为系统的探讨,分析了天津港环境风险管理技术思路和主要内容,对天津港存在的环境风险因子做了识别,并对环境风险的评估方法做了针对性总结,为港口的风险防范措施提供了一些建议.     

SmMnO3钙钛矿型氧化物的制备及其催化氧化甲苯性能

采用溶胶-凝胶法制备了SmMnO3钙钛矿型氧化物,将其作为催化剂,在固定床反应器中研究了催化剂的焙烧温度和混合气体积空速对甲苯催化氧化效果的影响,并通过XRD、SEM、XPS、H2-TPR等技术表征了催化剂的微结构及化学性质.结果表明:催化剂对甲苯的催化氧化活性随焙烧温度升高而提高;焙烧温度为800℃时制备的催化剂(S...     

MIP系统在某挥发性氯代烃污染地块调查中的应用

针对我国挥发性有机污染地块调查评估中存在的采样缺失、成本高及周期长等问题,选择华北地区某挥发性氯代烃污染地块为研究对象,采用现行调查方法与基于膜界面探针(MIP)系统快速调查技术联合使用的方式,现场完成场地钻探调查点位4个(土壤样品36个),MIP系统调查点位11个(验证点位4个),以研究MIP验证点位检测电信号值与其...     

关于“十五”期间区域发展战略的建议

我国区域发展面临的的主要问题包括：地区发展差距扩大,国土整治和促进区域可持续发展的工作需要加强,失业高发地区的就业压力亟需缓解,扶贫开发工作仍需坚持等。在制定地区发展战略时,应当灾行”效率与公平兼顾”,加快规范的财政转移支付制度的建立,充分运用金融工具,实行地区差别的金融调控政策,尽快着手地区发展立法,选准西部大开发重点开发区,以大河流域作为重要切入点重视开展国土整治工作,抑制人口数量增长,提高人     

硝酸盐浓度对微生物燃料电池阳极产电性能的影响

采用以假单胞菌Pseudomonas sp.C27为阳极优势菌属的微生物燃料电池(MFC)为研究对象,重点考察了进水中的硝酸盐浓度对于MFC系统产电及污染物去除的影响.实验结果表明,硝酸盐对于MFC的库仑效率(CE)影响较大,当硝酸盐浓度为250 mg·L~(-1)时,其电压下降段库仑效率仅为0.17%,而阳极未加入硝酸盐时,库仑效率为9.3%.当阳极初始硝酸盐浓度由0 mg·L~(-1)增加到250 mg·L~(-1)时,系统的传荷内阻由16.3Ω下降至11.2Ω,输出电压经短暂的电压下降后迅速回升至稳定,其稳定阶段输出电压与未受抑制阶段基本持平,最大输出功率可达到120 m W·m~(-2)左右.当硝酸盐浓度大于300 mg·L~(-1)时,硝酸盐对阳极微生物产电活性造成不可逆的抑制作用,系统产电能力大幅度下降且无法恢复至未受抑制阶段.可见,阳极生物反硝化过程对阳极生物产电具有电子竞争作用,过高的硝酸盐浓度会造成阳极生物膜产电性能降低甚至完全丧失.     

Size distribution of polycyclic aromatic hydrocarbons in urban and suburban sites of Beijing, China

PAHs in five-stage size segregated aerosol particles were investigated in 2003 at urban and suburban sites of Beijing. The total concentration of 17 PAHs ranged between 0.84 and 152 ng m(-3), with an average of 116 ng m(-3), in urban area were 1.1-6.6 times higher than those measured in suburban area. It suggested a serious pollution level of PAHs in Beijing. PAHs concentrations increased with decreasing the ambient temperature. Approximately 68.4-84.7% of PAHs were adsorbed on particles having aerodynamic diameter 2.0 microm. Nearly bimodal distribution was found for PAHs with two and three rings, more than four rings PAHs, however, followed unimodal distribution. The overall mass median diameter (MMD) for PAHs decreased with increasing molecular weight. Diagnostic ratios and normalized distribution of PAHs indicated that the PAHs in aerosol particles were mainly derived from fossil fuel combustion. Coal combustion for domestic heating was probably major contributor to the higher PAHs loading in winter, whereas PAHs in other seasons displayed characteristic of mixed source of gasoline and diesel vehicle exhaust. Biomass burning and road dust are minor contributors to the PAHs composition of these aerosol particles. Except for source emission, other factors, such as meteorological condition, photochemical decay, and transportation from source to the receptor site, should to be involved in the generation of the observed patterns.