氧化低密度脂蛋白(oxidized low density lipoprotein,oxLDL)被认为是动脉硬化的关键致病因素。文章综合运用紫外吸收光谱、荧光光谱、同步荧光光谱及圆二色(circular dichroism,CD)光谱研究了Cu2+诱导不同时间的LDL体外氧化过程。随着...氧化低密度脂蛋白(oxidized low density lipoprotein,oxLDL)被认为是动脉硬化的关键致病因素。文章综合运用紫外吸收光谱、荧光光谱、同步荧光光谱及圆二色(circular dichroism,CD)光谱研究了Cu2+诱导不同时间的LDL体外氧化过程。随着氧化时间的增加,生成的丙二醛(malonaldehyde,MDA)的量逐渐增加,其相对应的430nm处的荧光强度也随之加强,氧化过程中生成了新的氧化产物。氧化低密度脂蛋白紫外吸收增强;表征氨基酸残基信息的特征荧光强度和同步荧光强度降低;载脂蛋白B-100(apolipoprotein B-100,apoB-100)α-螺旋含量减少。实验结果表明,LDL氧化过程中Cu2+不仅诱导了氧化产物的生成,而且改变了apoB-100的构象进而导致了生色基团的微环境的变化。展开更多
Simulated UV-vis and CD （circular dichroism） spectra were obtained for several chiral Schiff base Ni（II）, Cu（II） and Zn（II） complexes by TD-DFT （time dependent-density functional theory）and Z1NDO calculation...Simulated UV-vis and CD （circular dichroism） spectra were obtained for several chiral Schiff base Ni（II）, Cu（II） and Zn（II） complexes by TD-DFT （time dependent-density functional theory）and Z1NDO calculations. Dipole moments for them were also evaluated by ZINDO calculations and revealed that Cu（II） complexes exhibited the largest values than the analogous Ni（II） and Zn（II） complexes. Although these complexes possessed large dipole moments, induced CD by these complexes were observed a Cu（II）-containing metallodendrimer nor Cu-nanoclusters prepared in a PAMAM （polyamidoamine） dendrimer experimentally nevertheless of other related chiral Schiff base Ni（II）, Cu（II）, and Zn（II） complexes. The present results suggested that steric factors of ligands were more important than electronic factors for emerging induced CD bands by supramolecular interactions.展开更多
氧化修饰低密度脂蛋白(oxidized low density lipoprotein,oxLDL)被认为是动脉硬化的关键致病因素。oxLDL的性能与其唯一的组成蛋白——载脂蛋白B-100(apoB-100)的二级结构即构象密切相关。荧光光谱和圆二色(CD)光谱是研究蛋白质构象的...氧化修饰低密度脂蛋白(oxidized low density lipoprotein,oxLDL)被认为是动脉硬化的关键致病因素。oxLDL的性能与其唯一的组成蛋白——载脂蛋白B-100(apoB-100)的二级结构即构象密切相关。荧光光谱和圆二色(CD)光谱是研究蛋白质构象的有力手段,因此在oxLDL结构的研究中也有广泛的应用。本文综述了近年来荧光光谱和圆二色光谱在LDL氧化研究方面的应用,并对今后的研究方向做了展望。展开更多
Noble metal cocatalysts have shown great potential in boosting the performance of CdS in photocatalytic water splitting.However,the mechanism and kinetics of electron transfer in noble-metal-decorated CdS during pract...Noble metal cocatalysts have shown great potential in boosting the performance of CdS in photocatalytic water splitting.However,the mechanism and kinetics of electron transfer in noble-metal-decorated CdS during practical hydrogen evolution is not clearly elucidated.Herein,Pt-nanoparticle-decorated CdS nanorods(CdS/Pt)are utilized as the model system to analyze the electron transfer kinetics in CdS/Pt heterojunction.Through femtosecond transient absorption spectroscopy,three dominating exciton quenching pathways are observed and assigned to the trapping of photogenerated electrons at shallow states,recombination of free electrons and trapped holes,and radiative recombination of locally photogenerated electron-hole pairs.The introduction of Pt cocatalyst can release the electrons trapped at the shallow states and construct an ultrafast electron transfer tunnel at the CdS/Pt interface.When CdS/Pt is dispersed in acetonitrile,the lifetime and rate for interfacial electron transfer are respectively calculated to be~5.5 ps and~3.5×10^(10) s^(−1).The CdS/Pt is again dispersed in water to simulate photocatalytic water splitting.The lifetime of the interfacial electron transfer decreases to~5.1 ps and the electron transfer rate increases to~4.9×10^(10) s^(−1),confirming that Pt nanoparticles serve as the main active sites of hydrogen evolution.This work reveals the role of Pt cocatalysts in enhancing the photocatalytic performance of CdS from the perspective of electron transfer kinetics.展开更多
Two new chiral Schiff base acacen-derivative nickel（II） and copper（II） complexes have been prepared and characterized with IR, electronic, and CD spectra and X-ray crystallography. So-called artifact peaks of soli...Two new chiral Schiff base acacen-derivative nickel（II） and copper（II） complexes have been prepared and characterized with IR, electronic, and CD spectra and X-ray crystallography. So-called artifact peaks of solid-state CD spectra due to restricted to rotate freely of molecules appeared at about 334 and 460 nm for nickel（II） and copper（II） complexes. Changes of intensity of the peaks have been investigated in different matrices such as solid-state （microcrystals or KBr pellets）, PMMA cast films and acetone solutions of various concentrations and pure acetone solutions. Although restricted orientation of molecules in rigid matrices leads to increase the peak intensity toward negative and positive optical rotation for nickel（II） and copper（II） complexes, respectively, the degree of increasing intensity depends on not concentration but viscosity of polymer solutions. Therefore, the artifact CD peaks of solid-state can act as an indicator of environmental viscosity of soft mater matrices.展开更多
In order to greatly improve adsorption capacity, the diatomite was pillared by polyhydroxyl-aluminum.A series of adsorption tests were conducted to obtain the optimum condition for pillared diatomite synthesis. The sc...In order to greatly improve adsorption capacity, the diatomite was pillared by polyhydroxyl-aluminum.A series of adsorption tests were conducted to obtain the optimum condition for pillared diatomite synthesis. The scanning electron microscopy （SEM）, Fourier transform infrared spectroscopy （FTIR）, surface area and porosity analyzer and micro-electrophoresis were used to determine pore structure and surface property.The pillared diatomite attaining the optimal adsorption densities （qe） of Pb^2＋ and Cd^2＋ was synthesized with the following conditions： Addition of pillaring solution containing Al3＋-oligomers with a concentration range of 0.1-0.2 mol/L to a suspension containing Na＋-diatomite to obtain the required Al/diatomite ratio of 10 mmol/g; synthesis temperature of 80 ℃ for 120 min; aging at a temperature of 105 ℃ for 16 h. The adsorption capacities of Pb^2＋ and Cd^2＋ on pillared diatomite increase by 23.79% and 27.36% compared with natural diatomite, respectively. The surface property of pillared diatomite is more favorable for ion adsorption than natural diatomite. The result suggests that diatomite can be modified by pillaring with polyhydroxyl-aluminum to improve its adsorption properties greatly.展开更多
The hydrotalcite-like compound [Zn2AI（OH）6]NO3-mH20 （shorted as ZnAI-NO3） was intercalated with the chelating agent EDTA （ethylene diamine tetraacetic acid） by anion exchange to uptake cadmium ion from aqueous s...The hydrotalcite-like compound [Zn2AI（OH）6]NO3-mH20 （shorted as ZnAI-NO3） was intercalated with the chelating agent EDTA （ethylene diamine tetraacetic acid） by anion exchange to uptake cadmium ion from aqueous solutions. The materials synthesized in this work were characterized by chemical analysis, FT-IR （fourier transform infrared spectroscopy）, XRD （X-ray powder diffraction） to confirm their properties. In order to investigate the optimum conditions for Cd（II） adsorption, the amount of Cd（ll） adsorbed by Zn-AI LDHs intercalated with EDTA （ZnAI-EDTA） under different conditions （i.e., adsorbent dosage, temperature and contact time） were determined by ICP-AES （inductively coupled plasma-atomic emission spectrometry）. Adsorption isotherms of Cd（II） onto ZnA1-EDTA were measured at varying initial Cd concentrations （0.05 mg/L to 1 mg/L） under optimized conditions. The data were applied to Langmuir and Freundlich isotherms model, and well fitted by the Freundlich isotherms model. The pseudo-second-order kinetic model was more adequate to describe the kinetic in this case.展开更多
文摘Simulated UV-vis and CD （circular dichroism） spectra were obtained for several chiral Schiff base Ni（II）, Cu（II） and Zn（II） complexes by TD-DFT （time dependent-density functional theory）and Z1NDO calculations. Dipole moments for them were also evaluated by ZINDO calculations and revealed that Cu（II） complexes exhibited the largest values than the analogous Ni（II） and Zn（II） complexes. Although these complexes possessed large dipole moments, induced CD by these complexes were observed a Cu（II）-containing metallodendrimer nor Cu-nanoclusters prepared in a PAMAM （polyamidoamine） dendrimer experimentally nevertheless of other related chiral Schiff base Ni（II）, Cu（II）, and Zn（II） complexes. The present results suggested that steric factors of ligands were more important than electronic factors for emerging induced CD bands by supramolecular interactions.
文摘氧化修饰低密度脂蛋白(oxidized low density lipoprotein,oxLDL)被认为是动脉硬化的关键致病因素。oxLDL的性能与其唯一的组成蛋白——载脂蛋白B-100(apoB-100)的二级结构即构象密切相关。荧光光谱和圆二色(CD)光谱是研究蛋白质构象的有力手段,因此在oxLDL结构的研究中也有广泛的应用。本文综述了近年来荧光光谱和圆二色光谱在LDL氧化研究方面的应用,并对今后的研究方向做了展望。
文摘Noble metal cocatalysts have shown great potential in boosting the performance of CdS in photocatalytic water splitting.However,the mechanism and kinetics of electron transfer in noble-metal-decorated CdS during practical hydrogen evolution is not clearly elucidated.Herein,Pt-nanoparticle-decorated CdS nanorods(CdS/Pt)are utilized as the model system to analyze the electron transfer kinetics in CdS/Pt heterojunction.Through femtosecond transient absorption spectroscopy,three dominating exciton quenching pathways are observed and assigned to the trapping of photogenerated electrons at shallow states,recombination of free electrons and trapped holes,and radiative recombination of locally photogenerated electron-hole pairs.The introduction of Pt cocatalyst can release the electrons trapped at the shallow states and construct an ultrafast electron transfer tunnel at the CdS/Pt interface.When CdS/Pt is dispersed in acetonitrile,the lifetime and rate for interfacial electron transfer are respectively calculated to be~5.5 ps and~3.5×10^(10) s^(−1).The CdS/Pt is again dispersed in water to simulate photocatalytic water splitting.The lifetime of the interfacial electron transfer decreases to~5.1 ps and the electron transfer rate increases to~4.9×10^(10) s^(−1),confirming that Pt nanoparticles serve as the main active sites of hydrogen evolution.This work reveals the role of Pt cocatalysts in enhancing the photocatalytic performance of CdS from the perspective of electron transfer kinetics.
文摘Two new chiral Schiff base acacen-derivative nickel（II） and copper（II） complexes have been prepared and characterized with IR, electronic, and CD spectra and X-ray crystallography. So-called artifact peaks of solid-state CD spectra due to restricted to rotate freely of molecules appeared at about 334 and 460 nm for nickel（II） and copper（II） complexes. Changes of intensity of the peaks have been investigated in different matrices such as solid-state （microcrystals or KBr pellets）, PMMA cast films and acetone solutions of various concentrations and pure acetone solutions. Although restricted orientation of molecules in rigid matrices leads to increase the peak intensity toward negative and positive optical rotation for nickel（II） and copper（II） complexes, respectively, the degree of increasing intensity depends on not concentration but viscosity of polymer solutions. Therefore, the artifact CD peaks of solid-state can act as an indicator of environmental viscosity of soft mater matrices.
基金Project(12JJ8016)supported by the Hunan Provincial Natural Science Foundation of ChinaProject(CX2012B317)supported by Hunan Provincial Innovation Foundation For Postgraduate,ChinaProject(2006180)supported by the Hunan Key Discipline Construction Found of Environmental Science,China
文摘In order to greatly improve adsorption capacity, the diatomite was pillared by polyhydroxyl-aluminum.A series of adsorption tests were conducted to obtain the optimum condition for pillared diatomite synthesis. The scanning electron microscopy （SEM）, Fourier transform infrared spectroscopy （FTIR）, surface area and porosity analyzer and micro-electrophoresis were used to determine pore structure and surface property.The pillared diatomite attaining the optimal adsorption densities （qe） of Pb^2＋ and Cd^2＋ was synthesized with the following conditions： Addition of pillaring solution containing Al3＋-oligomers with a concentration range of 0.1-0.2 mol/L to a suspension containing Na＋-diatomite to obtain the required Al/diatomite ratio of 10 mmol/g; synthesis temperature of 80 ℃ for 120 min; aging at a temperature of 105 ℃ for 16 h. The adsorption capacities of Pb^2＋ and Cd^2＋ on pillared diatomite increase by 23.79% and 27.36% compared with natural diatomite, respectively. The surface property of pillared diatomite is more favorable for ion adsorption than natural diatomite. The result suggests that diatomite can be modified by pillaring with polyhydroxyl-aluminum to improve its adsorption properties greatly.
文摘The hydrotalcite-like compound [Zn2AI（OH）6]NO3-mH20 （shorted as ZnAI-NO3） was intercalated with the chelating agent EDTA （ethylene diamine tetraacetic acid） by anion exchange to uptake cadmium ion from aqueous solutions. The materials synthesized in this work were characterized by chemical analysis, FT-IR （fourier transform infrared spectroscopy）, XRD （X-ray powder diffraction） to confirm their properties. In order to investigate the optimum conditions for Cd（II） adsorption, the amount of Cd（ll） adsorbed by Zn-AI LDHs intercalated with EDTA （ZnAI-EDTA） under different conditions （i.e., adsorbent dosage, temperature and contact time） were determined by ICP-AES （inductively coupled plasma-atomic emission spectrometry）. Adsorption isotherms of Cd（II） onto ZnA1-EDTA were measured at varying initial Cd concentrations （0.05 mg/L to 1 mg/L） under optimized conditions. The data were applied to Langmuir and Freundlich isotherms model, and well fitted by the Freundlich isotherms model. The pseudo-second-order kinetic model was more adequate to describe the kinetic in this case.
