Conformations of Unfolded S. cerevisiae Cytochrome c Probed by Fluorescence Energy Transfer Kinetics

Employing fluorescence energy transfer kinetics, we have shown that substantial populations of compact molecules are present in GuHCl-denatured CX-dansyl-labeled (X = 39, 85, 102) S. cerevisiae iso-1 cytochrome c. Fully 40% of unfolded molecules are in compact conformations in the C39 protein.     

荧光猝灭反应的动力学

荧光猝灭反应的动力学阮复昌＊＊李向明＊＊＊莫炳禄公国庆邓颂九（华南理工大学化学工程研究所，广州５１０６４１）关键词荧光猝灭动力学分析高分子半透膜光学传感器１前言生物传感器是生物工程的一个重要分支，近年来愈来愈引起人们的重视［１，２］。它不仅可以对细...     

Fluorescence Quenching in Benzene Vapor

The fluorescence quenching in benzene vapor is investigated, using lifetime measurements. The self-quenching reaction is studied at various temperatures and the activation energy for this process is determined to be 950 cm^?1. The effect of some simple gases on the fluorescence lifetime is also studied.     

荧光猝灭法测定痕量铜

在HCl介质中和α,α-联吡啶存在下,α,α′-联吡啶可活化Cu^2＋催化H2O2氧化1,4-二羟基-9,10-葸醌转化无荧光化合物,导致体系荧光急剧猝灭,据此建立了催化H2O2氧化1,4-二羟基-9,10-蒽醌荧光猝灭法测定痕量铜的新方法。     

Electron Transfer Kinetics on Boron-Doped Diamond Part I: Influence of Anodic Treatment

Boron-doped diamond electrodes, both as-grown and polarized anodically under different conditions, were prepared in order to study the chemical and electrochemical changes of diamond and clarify the role played by the surface-state density. Many different treatments were employed: as-grown (BDD_ag), mildly polarized (BDD_mild), strongly polarized in perchloric acid (BDD_severerpar;, and strongly polarized in a sulphuric acid-acetic acid mixture (BDD_AcOHrpar;. Charge transfer processes at the electrode surface were studied by cyclic voltammetry. Simple electron transfer processes such as the outer-sphere redox system ferri/ferrocyanide (Fe^III/II;(CN)₆rpar; and complex charge transfer reactions such as the inner-sphere 1,4-benzoquinone/hydroquinone (Q/H₂Q) redox reaction were chosen to test the electrochemical properties of the electrodes. The properties of the diamond electrodes were found to undergo strong modification as a function of surface treatment. The active surface area and the reaction rate constants decreased significantly upon anodic polarization. Important drops in the charge carrier concentration on the surface and in true surface area led to hindrance of electron transfer at the electrode.     

Chemical Glycosylation by Single Electron Transfer

Oligosaccharides play important roles in nature; however, chemical synthesis of oligosaccharides is still difficult and not carried out in a fully automated manner. Among various methods, the activation of glycosyl donors by single electron transfer using electrochemical and photochemical methods has several benefits. In particular, electrochemical oxidation is a powerful method to activate glycosyl donors, including thioglycosides, which are one of the most popular class of glycosyl donors in modern chemical glycosylations. This review article covers the pioneering works of electrochemical glycosylations, other chemical glycosylations achieved by single electron transfer, and our recent approach to the automated solution-phase synthesis of oligosaccharides based on the electrochemical method.     

Electric Field Induced Fluorescence Modulation of Single Molecules in PMMA Based on Electron Transfer

We present a method to modulate the fluorescence of non-polar single squaraine-derived rotaxanes molecules embedded in a polar poly(methyl methacrylate) (PMMA) matrix under an external electric field. The electron transfer between single molecules and the electron acceptors in a PMMA matrix contributes to the diverse responses of fluorescence intensities to the electric field. The observed instantaneous and non-instantaneous electric field dependence of single-molecule fluorescence reflects the redistribution of electron acceptors in PMMA induced by electronic polarization and orientation polarization of polar polymer chains in an electric field.     

Fluorescence Quenching of Tyrosine-Ag Nanoclusters by Metal Ions: Analytical and Physicochemical Assessment

A new synthesis method is described for the first time to produce silver nanoclusters (AgNCs) by using the tyrosine (Tyr) amino acid. Several important parameters (e.g., molar ratios, initial pH, reaction time etc.) were optimized to reach the highest yield. The formed Tyr-AgNCs show characteristic blue emission at λ_em = 410 nm, and two dominant fluorescence lifetime components were deconvoluted (τ₁ ~ 3.7 and τ₂ ~ 4.9 ns). The NCs contained metallic cores stabilized by dityrosine. For possible application, the interactions with several metal ions from the tap water and wastewater were investigated. Among the studied cations, four different ions (Cu²⁺, Ni²⁺, Fe³⁺, and Rh³⁺) had a dominant effect on the fluorescence of NCs. Based on the detected quenching processes, the limit of detection of the metal ions was determined. Static quenching (formation of a non-luminescent complex) was observed in all cases by temperature-dependent measurements. The calculated thermodynamic parameters showed that the interactions are spontaneous ranked in the following order of strength: Cu²⁺ > Fe³⁺ > Rh³⁺ > Ni²⁺. Based on the sign and relations of the standard enthalpy (ΔH°) and entropy changes (ΔS°), the dominant forces were also identified.     

荧光光谱研究吡虫啉与牛血清白蛋白的相互作用

运用荧光光谱、紫外光谱法研究了农药吡虫啉与牛血清白蛋白(BSA)的相互作用。实验结果表明,农药分子与BSA形成基态复合物导致BSA内源荧光猝灭,猝灭机理主要为静态猝灭和非辐射能量转移。测定了不同温度下该反应的表观结合常数KA、结合位点数n及结合热力学参数,热力学参数的变化表明上述作用过程是自由能降低的自发分子间作用过程,农药分子与BSA之间以氢键和范德华作用力为主;根据F rster能量转移理论,测得供体与受体间结合距离r与能量转移效率E;并用同步荧光技术考察了农药分子对BSA构象的影响。     

牛血清白蛋白荧光猝灭测定药物中的头孢孟多酯

应用牛血清白蛋白（BSA）荧光猝灭法建立了一种测定药物中头孢孟多酯（CEF）含量的新方法。牛血清白蛋白具有很强的内源荧光性,而头孢孟多酯溶液本身不产生荧光。当头孢孟多酯与BSA结合后,会导致其荧光强度下降。牛血清蛋白在λex=340 nm处的荧光猝灭程度与头孢孟多酯的量在一定浓度范围内呈良好的线性关系,据此建立测定药品中头孢孟多酯含量的新方法。该结合物的最大发射波长为λmax=340 nm,与头孢孟多酯物质的量浓度在2.18×10^-6~2.62×10^-5 mol·L-1范围内线性关系良好。其线性回归方程为ΔF=2.42×10^7CCEF-35.155,相关系数r=0.996 9,检出限为8.582 58×10-7 mol·L-1,RSD为0.16%,加标回收率为94.67%~98.43%。本方法操作简便、快速,用于实际样本的测定,结果满意。     

CdTe/CdS量子点荧光猝灭法测定盐酸西替利嗪

建立一种基于纳米材料的荧光性质测定盐酸西替利嗪含量的新方法,盐酸西替利嗪能使硫化镉包被的碲化镉核壳型量子点(CdTe/CdS QDs)发生规律性的荧光猝灭,研究二者相互作用的最佳条件,从而建立测定盐酸西替利嗪含量的方法。结果表明:盐酸西替利嗪的浓度在0.40~42μg/m L范围内有良好的线性关系(r=0.9992),检测限为2.50×10-2μg/m L,回收率为93.80%~97.00%。结论:此方法简便、快捷、可靠,适用于盐酸西替利嗪的含量测定。     

Quenching of Protein Fluorescence by Fullerenol C60(OH)36 Nanoparticles

The effect of the interaction between fullerenol C₆₀(OH)₃₆ (FUL) and alcohol dehydrogenase (ADH) from Saccharomyces cerevisiae and human serum albumin (HSA) was studied by absorption spectroscopy, fluorescence spectroscopy, and time-resolved fluorescence spectroscopy. As shown in the study, the fluorescence intensities of ADH and HSA at excitation wavelengths λ_ex = 280 nm (Trp, Tyr) and λ_ex = 295 nm (Trp) are decreased with the increase in the FUL concentration. The results of time-resolved measurements indicate that both quenching mechanisms, dynamic and static, are present. The binding constant K_b and the number of binding sites were obtained for HSA and ADH. Thus, the results indicated the formation of FUL complexes and proteins. However, the binding of FUL to HSA is much stronger than that of ADH. The transfer of energy from the protein to FUL was also proved.     

厄贝沙坦荧光猝灭法测定化妆品中痕量汞

依据汞对厄贝沙坦的荧光具有猝灭的特性,建立了一种测定痕量汞的新方法。该方法的最大激发波长为280nm,最大发射波长为377nm,线性范围为0.04～0.60mg/L,相关性系数为0.9980,检出限为0.0139 mg/L,对于0.13 mg/L汞标准溶液测定10次的相对标准偏差为0.415%。该方法用于化妆品中痕量汞的测定,结果令人满意。     

Calculation of the Heat Transfer in Coke Dry Quenching by Numerical Modeling

The air flow and heat transfer in a coke dry quenching (CDQ) system are analyzed by simulation using FloEFD software, within the framework of a modified k–ε model of turbulence. The calculated temperatures are compared with operational data. The accuracy of the simulation is acceptable. The proposed method may be used for engineering calculations in the design and refinement of CDQ systems or their components, with significant decrease in experiment costs.     

硫代乙酰胺对川芎嗪-CuI荧光材料的荧光猝灭作用

以川芎嗪和碘化亚铜为原料,合成了一种新型的黄色固体配合物,优化了合成条件,并得到配合物的荧光光谱。结果表明:川芎嗪-CuI黄色固体配合物对硫代乙酰胺具有快速响应的可视化识别。当加入硫代乙酰胺后,川芎嗪-CuI不断溶解,并由黄色变为无色,荧光消失。     

电子活化再生原子转移自由基聚合的研究进展

原子转移自由基聚合是一种新兴的活性/可控聚合方法,AGET ATRP是在ATRP的基础上改进而发展起来的活性聚合方法。介绍了AGET ATRP的基本机理及研究进展,以及所用催化剂、引发剂、还原剂的研究情况,并展望了其发展前景。     

三苯二噁嗪荧光染料的合成与电子光谱性能

本文以４－氨基－４’－苯基二苯醚和４－氨基－２’－苯基二苯醚与四氯苯醌反应,合成了两个新结构三苯二嗪荧光染料。在五种溶剂中测定了它们的吸收及荧光光谱,并讨论了溶剂极性对染料荧光光谱影响。