Concepts of photochemical damage of Photosystem II and the role of excessive excitation

Photoinhibition is one of the most controversial topics in photophysiology. Well into the 21 st century, scientists have not agreed on the mechanism of action, primary site, and roles of excess energy absorbed by photosynthetic pigments. It is recognized that Photosystem II is the most fragile component during photoinhibition and that excess excitation absorbed by the photosynthetic pigments has a strong impact on it. Consensus is yet to come on terminology, guidelines to study photoinhibition, or boundaries of what can be considered photodamage. Some of these controversies are the result of how we understand the phenomenon of photoinhibition, as this is what determines a given experimental design. Thus, how we understand photodamage depends on the philosophical approach of each group. While some efforts have been made in the parametrization of Photosystem II photoinhibition, an updated review about the concepts of photoinhibition of Photosystem II and how to study it is still pending. In this work, a review of the concepts used in the field of photoinhibition is presented, accompanied by a synopsis on the history and mechanisms of action.     

Tuning the properties of a black TiO2-Ag visible light photocatalyst produced by a rapid one-pot chemical reduction

A highly efficient black TiO₂-Ag photocatalytic nanocomposite, active under both UV and visible light illumination, was synthesized by decorating the surface of 25 nm TiO₂ particles with Ag nanoparticles. The material was obtained via a rapid, one-pot, simple (surfactant and complexing agent free) chemical reduction method using silver nitrate and formaldehyde as a metal salt and reducing agent, respectively. The nanocomposite shows an increase of over 800% in the rate of photocatalytic methylene blue dye degradation, compared to commercial unmodified TiO_2, under UV-VIS illumination. Unlike pure TiO₂, the nanocomposite exhibits visible light activation, with a corresponding drop in optical reflectance from 100% to less than 10%. The photocatalytic properties were shown to be strongly enhanced by post-reduction annealing heat treatments in air, which were observed to decrease, rather than coarsen, silver particle size, and increase particle distribution. This, accompanied by a variation in the silver surface oxidation states, appear to dramatically affect the photocatalytic efficiency under both UV and visible light. This highly active photocatalyst could have wide ranging applications in water and air pollution remediation and solar fuel production.     

Synthesis of UiO-66 with addition of HKUST-1 for enhanced adsorption of RBBR dye

Toxic dye removal, one of the most serious and common industrial pollutants released into natural water, is a critical issue for modern civilization. In this study, a series of UiO-66 composites was synthesized with addition of HKUST-1 using solvothermal method, which was used to remove RBBR dye. The structure, morphology and surface area of the composites were studied by several analyses. HK(5)/UiO-66 possessed a specific surface area of 557.63 m²/g and showed an adsorption capacity of 400 mg/g, higher than that of UiO-66 (261.92 mg/g) with a contact time of 50 min. Several adsorption parameters that influenced RBBR removal efficiency were investigated, such as pH, initial dye concentrations, and temperature. All the composites followed pseudo-first order kinetics and Langmuir isotherm adsorption. Moreover, the adsorption process occurred exothermically and spontaneously, indicating that the adsorption process was advantageous in terms of energy. The possible adsorption mechanism and cost analysis of the adsorbent were also studied in detail.     

无封胶白光数码管荧光粉转换率的分析

研究无封胶白光数码管衰减机理,利用蓝白比拟法测算无封胶白光数码管荧光粉转换率.对蓝白数码管分3组进行电流老化实验,老化电流分别为20、40mA和60mA.在恒定直流为20mA,老化时间为1000h实验中,通过分析蓝、白数码管光谱曲线的变化,研究了蓝光光输出功率和黄光光输出功率衰减情况,利用实验数据,分析表明了荧光粉转换率的衰减是影响无封胶白光数码管老化的重要因素.同时分析比较了在40mA和60mA不同电流老化实验下得到的荧光粉转换率,发现工作电流越大,荧光粉转化率衰减越快,符合无封胶白光数码管在大电流作用下衰减更快的实际情况,影响使用寿命.对荧光粉转换率的研究将为无封胶白光数码管的应用及进一步研究无封胶白光数码管衰减原因提供参考.     

甲苯胺蓝动力学分光光度法测定药品中的抗坏血酸

基于在磷酸介质中,抗坏血酸可学原甲苯胺蓝并使其退色反应,建立了一和睦这分光光度法测定了抗坏血酸的新方法。该方法线性范围０－１２０μｇ／ｍＬ,检出限２５μｇ／ｍＬ。用于药品中抗坏血酸的测定,并进行回收试验,回收率在８７－９８％。     

Electrophoretic isolation of membrane proteins from acrylamide gels

Protocols for the optimal resolution of membrane and watersoluble proteins in SDS-denatured state (Tricine SDS-PAGE and Blue Tricine SDS-PAGE; Laemmli SDS-PAGE and Blue Laemmli SDSPAGE) and in the native state (Blue Native PAGE) are presented. The protocols for protein recovery from these gels include techniques of electroelution and electroblotting optimized to the type of the preceding electrophoresis system. Native and denatured proteins thus are obtainable in near quantitative yield in soluble and in immobilized form. These techniques can optionally be performed in the milligram range, e.g., for the use of immunization and N-terminal protein sequencing, or in the analytical range.     

开管毛细管亲和液相色谱初探

 提出了一种新的亲和色谱模式开管毛细管亲和液相色谱。在内径为 5 0 μm的毛细管内表面键合一层三嗪染料配体 ,利用毛细管电泳仪的压力系统进行亲和色谱实验。采用流动相切换洗脱技术 ,牛血清白蛋白和溶菌酶获得了有效的分离。连续运行 10次 ,溶菌酶的出峰时间、峰面积和峰高的相对标准偏差分别为0 1% ,4 3% ,3 7%。在 8 6ng～ 2 8 7ng范围内 ,溶菌酶的进样量与峰面积和峰高都呈线性关系 ,其相关系数分别为 0 9946和 0 9988。     

溶胶-凝胶法固定胆固醇氧化酶偶联普鲁士蓝化学修饰电极的研究

用溶胶-凝胶法将胆固醇氧化酶固定在普鲁士蓝修饰的玻碳电极表面,制成了一种新型胆固醇传感器,实现了低电位下对胆固醇的间接测定,胆固醇的测定范围伏安法为5×10^-7～8×10^-5mol/L,安培法为5×10^-6～5×10^-4mol/L.伏安法检出限为1.2×10^-7mol/L,是目前所见灵敏度最高的胆固醇传感器之一,该传感器对胆固醇的测定可避免常规电化学传感器测定中由于样品中大量存在的易氧化物质所带来的干扰,该传感器的寿命长,使用次数在300次以上.     

Rapid and sensitive determination of protein by light-scattering technique with Eriochrome Blue Black R

Based on the interaction between Eriochrome Blue Black R (EBBR) and proteins, which causes a strong light-scattering signal with the maximum scattering peak located at 398 nm, a simple, rapid, sensitive and selective method is developed for the determination of proteins by the light-scattering technique using a common spectrofluoremeter. Under proper experimental conditions, the protein determination can be performed in the range of 0.1-25, 0.1-20 and 0.25-25 μg ml⁻¹ for bovine serum albumin (BSA), human serum albumin (HSA) and human immunoglobulin G (IgG), respectively. The detection limit, calculated as 3 times the S.D. of nine blank measurements, are 33 μg l⁻¹ for BSA, 25 μg l⁻¹ for HSA and 38 μg l⁻¹ for IgG. Moreover, there is no significant difference among the scattering signals yielded by HSA, IgG and BSA, and almost no interference of many amino acids and metal ions. The method has been satisfactorily applied to the direct determination of the total protein in human serum, saliva and urine samples. The results obtained from the studies on the binding characteristics of EBBR to BSA indicated that an electrostatic force existed in the binding system, and the binding constant (K) and the number of the binding sites (n) at 25 °C are 1.69×10⁵ l mol⁻¹ and 0.946, respectively.     

Electroanalytical Study of Prussian Blue Modified Glassy Carbon Paste Electrodes

Two types of glassy carbon (GC) powder (i.e., Sigradur K and Sigradur G) have been mixed with mineral oil to obtain glassy carbon paste electrodes (GCPE's). The electrochemical behavior of such electrodes at different percentages of glassy carbon has been evaluated with respect to the electrochemistry of ferricyanide as revealed with cyclic voltammetry and the best paste composition was chosen. GC was then modified with Prussian Blue (PB), mixed at different percentages with unmodified GC and with a fixed amount of mineral oil in order to obtain PB modified glassy carbon paste electrodes (PB‐GCPE's). PB‐GCPE's with different percentages of GC modified with PB (PB‐GC) were compared and the dependence on the amount of PB on their performances was evaluated by studying the parameters of cyclic voltammetry (i.e., current peak, ΔE_p, anodic and cathodic current ratio, charge density) and the amperometric response to H₂O₂. Data interpretation based on the GC surface area is presented. GCPE's with a selected amount of PB‐GC were then tested as H₂O₂ probes and all the analytical parameters together with the dependence on pH were evaluated. Some preliminary experiments with these electrodes assembled as glucose, lysine and lactate biosensors are also reported.