石墨烯-金纳米材料修饰电极用于L-酪氨酸的检测

采用一种绿色简单的电化学方法将还原氧化石墨烯-金纳米复合薄膜共沉积到玻碳电极(GCE)上,作为传感器用于L-酪氨酸(L-Tyr)的检测.采用扫描电子显微镜(SEM)、循环伏安法(CV)和电化学阻抗谱(EIS)对修饰电极进行了表征.采用差分脉冲伏安法(DPV)研究了0.1 mol/L磷酸盐缓冲溶液中L-Tyr在修饰电极上的电化学行为,发现L-Tyr在修饰电极上的伏安响应比裸GCE明显提高.对复合薄膜的厚度、支撑电解质的p H值、沉积电位和积累时间进行了优化;在最佳实验条件下, L-Tyr的氧化峰电流在0.1~50μmol/L及50~1000μmol/L浓度范围内呈现良好的线性关系.该传感器的检出限为50 nmol/L,灵敏度为0.553μA·μmol·L^(-1),具有良好的重复性、稳定性和抗干扰性.

过量表达甲酸脱氢酶提高大肠杆菌合成L-2-氨基丁酸的效率

为了实现L-2-氨基丁酸(L-ABA)的高效生物合成,借助pACYCDuet-1和pET28a共表达系统,构建了携带L-苏氨酸脱氨酶(L-TD)、L-亮氨酸脱氢酶(L-L-DH)和不同活性甲酸脱氢酶(FDH)编码基因的重组大肠杆菌,分别命名为:E.coli BL21(DE3)/pACYCDuet-1-Ec TD-Es LeuDH:pET28a-Cb FDH和E.coli BL21(DE3)/p ACYCDuet-1-Ec TD-Es Leu DH:p ET28a-Cb FDH^(M)。经诱导表达后,L-苏氨酸脱氨酶和L-亮氨酸脱氢酶在两个重组大肠杆菌中的表达水平基本一致,而后者的甲酸脱氢酶酶活表达水平为(342.00±9.40)IU/mL,显著高于前者的(196.00±6.20)IU/mL。在50 mL反应体系中,200 mmol/L L-苏氨酸经220 r/min、30℃下反应6 h时,前者L-ABA得率为71%,后者为85%。结果表明,提高甲酸脱氢酶的表达水平可以显著提高L-ABA的合成效率。此外,优化反应温度后,在35℃下反应6 h时,L-ABA的得率可达90%。

Redox behavior of gold supported on ceria and ceria-zirconia based catalysts

A series of gold-based catalysts were prepared by deposition precipitation or incipient wetness impregnation on CexZ1-xO2 solid solutions （0.28≤x≤1.00）. The morphological and structural characterization of these catalysts were carried out with X-ray diffraction, trans- mission electron microscopy （TEM） analysis and physical adsorption technique, and their redox properties were studied by temperature programmed reduction using both H2 and CO as probe molecules. Two cycles of oxidation/reduction were carried out in order to evaluate the effects of redox aging and gold sintering on the oxygen exchange capability. As observed with other noble metals, gold enhanced and promoted the ceria reduction at lower temperatures. Reduction by CO was shown to be dependent on the fine dispersion of gold and to be nega- tively affected by the ageing process more than reduction with hydrogen. This might have implications in reactions like water gas shift and CO-PROX which involve CO as a main reactant.

Promoter effect of La2O3 on gold catalyst with different textural structures

Silica supported gold nanoparticles were synthesized and promoted by lanthanum oxide as dopant. The influences of LaOand silica textural structure on the gold dispersion, formation of active species, crystalline composition and the reacting role of dopants were studied in detail. The characterization results suggested that the dispersion of gold nanoparticles depended on the textural structure of silica without lanthanum oxide doping where small mesopores are more preferable to disperse gold nanoparticles. The addition of lanthanum oxide largely increased the dispersion of gold nanoparticles and oxygen active sites independent of the textural structure of silica support. The interaction between lanthanum oxide and silica enhanced by the synergy facilitated the release of oxygen vacancies and transition of active oxygen species. In addition, the chemical properties were greatly changed after lanthanum oxide addition which was only inconspicuously impacted by the initial textural structure of silica supports, shedding light on the further design of economic gold catalyst based on simple synthesis method.

Gold Nanozymes:From Concept to Biomedical Applications

In recent years,gold nanoparticles have demonstrated excellent enzyme-mimicking activities which resemble those of peroxidase,oxidase,catalase,superoxide dismutase or reductase.This,merged with their ease of synthesis,tunability,biocompatibility and low cost,makes them excellent candidates when compared with biological enzymes for applications in biomedicine or biochemical analyses.Herein,over 200 research papers have been systematically reviewed to present the recent progress on the fundamentals of gold nanozymes and their potential applications.The review reveals that the morphology and surface chemistry of the nanoparticles play an important role in their catalytic properties,as well as external parameters such as pH or temperature.Yet,real applications often require specific biorecognition elements to be immobilized onto the nanozymes,leading to unexpected positive or negative effects on their activity.Thus,rational design of efficient nanozymes remains a challenge of paramount importance.Different implementation paths have already been explored,including the application of peroxidase-like nanozymes for the development of clinical diagnostics or the regulation of oxidative stress within cells via their catalase and superoxide dismutase activities.The review also indicates that it is essential to understand how external parameters may boost or inhibit each of these activities,as more than one of them could coexist.Likewise,further toxicity studies are required to ensure the applicability of gold nanozymes in vivo.Current challenges and future prospects of gold nanozymes are discussed in this review,whose significance can be anticipated in a diverse range of fields beyond biomedicine,such as food safety,environmental analyses or the chemical industry.

PREPARATION OF POLYMER MICROSPHERES WITH PYRIDYL GROUP AND THEIR STABILIZED GOLD METALLIC COLLOIDS

Narrow disperse poly（ethyleneglycol dimethacrylate-co-4-vinylpyridine） （poly（EGDMA-co-4-VPy）） microspheres were prepared by distillation-precipitation copolymerization of ethyleneglycol dimethacrylate （EGDMA） and 4-vinylpyridine （4-VPy） with 2,2＇-azobisisobutyronitrile （AIBN） as initiator in neat acetonitrile. The polymer microspheres containing pyridyl group were then utilized as stabilizer for gold metallic colloids with the diameter around 7 nm, which were prepared by the in situ reduction of gold chloride trihydrate with sodium borohydride through the coordination of the pyridyl group on the gel layer and surface of the microsphere with the gold metallic nano-particles. The catalytic properties of the pyridyl- functionalized microsphere-stabilized gold metallic colloids and the behavior of the stabilized-catalyst for the recycling were investigated with reduction of 4-nitrophenol to 4-aminophenol as a model reaction.

Enhanced photo-catalytic activity of gold ion and gold modified

The gold ion modified TiO2 was prepared by means of sol-gel whereas gold deposited TiO2 was prepared by means of photoreduction. The physical properties were influenced significantly by the presence of gold ion or gold. The enhanced photo-activity of gold modified TiO2 vas quantified in terms of methylene blue degradation. The presence of gold ion in TiO2 lattices or gold on TiO2 surface enhanced their-photo-activity. The optimum molar content of gold ion doping and gold deposition all was 0.5%. The first-order rates constants of gold modified TiO2 was more than that of pure TiO2, and decreased by increasing the content of gold ion and gold when their contents were more than 0.5%. Gold ion doped in TiO2 lattices was more effective to enhance the photo-activity than gold on TiO2 surface. Moreover, the relationship between physical properties, chemical properties and photo-activity has been discussed.

Richard L. Abbott,MD,to Receive Duke Elder International Gold Medal at the WOC2014

27 January 2014San Francisco,CA,USA-The International Council of Ophthalmology(ICO)Board of Trustees is pleased to announce the selection of Richard L.Abbott,MD,as the 2014 International Duke Elder medalist.The Duke Elder Medal is awarded every four years to an ophthalmologist who,by his/her distinction,leadership,and teaching,has contributed most to the development of international relations and friendship between ophthalmologists,and who has advanced the field by his/her contributions in writing and organization in ophthalmology.

Gold Nanoparticles of Multiple Shapes Synthesized in L-Tryptophan Aqueous Solution

In this paper, we describe a simple and efficient synthesis of gold nanoparticles(GNPs) of various shapes(spherical, rod-like, hexagonal, truncated triangular, and triangular) using Au(Ⅲ) reduction in aqueous solutions by L-tryptophan. We evaluated the influences of reaction temperature, foreign metal ions Ag(Ⅰ), and surfactants of nonionic(polyethylene glycol, PEG), anionic(sodium dodecyl sulfate, SDS), and cationic(cetyltrimethyl ammonium bromide, CTAB) on GNPs synthesis. We characterized the resultant GNPs using UV–visible adsorption spectroscopy, transmission electron microscopy/high-resolution transmission electron microscopy, scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, selected-area electron diffraction, and Fourier-transform infrared spectroscopy. We fabricated the variously sized GNPs by controlling the rate of the reduction of gold ions in aqueous solution by varying the reaction temperature: the higher the temperature, the smaller the gold nanospheres. We found the existence of Ag(Ⅰ) to reinforce the reduction of Au(Ⅲ) and to correspond with the appearance of some amorphous bimetallic Au/Ag nanoparticles. Additionally, we found the presence of surfactants to greatly influence the shape of the formed GNPs, especially the presence of CTAB, which results in the anisotropic growth of gold nanocrystals into hexagonal, truncated triangular, and triangular nanoplates. In addition, with the increase in CTAB concentration, we found the amount of gold nanoplates to first increase and then decrease. Finally, we performed preliminary explorations of the reduction process and morphological evolution to propose possible corresponding reduction and morphological evolution pathways.

Morphological Control of Gold Nanoparticles by Green Synthesis Using L-Tryptophan and Other Additives

This study focuses on shape-controlled synthesis of gold nanoparticles, using the green reducing agent L-Tryptophan(L-Trp), which is non-toxic and eco-friendly. This specific agent was investigated to realize certain morphology controlling effects by changing the relative growth rates among various crystal planes. Experimental samples were characterized by transmission electron microscope, UV-Vis spectrophotometer and X-ray diffraction(XRD) for size and morphological information. The effects of the specific additives of PVP((C_6 H_9 NO)_n), CTAB(C_(16)H_(33)(CH_3)_3 NBr), and KBr were examined for their morphological control individually and synergistically in this system. Hexagonal gold nanoparticles were successfully obtained via the PVP/CTAB and PVP/KBr systems. Particular amounts of PVP/KBr produced various polyhedron structures, such as cubes, and others with triangular and rhombic straight-side cross sections.

多酶体系中谷胱甘肽HPLC分析方法研究

为了建立一种快速有效的方法来满足体外酶催化法生产谷胱甘肽中各复杂成分的定性及定量检测。依据反应液各组分的性质与特性,利用HPLC研究建立了一种新的分离方法。结果表明,通过此方法可实现L-半胱氨酸、L-谷氨酸钠、ATP、AMP、ADP、还原型谷胱甘肽、氧化型谷胱甘肽各组分的分离,分离度均>1.5,L-半胱氨酸与甘氨酸分离度>1.2;底物及产物曲线线性为R^(2)>0.99,回收率为94.6%~110.0%,连续检测6次RSD均<2.0%;且单个样品检测时间为15 min,与药典片剂检测方法45 min相比,缩短了检测时间,可快速出具检测结果,更有利于日常分析检测。

基于壳聚糖-纳米金/纳米普鲁士蓝/L-半胱氨酸修饰的葡萄糖传感器的研究

在金电极表面修饰带正电荷的L-半胱氨酸,再利用静电吸附作用固定纳米普鲁士蓝(nano-PB),然后利用壳聚糖-纳米金复合膜将葡萄糖氧化酶(GOD)固定于修饰电极表面,制成新型的葡萄糖传感器.通过交流阻抗技术,循环伏安法和计时电流法考察了电极的电化学特性.在优化的实验条件下,该传感器在葡萄糖浓度为3.0×10-6～1.0×10-3mol/L范围内有线性响应,检测下限为1.6×10-6mol/L.此外该传感器具有响应快、稳定性好和选择性良好的特点,能有效排除常见干扰物质如抗坏血酸、尿酸等对测定的影响.

L-半胱氨酸修饰金电极测定水中铜离子的研究

通过共价自组装的方法制得了L 半胱氨酸单分子层修饰金电极 ,以该修饰电极为工作电极 ,建立了一种灵敏的、选择性的检测水中痕量铜离子的新方法 .在富含铜离子的磷酸缓冲液中搅拌富集 ,铜离子与修饰电极表面的L 半胱氨酸形成电活性配合物吸附在电极表面 .用该电极对不同浓度的铜离子进行电化学检测时发现仅仅是峰电流发生改变 ,而峰电位不变 .峰电流随铜离子浓度的增大而增大 ,在 0 .1～ 30 μmol/L之间出现良好的线性关系 .其最低检测限可达 5nmol/L 。

L-半胱氨酸自组装膜修饰金电极对抗坏血酸的电催化作用及其测定

金电极表面对L 半胱氨酸 (L Cys)有特性吸附 ,而L Cys分子在等电点pH附近因静电引力和氢键作用形成分子对 ,从而在电极表面自组装形成L Cys双层膜。L Cys修饰金电极对抗坏血酸 (AA)具有良好的电催化作用。用示差脉冲伏安法对AA进行了测定 ,氧化电流与AA的浓度在 1.0× 10 -3 ～ 4× 10 -6mol/L范围内呈良好的线性关系 ,线性相关系数为 0 .9981;检出限为 4× 10 -7mol/L。用于药片中AA含量的测定 ,结果令人满意。

L-抗坏血酸没食子酸酯的酶催化合成及抗氧化性

以没食子酸和L-抗坏血酸为原料,在固定化脂肪酶Novozym 435催化下合成了L-抗坏血酸没食子酸酯,并测试了其抗氧化活性。结果表明,在没食子酸10 mmol,L-抗坏血酸20 mmol,脂肪酶0.25 g,环己酮20 mL,50℃反应24 h的条件下,没食子酸转化率达82.7%。抗氧化性试验表明,L-抗坏血酸没食子酸酯可以有效清除DPPH自由基和羟基自由基,其IC50分别为9.97μmol/L和2.45 mmol/L,而L-抗坏血酸清除DPPH自由基和羟基自由基的IC50分别为23.55μmol/L和5.14 mmol/L,抗氧化活性明显好于L-抗坏血酸。

对乙酰氨基酚在多壁碳纳米管L-半胱氨酸共组装修饰金电极上的电化学行为研究及其测定

在N，N-二环已基碳酰亚胺（DCC）存在介质下，通过酰氨键使羧基化的多壁碳纳米管（MCNTs）与L-半胱氨酸（L-Cys）缩合，功能化的MCNTs通过S-Au键自组装（SAMs）到金电极表面，制备了修饰电极（MCNTs-L-Cys-Au／SAMs-CME），并对电极的表面结构进行电化学表征。研究表明，该修饰电极对对乙酰氨基酚的电化学氧化具有明显的催化作用。同时，对其催化氧化的机理进行了初步探讨。将此修饰电极用于流动注射不可逆双安培（FI-IB）体系的构建，即利用对乙酰氨基酚在MCNTs-L-Cys-Au／SAMs-CME上的氧化和KMnO4在另一支铂电极上的还原构建了双安培检测体系，成功的建立了在外加电压为0V条件下流动注射双安培法直接测定对乙酰氨基酚的新方法。在0V外加电压下，在0．05mol／L硫酸载液中，该氧化峰峰电流与对乙酰氨基酚浓度在2.0×10^-6～2．0×10^-4mol／L范围内呈良好的线性关系，其线性回归方程为i（nA）=8．21×10^7C＋200（r=0．9984，n=9）；在2．0×10^-4～1．0×10^-3mol／L范围内呈线性关系，其线性回归方程为i（nA）=2．30×10^7C＋10^4（r=0．9938，n=4），方法检出限为1．0×10^-6 mol／L（S／N=3）；连续测定1．00×10^-4mol／L对乙酰氨基酚标准溶液20次，电流值RSD为2．7％，进样频率为90样／h。该方法具有较高的选择性和灵敏度。对乙酰氨基酚片中的对乙酰氨基酚的含量的测定，结果比较满意。

硼酸催化合成L-(+)-酒石酸二乙酯

以四氯化碳为溶剂,L-酒石酸与无水乙醇为原料,在硼酸的催化下,合成了L-(+)-酒石酸二乙酯,其结构经IR确证,比旋光度经旋光仪测定。试验得最佳反应条件:n(L-酒石酸)∶n(乙醇)为1∶5;四氯化碳为30 mL;反应温度为70℃;硼酸用量为2 g条件下,酯化率达到96.73%,收率达到90.07%。。

L-半胱氨酸自组装修饰金电极-不可逆双安培测定阿魏酸

在裸金电极上制备了L-半胱氨酸自组装膜金修饰电极（L-Cys／SAM—Au／CME），将自组装膜修饰电极用于不可逆双安培体系，利用阿魏酸在L—Cys／SAM—Au／CME上的氧化和KMnO4在裸金电极上的还原，构建双安培检测新体系，建立了在外加电压为0V条件下，流动注射双安培法直接测定阿魏酸的新方法。在0．05mol／LH2SO4溶液中，该氧化峰峰电流与阿魏酸浓度在5．0×10^-7-8．0×10^-5mol／L范围内呈线性关系（r=0．9961，n=10），其线性回归方程为i（nA）=4．16×10^7C＋50，在1．0×10^-4 -1．0×10^-3mol／L范围内呈线性关系（r=0．9955，n=5），其线性回归方程为i（nA）=5．6×10^6C＋300，检出限为1．2×10^-7mol／L。连续测定2．0×10^-5mol／L阿魏酸溶液25次，电流值RSD为1．20％，进样频率为80样／h。该方法具有较宽的线性范围、较高的选择性和灵敏度，样品处理方法简单快速，适于在线分析。对阿魏酸钠盐注射液中阿魏酸的测定结果满意。

聚L-精氨酸/纳米金修饰电极测定多巴胺

利用多电位脉冲沉积法制备纳米金修饰电极（AuNPs／GCE），再将L-精氨酸电聚合在AuNPs／GCE表面，制备出一种新型的聚L-精氨酸／AuNPs／GCE。采用原子力显微镜对上述电极进行了表征，并研究了多巴胺在其上的电化学行为。结果表明：在pH5．7的磷酸盐缓冲溶液中，聚L-精氨酸／AuNPs／GCE对多巴胺的氧化有良好的电催化作用，多巴胺的氧化还原反应是受吸附控制的准可逆过程。多巴胺的浓度在8．0×101～1．0×10-4m01．L叫范围内与其氧化峰电流呈线性关系，检出限（3S／N）为1．0×10-7mol．L-1。加标回收率在96．5％～104％之间。对3．0×10-5mol·L-1。多巴胺溶液连续测定7次，峰电流的相对标准偏差为2．6％。

L-半胱胺尾式卟啉铜(II)修饰金电极检测苯酚

将制备的L-半胱胺卟啉铜(II)(CuL)配合物自组装在Au电极表面,获得电化学苯酚传感器(CuL/Au)。在pH 7.0的磷酸盐缓冲液(PBS)中于-0.4 V^0.5 V(vs.SCE)电位范围内有一对氧化还原峰,峰电位分别为Epa=0.09 V和Epc=-0.06 V。实验结果表明CuL能够催化氧化苯酚,通过产物在电位0.1 V下的电化学响应对苯酚进行测定。该电极对苯酚表现出快速的响应(响应时间<10 s)。传感器对苯酚的测定具有较宽的线性范围(5.0×10-7mol.L-1~2.5×10-4mol.L-1),检出限为2.0×10-7mol.L-1。该电极用于地表水中苯酚含量检测,并与标准方法4-氨基安替比林分光光度法作了对照,结果满意。