Concerted Asynchronous Hula‐Twist Photoisomerization in the S65T/H148D Mutant of Green Fluorescent Protein

Fluorescence emission of wild‐type green fluorescent protein (GFP) is lost in the S65T mutant, but partly recovered in the S65T/H148D double mutant. These experimental findings are rationalized by a combined quantum mechanics/molecular mechanics (QM/MM) study at the QM(CASPT2//CASSCF)/AMBER level. A barrierless excited‐state proton transfer, which is exclusively driven by the Asp148 residue introduced in the double mutant, is responsible for the ultrafast formation of the anionic fluorescent state, which can be deactivated through a concerted asynchronous hula‐twist photoisomerization. This causes the lower fluorescence quantum yield in S65T/H148D compared to wild‐type GFP. Hydrogen out‐of‐plane motion plays an important role in the deactivation of the S65T/H148D fluorescent state.     

Transfer of Aryl Halide to Alkyl Halide: Reductive Elimination of Alkylhalide from Alkylpalladium Halides Containing syn‐β‐Hydrogen Atoms

β‐Hydride abstraction is a well‐accepted elementary step for catalytic cycles in organometallic chemistry. It is usually anticipated that alkylpalladium halides containing syn‐β‐hydrogen atoms will undergo β‐hydride abstraction to afford the Heck‐type products. However, this study discloses that the above general knowledge is only conditionally correct. Our experimental results demonstrate that the reductive elimination of alkylhalides from alkylpalladium halides containing syn‐β‐hydrogen atoms may surpass the β‐hydride abstraction or even become exclusive in certain cases.     

Neo‐Fused Hexaphyrin: A Molecular Puzzle Containing an N‐Linked Pentaphyrin

The first neo‐confused hexaphyrin(1.1.1.1.1.0) was synthesized by oxidative ring closure of a hexapyrrane bearing two terminal “confused” pyrroles. The new compound displays a folded conformation with a short interpyrrolic C???N distance of 3.102 Å, and thus it readily underwent ring fusion to afford a neo‐fused hexaphyrin with an unprecedented 5,5,5,7‐tetracyclic ring structure. Furthermore, coordination of Cu^II triggered a ring opening/contracting reaction to afford a Cu^II complex of an N‐linked pentaphyrin derivative. The roles of reactive N? C bonds in the porphyrinoid macrocycles were demonstrated.     

Effect of temperature on the morphologies and electrochemical properties of polyaniline-gold fibrillar nanocomposites

The polyaniline-gold (PANI-AuNPs) fibrillar nanocomposites were prepared via a simple one-pot synthesis route in ethylene glycol (EG) medium. The morphology of PANI-AuNPs was characterized by transmission electron microscopy (TEM), and their electrochemical properties were studied by CV, TAF and EIS measurement using an electrochemical workstation. The results show that the morphology of nanocomposites can be controlled by changing the temperature. The diameter of PANI-AuNPs composite nanofiber reduce from about 80 to 30 nm, and the size of AuNP also reduce from about 20 to 4 nm, with the rise of synthesized temperature. When the synthesized temperature is 10°C, the distribution of AuNPs is the best, and the amount of AuNPs dispersed in PANI is the most, as well as the electrochemical performance of PANI-AuNPs is the most excellent.     

气相色谱法测定不同水质中的二氯乙酸和三氯乙酸

采用气相色谱法测定水中二氯乙酸和三氯乙酸的含量。并且检测了地表水、海水、污水处理厂进口和化工废水等不同水质实际样品。水样中加入氯化钠,经硫酸酸化,甲基叔丁基醚萃取后,以硫酸-甲醇(20+80)溶液作为衍生试剂,衍生温度为50℃时,气相色谱-电子捕获检测器测定。在优化分离条件下,分流比为5比1,二氯乙酸和三氯乙酸具有良好的分离效果。二氯乙酸、三氯乙酸的检出限分别为0.21,0.14μg·L-1,加标回收率在97.4%~105%之间,测定值的相对标准偏差(n=6)小于6%。     

有机锡4-(4-吡啶基甲基硫代)苯甲酸酯的合成、结构与生物活性研究(英文)

通过4-(4-吡啶基甲基硫代)苯甲酸与三苯基氧化锡以及三环己基氢氧化锡反应,合成了三苯基锡4-(4-吡啶基甲基硫代)苯甲酸酯(1)及三环己基锡4-(4-吡啶基甲基硫代)苯甲酸酯(2)。它们的结构通过红外,核磁以及X-射线单晶衍射分析得到确证。化合物1表现为一维链状结构,而化合物2通过分子间的O-H…O和O-H…N氢键形成二维网状结构。生物活性测试表明,这2个化合物具有较高的抗肿瘤活性。     

多组分烟用香精定量分析方法的研究进展

综述了近年来烟用香精、香料各组分化合物的定量分析方法的研究进展。面积归一化法、内标法、外标法和标准加入法等常用色谱定量分析方法主要用于烟用香精、香料中目标化合物或单个组分的测定;多标定量法、特征峰-内标定量法和多元校正法能深入剖析烟用香精复杂体系中各组分含量(引用文献48篇)。     

以3-硝基邻苯二甲酸根构建的环状双核Zn(Ⅱ),Cd(Ⅱ)配合物的合成及晶体结构(英文)

以3-硝基邻苯二甲酸和咪唑及2,2′-联吡啶为配体构筑了2种配合物[Zn2(npa)2(Im)4](1)和[Cd2(npa)2(2,2′-bipy)2(H2O)2]·2H2O(2)(npa2-=3-硝基邻苯二甲酸根,Im=咪唑,2,2′-bipy=2,2′-联吡啶)。用元素分析、红外光谱对其进行了表征,并用单晶X-射线衍射测定了配合物的晶体结构;测定了配合物1和2的热稳定性。2个配合物均为双核分子,具有M2C8O4十四元大环结构。配合物1的双核单元通过分子间氢键形成3D网络结构,配合物2的双核单元通过分子间氢键和π-π堆积形成2D层状结构。     

基于2-丙基-4,5-咪唑二甲酸的锰(Ⅱ)和铜(Ⅰ)配合物的合成、晶体结构及性质研究(英文)

采用水热法合成了2个化合物{[Cu2(Hpimdc)(4,4′-bpy)]·H2O}n(1)和[Mn3(pimdc)2·6H2O]n(2)(H3pimdc=2-丙基-4,5-咪唑二甲酸,4,4′-bpy=4,4′-联吡啶),并对2个化合物进行了红外、元素分析、晶体结构和热稳定性分析。晶体结构分析发现化合物1之中的H3pimdc和4,4′-bpy交替与铜(Ⅰ)配位形成一维链线性铜(Ⅰ)配合物。沿a轴和(100)面去观察,2个一维链分子通过游离水连接而形成1个"U"型拓扑结构。而化合物2通过2-丙基-4,5-咪唑二甲酸链与锰(Ⅱ)连接为三维的网状结构。沿b轴方向,三维结构中存在交替的左/右手螺旋状二维结构。