稳定直线型硝酮-O_2~(-·)加合物的构型因素解析

对生命体系中的氧自由基,Spin trapping-ESR方法是公认的特征分析手段[1].然而,对超氧阴离子自由基(O2-·)而言,其自由基加合物稳定性差.对此,人们通过改变硝酮的取代基团,设计出更为有效的O2-·捕获探针[2,3].另外,Zweier研究组[4,5]还应用密度泛函理论研究了影响五元环状硝酮     

稳定直线型硝酮-O2^-·加合物的构型因素解析

对生命体系中的氧自由基,Spintrapping．ESR方法是公认的特征分析手段．然而,对超氧阴离子自由基O2^-而言,其自由基加合物稳定性差．对此,人们通过改变硝酮的取代基团,设计出更为有效的O2^-捕获探针．另外,Zweier研究组还应用密度泛函理论研究了影响五元环状硝酮超氧稳定性的内在分子构型因素．我们曾合成出一系列功能性的直线型硝酮类自由基捕获探针.     

荧光自旋捕获探针的合成及ESR捕获研究

设计合成了具有荧光基团的新型硝酮类自由基捕获探针并对其结构进行了表征.自由基捕获实验结果表明,该探针能实现对超氧阴离子自由基与碳中心自由基的捕获.此外,该自由基捕获探针反应产物的荧光强度与被捕获自由基浓度之间存在相关性,有望建立依据荧光强度分析被捕获自由基浓度的新方法.     

稳定直线型硝酮加-O-·2 合物的构型因素解析

对生命体系中的氧自由基, Spin trapping-ESR方法是公认的特征分析手段[1].然而, 对超氧阴离子自由基(O-·2)而言, 其自由基加合物稳定性差.对此,人们通过改变硝酮的取代基团, 设计出更为有效的O-·2捕获探针[2,3].     

应用密度泛涵理论与NBT还原光谱法对PBN的胡椒基类似物性能的评价与预测

本文首先合成两个新型自由基捕获剂,α-胡椒基-丁基-硝酮（PiBN）与它的磷酰基类似物（PiPN）,并进行了分子结构鉴定。为了改进水相中评价超氧阴离子自由基捕获动力学的手段,本文首次建立并检验了由氯化硝基四氮唑蓝（NBT）介导的光谱分析新方法。再者,为简化上述捕获反应动力学的理论预测途径作者运用密度泛涵理论（DFT）中B3LYP/6-311+G(d,p)//B3LYP/6-31G(d)方法计算出新型硝酮的LUMO轨道能。进一步结合对超氧阴离子自由基加合物稳定构型的理论优化结果可知：引入磷酰基不但可稳定自由基超氧加合物分子,而且大大增加硝酮捕获超氧阴离子自由基的速度常数。     

光催化氧化还原体系中硝酮与芳香叔胺的自由基偶联反应

通过氮α-位碳自由基构造氮α-位碳-碳键是合成含氮有机化合物的重要方法. 近期, 利用可见光催化氧化芳香叔胺—氮α-位去质子化形成氮α-位碳自由基的原理发展了一系列新颖的自由基加成(偶联)反应, 成为氮α-位碳自由基化学发展的重要方向. 本文应用Ir-催化剂, 实现了光催化氧化还原体系中硝酮与芳香叔胺的自由基偶联反应, 高效地合成β-氨基羟胺化合物. 该反应条件温和、操作简单, 具有较高的原子经济性, 且对于各种链状、环状以及手性硝酮都具有良好的适用性, 产物可方便地转化为重要的邻二胺化合物.     

脂族酰基过氧化物分解动力学的研究X: 过氧化酰热分解反应的自旋捕获ESR研究

用亚硝基丁烷(TNB)、亚硝基苯和C-苯基-N-叔丁基硝酮作为自旋捕获剂来捕获和检出一些二酰基过氧化物类化合物分解时形成的短命烷基自由基. 报导了烷基自由基对自旋捕获剂加成的氮氧化物自由基的电子自旋共振谱, 并观察到2,4,4-三甲基戊基自由基中α-CH2的氢是非对映和非等价的. 据此, 认为与这一类自由基的加合物产生的电子自旋共振谱与其它类型自由基是不同的.     

硝基苯甲酸酯水解反应单电子转移机理的证据: ESR和自旋捕获的研究

对-硝基苯甲酸甲酯(1),对-硝基苯甲酸正丁酯(2),对-硝基苯甲酸叔丁酯(3),对-硝基苯甲酸苄酯(4),对-硝基苯甲酸苯酯(5),对-硝基苯甲酸(对-硝基)苯酯(6),间-硝基苯甲酸甲酯(7),间-硝基苯甲酸乙酯(8),间-硝基苯甲酸苯酯(9)和3,5-二硝基苯甲酸甲酯(10)与氢氧化钾在二甲亚砜中反应,反应产物分别为相应的对-硝基苯甲酸和间-硝基苯甲酸.反应液用 ESR 检测,得到1—10自由基负离子的 ESR 谱.用自旋捕获技术证明反应过程中有·OH 自由基生成.自由基捕获剂亚硝基叔丁烷(TNB),苯基叔丁基硝酮(PBN)和氧气使产物硝基苯甲酸的产率降低.结果表明,1—10与 KOH 在 DMSO 中反应存在单电子转移机理.     

硝基苯甲酸酯水解反应单电子转移机理的证据: ESR和自旋捕获的研究

对-硝基苯甲酸甲酯(1), 对-硝基苯甲酸正丁酯(2), 对-硝基苯甲酸叔丁酯(3), 对-硝基苯甲酸苄酯(4), 对-硝基苯甲酸苯酯(5), 对-硝基苯甲酸(对-硝基)苯酯(6), 间-硝基苯甲酸甲酯(7), 间-硝基苯甲酸乙酯(8), 间-硝基苯甲酸苯酯(9)和3,5-二硝基苯甲酸甲酯(10)与氢氧化钾在二甲亚砜中反应, 反应产物分别为相应的对-硝基苯甲酸和间-硝基苯甲酸。反应液用ESR检测, 得到1-10自由基负离子的ESR谱。用自旋捕获技术证明反应过程中有OH自由基生成, 自由基捕获剂亚硝基叔丁烷(TNB), 苯基叔丁基硝酮(PBN)和氧气使产物硝基苯甲酸的产率降低, 结果表明, 1-10与KOH与DMSO中反应存在单电子转移机理。     

基于脱单芳氨基反应的一氧化氮荧光探针的合成及其在活细胞中成像的应用

合成了基于脱单芳氨基反应的一氧化氮荧光探针(5-氨基荧光素)并对其进行了结构表征。研究发现合成的5-氨基荧光素作为荧光探针能选择性识别NO。探针的荧光强度与NOC18浓度(0~8.0×10-5mol/L)呈良好的线性关系,经1H NM R和H RM S实验证实了探针识别NO为脱氨基的机理,并在小鼠单核巨噬细胞白血病细胞(Raw 264.7)活细胞中实现了对NO的成像。     

基于糖和苯硼酸动态共价键的高效蛋白质表面修饰方法

糖和蛋白质的相互作用参与了很多重要的生命过程.研究糖和蛋白质的相互作用有多种手段,石英晶体微天平(QCM)是其中重要的一种.研究中常需要将蛋白质通过共价键连接在天平芯片的表面.但是,用于检测糖分子的蛋白质多为植物凝集素,它们的分子量大,表面可修饰位点少,通过共价键修饰在芯片表面的效率偏低.本文提出一种基于糖和苯硼酸之间动态共价键的新修饰方法,能够大幅度提高蛋白质在芯片表面的修饰效率.     

新型混价铜配合物[CuⅠCuⅡ(Ophen)2Cl]·H2O(HOphen=2-羟基-1,10-邻菲咯啉)的水热合成和晶体结构

报道了一种新型混价铜配合物[CuⅠCuⅡ(Ophen)2Cl]·H2O(HOphen=2-羟基-1,10′-邻菲咯啉)的水热合成和晶体结构.该化合物属于三斜晶系,P1空间群,a=0.91667(18)nm,b=1.0546(2)nm,c=1.1705(2)nm,α=80.50(3)°,β=80.56(3)°,γ=66.87(3)°,V=1.0202(3)nm3,Z=2,Dc=1.872Mg/m3,R1=0.0508,(wR2)=0.1481.标题化合物由一种新型的双核铜配合物和一个结晶水组成.邻菲咯啉在水热反应中发生羟基化,形成新型的羟基化邻菲咯啉.两个这样的配合物通过Cu…Cu间的范德华力相互作用形成二聚体.二聚体之间通过Ophen基团的π-π堆积以及C—H…Cl弱相互作用构筑成三维超分子网络.水分子处于网络的孔穴中.该化合物为邻菲咯啉的羟基化提供又一个新的范例.     

功能性咪唑基钒氧配合物的合成、结构与仿生催化

在室温条件下,甲醇体系中设计合成了一种新的以咪唑为配体的功能性钒氧配合物VO(imidazole)₄(SO₄)·H₂O(1)。 进行了元素分析、红外光谱表征,并用X-ray单晶衍射法测定了配合物1的晶体结构。 配合物1的晶体属于正交晶系,空间群:Pna2₁,a=1.384 4(3) nm,b=0.978 6(2) nm,c=1.361 7(3) nm,α=β=γ=90°,V=1.844 7(6) nm3,Z=4。 对配合物1的溴化催化活性进行了研究,通过实验得到了对苯酚红催化溴化的反应速率常数k=2.760 0×10⁷ L²/(mol²·s)。 讨论了配合物1的热稳定性,并结合从头计算结果进一步分析了配合物的稳定性及分子中配键的共价特征。 分析结果表明,V-O1的键序(1.055 3)明显要比V-O2(0.394 2)的键序大,V-N键序接近(0.333 6～0.341 9),配合物1的中心钒原子周围的价键类型均属于共价键范畴,键序分析结果与晶体结构测定的键长结果一致。     

THE USE OF BENZOPHENONE AS A PHOTOAFFINITY LABEL, LABELING IN p-BENZOYLPHENYLACETYL CHYMOTRYPSIN AT UNIT EFFICIENCY

Abstract— p -Benzoylphenylacetyl chymotrypsin, an acyl enzyme derivative containing the benzophenone group in the hydrophobic binding pocket, was prepared and is indefinitely stable at low pH. Photolysis of this covalent derivative leads to loss of enzymic activity and incorporation of the labeling group via formation of a second covalent bond. The efficiency of the photochemical processes is exceptionally high, producing 100% incorporation and at least 92% inactivation. Analysis of active site titration data for the photolyzed enzyme show that at least two different photochemical processes must be involved. Elimination of phosphorescence emission and reduction of UV absorption upon photolysis are consistent with initial hydrogen abstraction by benzophenone triplet state, followed by radical coupling, much as has been observed for the photoreaction of benzophenone with model systems. Photoaffinity labeling of chymotrypsin is also efficiently accomplished using two benzophenone derivatives which bind noncovalently to the enzyme's active site, although the rates of labeling are somewhat less than in the covalent complex.     

Crystal Structure,Vibrational Studies,Optical Properties and TG-DTA Investigations of a New Chlorocadmate Templated by 1-Methylimidazolium

Chemical preparation, X-ray single crystal diffraction, thermal analysis, electrochemical measurements, IR, Raman and UV spectroscopic investigations of a novel organic-inorganic hybrid material(C₄H₇N₂)CdCl₃(H₂O)(1) were described. 1-Methylimidazolium aquapentachlorocadmate(II) crystallized in the monoclinic system with P2₁/n space group. Its structure provided a new interesting example of infinite inorganic layers of [CdCl₃(H₂O)]_n^n- centered by (-101) planes. The [CdCl5(H₂O)]-anions were interconnected by O-H···Cl hydrogen bonds. Acidic protons of the chloride group were transferred to the organic molecule, giving the singly-protonated cations. The ability of ions to form a spontaneous three-dimensional structure through O-H···Cl and N-H···Cl hydrogen bonds was fully utilized. These hydrogen bonds induced notable vibrational effects. IR and Raman spectra were reported and discussed on the basis of group theoretical analysis and on quantum chemical density theory(DFT) calculation. The molecular HOMO-LUMO compositions and their respective energy gaps were also drawn to explain the activity of our compound. The role of the intermolecular interaction in this crystal was analyzed. The optical study was also investigated by UV-Vis absorption spectrum. Thermal analysis reveals the hydrous character of the compound. Cyclic voltammetry was studied to evaluate the spectral and structural changes accompanying electron transfer.     

Imine‐Linked Covalent Organic Framework on Surface for Biosensor

Imine‐linked covalent organic framework on amino functionalized silicon substrate was constructed via a step‐wise reaction between 1,3,5‐benzenetricarboxaldehyde and 1,4‐diaminobenzene. The obtained material was used as biosensor for bovine serum albumin (BSA) adsorption and probe DNA immobilization, which extended the application of covalent organic frameworks (COFs) to a new field.     

新型二维杂金属配位聚合物[La(Hida)Co(ida)2]·0.5H2O的水热合成与表征

采用水热法合成出一种新型二维杂金属配位聚合物[La(Hida)Co(ida)2].0.5H2O(ida=氨基二乙酸),并通过X射线单晶结构分析、红外光谱分析、元素分析、热重分析以及X射线粉末衍射分析对该化合物进行了表征.结构分析数据表明,该化合物属单斜晶系,C2/c空间群,晶胞参数a=0.97078(19)nm,b=2.4128(5)nm,c=0.85964(17)nm,β=114.91(3),°V=1.8263(6)nm3,Z=4,R=0.0126.该化合物是由一维La-Co杂金属链通过四齿羧酸配体连接形成的新型二维杂金属配位聚合物.     

An ethoxy intermediate in ethanol dehydration on Brønsted acid sites in zeolite

Acid-catalyzed ethanol dehydration on zeolite is shown to proceed via a covalent ethoxy group (C2H5O) as a stable intermediate, which was directly observed by IR spectroscopy.     

Sulfonated graphene oxide: the new and effective material for synthesis of polystyrene-based nanocomposites

The new sulfonated graphene oxide (S-GO) was prepared and firstly used as effective materials for the synthesis of polystyrene/graphene nanocomposites via Pickering emulsion polymerization. The functionalized, chemically modified GO nanosheets were obtained via facile covalent functionalization with a reactive surfactant, sulfanilic acid. It was found that Pickering emulsion could be formed by simple self-assembly method using the S-GO as a stabilizer (just need 1 wt% relative to the oil phase), which could be adsorbed at the oil–water interface to stabilize the emulsion effectively. After the Pickering emulsion polymerization of styrene, the polystyrene/S-GO nanocomposites were prepared successfully. It is noteworthy that the S-GO not only could be used as a highly effective surfactant for styrene monomers but also could be homogeneously dispersed and incorporated into the polymeric matrix.     

CUTANEOUS PHOTOTOXICITY OF TETRACYCLINE ANTIBIOTICS: GENERATION OF FREE RADICALS and SINGLET OXYGEN DURING PHOTOLYSIS AS MEASURED BY SPIN-TRAPPING and THE PHOSPHORESCENCE OF SINGLET MOLECULAR OXYGEN

Chlortetracycline (CTC) generated an aryl radical in aqueous buffer (pH 7.4) during near UV irradiation, as evidenced by the formation of 2-methyl-2-nitrosopropane spin adducts. The radical was produced via dechlorination, a photoprocess not previously reported for tetracyclines. Demeclocyc-line (DEM), another chlorinated tetracycline, did not produce detectable aryl radicals. Relative ¹O₂ yields obtained by direct luminescence measurements at 1268 nm for five tetracyclines in alkaline ethanol (demeclocycline · tetracycline · chlortetracycline · doxycycline · minocycline) showed that DEM produced approximately three times as much singlet oxygen as CTC. This constitutes direct evidence that tetracyclines sensitize both Type I and Type II photoreactions.