微量热法研究超氧化物歧化酶反应

用微量热法研究了以过氧化氢酶反应为氧产生体系、以邻苯三酚自氧化反应为底物产生体系的超氧化物歧化酶 (SOD)催化超氧阴离子歧化反应的热动力学 ,测得 2 98 1 5K和pH 8 0时SOD反应和邻苯三酚自氧化反应的摩尔反应焓分别为- 1 6 0 .1和 - 2 1 8kJ·mol-1,并建立了一种新的SOD活力测定方法———微量热测活法 .实验结果表明 ,SOD对邻苯三酚自氧化反应的动力学参数及反应机理没有影响 ,在无SOD存在和有SOD存在时该自氧化反应在限量氧气条件下均遵循二级反应动力学 (对邻苯三酚和氧气各为一级 ) ,2 98 1 5K和 pH 8 0时其二级速率常数分别为 1 2 5和 1 30L·mol-1·s-1,同时提出了SOD抑制邻苯三酚自氧化反应的可能机理 .     

基于羟自由基体系的流动注射-化学发光检测水中的焦性没食子酸

建立了在酸性条件下基于羟自由基(.OH)反应的流动注射-化学发光检测水中焦性没食子酸的新方法。羟自由基由Fe3 和过氧化氢在线混合产生。它能氧化罗丹明6G产生微弱的光,而焦性没食子酸能显著的增强这一反应。方法的检出限为2.7×10-7g/L;线性范围为8.0×10-7~1.0×10-4g/L;线性方程为ΔI=25.436C 21.822(C:μg/L,r=0.9996)。对2.0×10-6g/L的焦性没食子酸平行测定11次,其相对标准偏差为4.80%。该方法成功的应用于环境水中焦性没食子酸的检测,其回收率在91.1%~108.8%。并探讨了该反应可能的机理。     

以邻氨基酚为底物的伏安酶联免疫分析体系酶促反应的研究

辣根过氧化物酶 (HRP)催化H2 O2 氧化邻氨基酚的酶促反应与邻氨基酚的氧化产物的电极还原反应相偶合的伏安酶联免疫分析新体系具有很高的灵敏度 ,测定HRP的检出限为 6 .0× 1 0 -10 g/L ,线性范围为 1 .0× 1 0 -9～ 4.0× 1 0 -6g/L .制备出了HRP催化H2 O2 氧化邻氨基酚的产物纯品 ,并应用电化学分析、高效液相色谱、紫外 可见光谱、红外光谱、13 C核磁共振谱、1H核磁共振谱、质谱、元素分析等技术对体系酶促反应进行了深入的研究 .在所选择的酶促反应条件下 ,生成的产物为 3 氨基吩嗪 .提出了酶促反应及其产物的电极还原过程 .     

催化动力学分光光度法测定痕量钒(Ⅴ)

在醋酸介质中 ,以抗坏血酸作活化剂 ,痕量钒 (Ⅴ )对溴酸钾氧化邻苯三酚红褪色的指示反应有灵敏的催化作用。研究了该反应的最佳实验条件和动力学参数 ,建立了一种测定超痕量钒 (Ⅴ )的新方法 ,该法选择性强、操作简便、快速 ,其线性范围为 0 .8～ 4.0 μg/L钒 (Ⅴ ) ;检出限为 6.8× 1 0 -9g/L。方法用于生物样品中痕量钒 (Ⅴ )的测定 ,结果满意。     

荧光动力学法测定超氧化物歧化酶的活性

超氧化物歧化酶的活力可以反映机体清除氧自由基的能力,在抗衰老研究中经常需对其进行准确测定。邻苯三酚自氧化可产生强荧光的醌,超氧化物歧化酶通过清除该反应过程中产生的超氧阴离子自由基使醌减少,据此建立了测定超氧化物歧化酶活力的荧光动力学方法。探讨了缓冲液的浓度、pH值、邻苯三酚浓度和温度对测定的影响。在Tris-HAC缓冲液浓度为0.1mol/L、pH8.2、邻苯三酚浓度为0.385mmol/L、温度为25℃的最佳条件下,得到SOD的线性响应范围为0.31~1.58mg/L;血清样品测定的RSD为1.12%(n=5);加标回收率在94.3%~103.49%之间。本法与黄嘌呤-黄嘌呤氧化酶法的测定结果一致,可用于动物样品中超氧化物歧化酶活力的测定。     

邻苯三酚自氧化反应的动力学研究

利用单扫示波极谱法(并辅以紫外-可见光谱法)研究了邻苯三酚在pH7.20～9.10的Tris－HCl缓冲体系中自氧化反应的动力学.结果表明, 在过量溶解O₂存在时, 反应对邻苯三酚为一级.在一定pH范围内, 准一级反应表现速率常数K_app随pH值的增加而增加, 说明H₂PYR-比H₃PYR对溶解O₂具有更高的反应活性.探讨了邻苯三酚自氧化生成半醒自由基和活性氧的反应机理, 用速率方程解释了实验现象.并为酶活力测定和药物抗氧活性研究提供了一种新方法.     

阻抑-催化褪色动力学光度法测定食盐中的微量碘

在KH2PO4-K2HPO4介质中,微量碘(I-)对过氧化氢氧化碱性藏花红褪色反应有抑制作用,据此,建立了阻抑催化褪色动力学光度测定痕量碘的方法。该法的线性范围为0~40μg/L,检出限为1.6×10-8g/L。本法用于食盐中微量碘的测定,分析结果满意。     

萃取催化光度法间接测定痕量抗坏血酸

研究了在pH5.5的HAc NaAc缓冲溶液介质中,利用抗坏血酸活化Fe(Ⅲ)催化H2O2氧化邻氨基酚的显色反应,用萃取平衡控制反应时间和水相中邻氨基酚的浓度及反应程度,通过测量424nm下有机相的吸光度,建立了萃取催化光度法间接测定痕量抗坏血酸的新方法。方法的线性范围为0～50.0μg/L,检出限为6.7×10-7g/L。方法可用于维生素C片和西红柿中抗坏血酸的测定。并对反应机理进行了探讨。     

银纳米粒子表面等离子共振吸收-分光光度法测定废水中的邻苯三酚

基于改良银镜反应,利用银纳米粒子的表面等离子共振吸收提出了测定废水中邻苯三酚的分光光度法。室温条件下,在氢氧化钠和氨水混合溶液的碱性环境中,以吐温-20作为分散剂,邻苯三酚作为还原剂,还原银氨溶液,反应生成银纳米粒子,溶液由无色变为亮黄色,并在410nm处产生银纳米粒子表面等离子共振吸收峰。溶液的吸光度与邻苯三酚的浓度在3.96×10-7~2.38×10~(-5) mol·L~(-1)范围内呈线性关系,检出限(3σ)为2.97×10-7 mol·L~(-1),摩尔吸光率为5.483×104L·mol~(-1)·cm~(-1)。该方法应用于工业废水中邻苯三酚的测定,测定值与普通分光光度法的测定结果一致,相对标准偏差(n=5)小于5.0%,加标回收率在95.4%~104%之间。     

酶催化荧光法测定河流污水中的痕量Cu(Ⅱ)

基于Tris-HCl缓冲介质中,血红蛋白对H2O2氧化L-酪氨酸体系有强烈催化作用,而Cu(Ⅱ)对这一反应体系具有强烈抑制作用,据此建立了一种酶催化荧光法测定Cu(Ⅱ)的新方法。荧光强度的变化与Cu(Ⅱ)的浓度在2.7~530μg/L范围内呈线性关系,检出限为0.6μg/L;对270μg/L Cu(Ⅱ)溶液进行11次平行测定其相对标准偏差为3.60%。该方法已成功应用于河流污水中痕量Cu(Ⅱ)的测定。     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.