稀土及其配合物对蛇毒磷脂酶A_2活性的影响

分别研究了三价稀土离子 (La3 + ,Eu3 + ,Dy3 + ,Yb3 + )、二乙三胺五乙酸及其衍生物二乙三胺五乙酸 -双二甲酰胺 ,二乙三胺五乙酸 -双 (异烟肼 )与稀土离子的配合物以及Tb -谷氨酰胺配合物对蛇毒磷脂酶A2 活性的影响 .浓度低于 <3μmol/L的稀土离子可以激活磷脂酶A2 ,浓度大于 5 μmol/L后稀土离子对酶活性表现出抑制作用 ;外源Ca2 + 离子的加入可以缓解稀土离子对酶活性的抑制作用 ,表明稀土离子和钙离子是竞争性地结合在酶的活性部位 ;稀土离子和二乙三胺五乙酸及其衍生物的配合物对酶活性没有明显影响 ;Tb -谷氨酰胺在浓度大于 10 μmol/L后开始抑制酶的活性     

稀土离子和钙调蛋白对乳酸脱氢酶活性的影响

分别研究了三价稀土离子、稀土离子和钙调蛋白(CaM)的复合物以及作为稀土离子配体的二乙三胺五乙酸(DTPA)及其衍生物二乙三胺五乙酸-双二甲酰胺(DTPA-BDMA)和二乙三胺五乙酸-双(异烟肼)(DTPA-BIN)对乳酸脱氢酶(LDH)活性的影响.结果表明稀土离子浓度小于3μmol@L-1时对酶活性具有轻微的激活作用,离子浓度增大到6μmo1@L-1后则开始表现出抑制作用;钙调蛋白可以缓解这种抑制作用;二乙三胺五乙酸及其衍生物在浓度超过5μmol@L-1时对酶活性均有抑制,这种抑制作用在加入外源的钙调蛋白后也得到缓解.     

一种钙/钙调蛋白依赖性的蛇毒磷脂酶A2

稀土离子;活性;一种钙/钙调蛋白依赖性的蛇毒磷脂酶A2     

稀土离子对钙调蛋白与单克隆抗体分子识别的影响

分别采用酶联免疫吸附(ELISA)法和荧光标记技术比较了Ca²⁺,La³⁺,Eu³⁺和Yb³⁺离子对钙调蛋白与单克隆抗体2C3之间分子识别的影响.结果表明,金属离子与钙调蛋白作用后会诱导其发生不同的构象变化,并进一步影响到钙调蛋白与单克隆抗体2C3分子之间的结合强度.当钙调蛋白分别与La³⁺,Eu³⁺,Yb³⁺作用后,它与单抗2C3分子之间的解离常数为(26.8±2.5),(21.8±3.4)和(64.8±5.1)nmol/L,而结合Ca²⁺前后的钙调蛋白与单抗分子的解离常数分别为(177.2±2.8)和(157±4.2)nmol/L.这一结果表明,稀土离子诱导钙调蛋白发生的构象变化明显不同于钙离子的作用,这种差异可能是稀土与钙离子对钙调蛋白调控作用表现出差别的原因.     

稀土离子诱导钙调蛋白构象变化后的单克隆抗体制备

采用单克隆抗体技术研究了三价稀土离子与钙调蛋白作用后对其与靶分子识别能力的影响。牛脑钙调蛋白经2.4-二硝基氟苯修饰后再结合三价的铕离子,然后免疫Balb/c小鼠,经过3次免疫后在小鼠血清中检测到相应的抗体,抗体效价为1:12000;用杂交瘤细胞技术制备出一株抗钙调蛋白的单克隆抗体细胞株2C3;酶联免疫吸附法(ELISA)测定结果证实钙调蛋白结合稀土离子前后对该抗体的识别能力存在显着差异,表明该抗体可以用于进一步研究金属离子对钙调蛋白构象变化及其对靶分子识别的影响。     

稀土离子对钙调蛋白与蜂毒素作用的影响

分别用钙调蛋白和蜂毒素的内源荧光光谱以及铽离子的敏化荧光光谱考察了铽离子对钙调蛋白构象变化以及对钙调蛋白与蜂毒素相互作用的影响 .结果表明 ,铽离子首先结合在钙调蛋白的第Ⅰ和第Ⅱ位点 ,铽离子不影响钙调蛋白与蜂毒素的相互作用 ,蜂毒素与钙调蛋白作用后不影响铽离子在钙调蛋白上的键合顺序 .傅里叶变换红外光谱结果表明三价的镧离子与钙调蛋白作用使钙调蛋白的α螺旋结构增加 ,β折叠结构减少 ,与钙离子对它的二级结构影响相类似 .稀土离子在钙调蛋白 -蜂毒素复合体系中主要与钙调蛋白作用 .     

稀土离子(La3+, Gd3+, Yb3+)对线粒体产生活性氧的影响

研究了稀土离子对分离的线粒体产生活性氧(ROS)的影响. 采用荧光光度法跟踪线粒体内H2O2生成的动力学, 发现三种稀土离子(La3+, Gd3+, Yb3+)均能降低线粒体H2O2的生成; 用黄嘌呤-黄嘌呤氧化酶体系进一步证明稀土对超氧阴离子(·O-2)存在清除作用, 而对H2O2无清除作用; 测定了稀土对线粒体ROS代谢酶(谷胱甘肽过氧化物酶和超氧化物歧化酶)的活性影响. 结果表明, 三种稀土离子对线粒体谷胱甘肽过氧化物酶的活性基本没有影响, 而Gd3+和Yb3+稀土离子能明显抑制线粒体超氧化物歧化酶的活性.     

钙调蛋白Q41C/K75C突变体对Ca~(2+)和La~(3+)表现不同的结合模式

钙调蛋白(CaM)是一种多功能钙离子结合蛋白,作为对细胞内钙离子浓度变化的应答,它可以调节许多酶的活性.Q41C/K75C突变钙调蛋白(CaMSS)在N结构域端具有一个二硫键,此前研究表明,CaMSS对Ca2+亲合力明显降低.本研究结果发现,Ca2+和La3+与CaMSS的结合方式表现出了一种特殊的选择方式:Ca2+的结合位置为I,III和IV金属结合位点,而La3+与I,II和IV位点结合.综合文献和实验结果,我们提出一种结合机理的假设,即CaMSS的金属离子结合位点II(或III)可能通过长程效应,对另一端III(或II)的金属离子的结合发生响应,由于二硫键存在等原因,导致该位点丧失结合金属离子的合适蛋白构象.本研究结果为阐明金属离子与钙调蛋白结合的特异性机理提供了新的观点,也为以钙调蛋白为模版的蛋白设计提供了新思路.     

稀土Eu3+对不同光强下红叶石楠色素含量及PAL活性的影响

以盆栽红叶石楠(Photinia fraseri)优良品种'红罗宾'二年生组培苗植株为供试材料,探讨了不同遮光条件及稀土元素Eu3+处理对其顶部叶片色素含量、苯丙氨酸解氨酶(PAL)活性和Ca2+-ATPase酶活性的影响.结果显示,减少光照强度会导致叶绿素和类胡萝卜素含量上升,而使花青苷、红色素和PAL活性下降;稀土元素Eu3+处理一定程度提高了花青苷含量和PAL及Ca2+-ATPase酶活性.通过Eu3+和钙离子螯合剂(EGTA)、钙离子载体(A23187)、钙通道阻断剂(Verapamil)及钙调蛋白拮抗剂(CPZ)组合处理对50%光强下红叶石楠顶部叶片PAL活性影响的研究,推测Eu3+的生理作用机制可能是Eu3+通过细胞膜上的钙离子转运系统进入细胞内部,取代Ca2+-CaM信号系统中的Ca2+形成Eu3+ -CaM和(或)Eu3+-Ca2+-CaM复合物,替代Ca2+启动钙信号系统激活靶酶,调节效应酶功能,进而调控植物的一系列生理生化过程.     

La3+诱导钙调蛋白与鼠脑组织钙调蛋白亲合蛋白的结合

应用固定化钙调蛋白(CaM)亲合色谱法、变性丙烯酰胺电泳(SDS-PAGE)和基质辅助激光解析电离飞行时间质谱(MALDI-TOF-MS)等方法研究了La3+诱导CaM在大鼠脑匀浆液中的钙调蛋白亲合蛋白(CaMBP)谱以及CaM-CaMBP在模拟细胞环境下结合作用的La3+浓度依赖关系, 并与Ca2+的作用进行了比较. 实验结果表明, (1) La3+参与的CaMBP物种与Ca2+的基本相同. 鉴定了其中含量高且稳定出现的5种CaMBP分别是参与糖酵解反应的6-磷酸果糖激酶和3-磷酸甘油醛脱氢酶、细胞骨架类的微管蛋白和肌动蛋白以及应激反应相关的71000热休克同源蛋白, 表明稀土离子可能参与多种细胞过程; (2) La3+诱导CaM与5种CaMBP结合的浓度依赖曲线因CaMBP物种的不同而存在差别. 热休克同源蛋白、肌动蛋白或微管蛋白对La3+相对敏感, La3+在金属-CaM-CaMBP三元体系中与CaM的结合常数K与Ca2+的相近或稍高; 而6-磷酸果糖激酶和3-磷酸甘油醛脱氢酶体系对La3+的敏感性明显低于Ca2+. 其原因可能在于模拟细胞环境的复杂性以及CaM-CaMBP蛋白质相互作用对金属离子与CaM配位结合的调节.     

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%.     

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.     

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.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

Selective syntheses of 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones via temperature-dependent Rh(II)-carbenoid-mediated 2H-azirine-ring expansion

The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative.     

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.