单宁酸与牛血红蛋白相互作用的光谱研究

利用荧光光谱技术研究了单宁酸与牛血红蛋白分子的相互作用。实验结果表明:单宁酸分子与BHb发生反应生成基态复合物,导致BHb内源荧光的猝灭,该猝灭属于静态猝灭。测定了不同温度下该反应的表观结合常数、结合位点数及结合热力学参数,热力学参数的变化表明上述作用过程是一个熵增加、自由能降低的自发分子间作用过程,单宁酸与BHb之间以疏水和氢键作用力为主;根据Frster能量转移理论,测得供体与受体间结合距离r和能量转移效率E;并用同步荧光光谱法探讨了单宁酸对BHb构象的影响。     

光谱-分子模拟法分析杨梅素与人血清白蛋白的分子作用机制

在模拟生理条件下,用多种光谱法结合分子对接法测定了杨梅素(MY)与人血清白蛋白(HSA)的相互作用.研究结果表明,MY能够明显猝灭HSA的荧光,MY与HSA的相互作用为复合式静态结合过程,结合强度较强.热力学和分子对接结果表明,MY与HSA是自发结合的,维持MY与HSA的相互作用力主要是氢键和范德华力.能量转移结果表明...     

光谱和分子模拟法研究乙硫异烟胺与木瓜蛋白酶的分子作用机制

利用荧光光谱、紫外光谱和分子模拟方法研究了乙硫异烟胺(TH1314)与木瓜蛋白酶之间的相互作用, 求得了不同温度下的结合常数K. 研究结果表明, 静态猝灭是导致乙硫异烟胺对木瓜蛋白酶荧光猝灭的主要原因. 通过计算热力学参数, 可知乙硫异烟胺与木瓜蛋白酶相互作用的吉布斯自由能表现为较大的负值, 并结合作用过程的焓变和熵变推断出乙硫异烟胺与木瓜蛋白酶之间的作用力是以疏水和氢键作用为主. 同时, 利用紫外光谱和同步荧光光谱定性讨论了乙硫异烟胺对木瓜蛋白酶构象的影响. 分子模拟研究表明, 乙硫异烟胺与木瓜蛋白酶的相互作用不仅存在疏水作用, 而且有氢键作用, 这与光谱及热力学研究结果是一致的.     

坦索罗辛与β-环糊精相互作用的光度法和分子模拟研究

在模拟生理条件下,采用光度法和分子模拟技术研究了坦索罗辛与β-环糊精(β-CD)的相互作用。由实验所得的热力学参数ΔH<0,ΔG<0,说明坦索罗辛与β-CD发生了一个放热、自发的结合过程;由ΔH<0且ΔS<0推断二者主要靠氢键和范德华力发生作用。采用分子模拟技术对其相互作用从分子水平上进行预测,其结果与实验结果基本一致。     

分子光谱法研究铝酞菁与牛血红蛋白的相互作用

利用紫外可见吸收光谱和荧光光谱研究了在生理pH条件下铝酞菁与牛血红蛋白(BHb)的相互作用.实验结果表明:铝酞菁分子与BHb发生反应生成基态复合物,导致BHb内源荧光的猝灭,该猝灭属于静态猝灭.测定了不同温度下该反应的表观结合常数、结合位点数及结合热力学参数,热力学参数的变化表明铝酞菁与BHb之间以静电和疏水作用力为主;根据Frster能量转移理论,测得供体与受体间结合距离r和能量转移效率E;并用同步荧光光谱法探讨了铝酞菁对BHb构象的影响.     

桔皮苷与牛血清白蛋白相互作用的研究

运用荧光光谱、紫外光谱法研究了桔皮苷与牛血清白蛋白(BSA)的相互作用。桔皮苷分子与BSA作用导致BSA内源荧光猝灭,猝灭机理主要为静态猝灭,并存在非辐射能量转移。测定了不同温度下该反应的结合常数、结合位点数及结合热力学参数。结果表明:桔皮苷与BSA之间主要为氢键或范德华作用力,作用过程是一个熵增加、自由能降低的自发分子间作用过程;测得了供体与受体间结合距离r和能量转移效率E;并用同步荧光技术考察了桔皮苷对BSA构象的影响。     

荧光法研究氧氟沙星与牛乳铁蛋白的相互结合作用

用荧光光谱法研究了稀水溶液中牛乳铁蛋白与氧氟沙星分子之间的结合作用机制.以荧光猝灭法测定了该反应的结合常数K, 结合位点数n；并依据Förster偶极-偶极无辐射能量转移机制,得到氧氟沙星和牛乳铁蛋白色氨酸残基之间结合距离r和能量转移效率E；并用同步荧光技术考察了氧氟沙星对牛乳铁蛋白构象的影响；牛乳铁蛋白与氧氟沙星分子之间有较强的结合作用,而且氧氟沙星对牛乳铁蛋白的构象有一定的影响.     

光谱法及分子对接研究邻苯二甲酸单乙基己基酯与人血清白蛋白的相互作用

通过荧光光谱法、紫外分光光度法以及分子对接技术探究邻苯二甲酸单乙基己基酯(MEHP)与人血清白蛋白(HSA)之间的相互作用及其作用机制。光谱学数据显示,MEHP诱导HSA内源荧光猝灭是因为两者间发生非辐射能量转移并形成稳定的复合物;不同温度下的热力学常数表明范德华力或氢键为MEHP与HSA结合的主要驱动力;三维荧光光谱结果证实MEHP改变了HSA的构象;同步荧光光谱和位点实验表明,MEHP在位点Ⅰ与HSA结合。根据光谱学的研究结果,采用分子对接技术模拟MEHP与HSA在分子水平上的相互作用机制,结果与光谱学研究结果一致。     

叶酸与氨基酸相互作用的荧光光谱

在模拟动物生理条件下,利用荧光光谱法在分子水平上研究了叶酸同色氨酸、酪氨酸、苯丙氨酸的相互作用;根据双对数方程求出了不同温度下两者反应的结合常数和结合位点数.结果表明:叶酸能导致氨基酸的荧光猝灭,三种氨基酸的猝灭机制均为静态猝灭;从相应的热力学参数可知,色氨酸和酪氨酸与叶酸之间的主要作用力为疏水作用力,而苯丙氨酸与叶酸之间的主要作用力为氢键和范德华力.     

桑色素与血清白蛋白相互作用热力学行为

利用荧光光谱、紫外-可见吸收光谱、圆二色谱、分子模拟等方法,在近似生理条件下,以牛血清白蛋白(BSA)为模式蛋白质,研究了桑色素(Morin)和血清白蛋白相互作用的热力学行为及其特征。荧光光谱结果表明:Morin能有效猝灭BSA的内源荧光,猝灭机制为静态猝灭;通过van’t Hoff方程,获取了BSA与Morin结合的热力学参数(?H?、?S?、?G?等),发现Morin与BSA两者之间的相互作用是一个吉布斯自由能降低的自发过程,且氢键和范德华力是二者结合的驱动力。通过分子模拟方法,发现Morin结合在BSA分子亚结构域IIIA的疏水腔内位点II,荧光共振能量转移结果表明Morin和与BSA的两个色氨酸残基的平均距离为3.09nm。圆二色谱结果表明Morin分子的结合会引起BSA分子α-螺旋含量降低。     

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.