AT1受体的中药活性成分筛选模型及其作用机理研究

传统中药对治疗心血管类疾病疗效显著,例如钩藤、黄芪、益母草等在临床应用广泛.现代药理研究表明钩藤碱可以降压;黄芪中毛蕊异黄酮能舒张血管平滑肌、保护心脑血管;益母草碱可扩张微血管,改善血液流变异常,但它们分子层面作用机制尚不明确.首先以牛视紫红质蛋白为模板,模建出心血管疾病主要靶点AT1受体的三维结构.然后将AT1受体拮抗剂和中药活性成分与受体模型结合的作用方式进行了对比研究,据此提出了中药活性成分治疗心血管疾病的作用机理,并建立了AT1受体的中药活性成分筛选模型.结果表明:黄芪毛蕊异黄酮等中药活性成分能与AT1受体活性口袋中的残基发生氢键作用,结合方式与AT1受体拮抗剂相似.每一种AT1受体拮抗剂均与His183,Lys199,His256,Gln257,Ser105,Ser109,Tyr113,Asn200中多个发生氢键作用;黄芪毛蕊异黄酮与Try113,Lys199,Gln257,Ser105发生氢键作用.本研究从分子层面上阐释了一些中药活性小分子的治病机理,为进一步挖掘中药资源,研究AT1受体相关的心脑血管类药物,合理设计和筛选AT1受体的拮抗剂提供重要依据.     

新型减肥药利莫纳班的离子阱质谱和电子轰击质谱研究

新型减肥药利莫纳班(rimonabant)是一种选择性CB1受体拮抗剂,服后不易反弹.利莫纳班具有减轻体重和戒除烟瘾的功效,并能降低胆固醇、预防肥胖人群患上心脏病和糖尿病等.     

基于结构和药效团特征的人类腺苷受体拮抗剂选择性比较

腺苷受体是重要的治疗靶标,选择性腺苷受体拮抗剂具有广泛的临床应用前景.本文通过同源模建构建了腺苷A₁、A_2B和A₃受体的结构,采用LigandScout 3.12软件分别构建了腺苷受体四种亚型的拮抗剂药效团模型.然后利用Schrödinger程序中的Induced Fit Docking模块完成受体-拮抗剂结合模式的预测,并与药效团结果进行比对.结果发现,由于结合口袋部位的残基在家族间高度保守,模建得到的各个亚型受体的初始结构活性口袋部位极为相似,无法用于亚型选择性拮抗剂的识别.而腺苷受体四种亚型拮抗剂药效团的药效特征与空间排布都不同,并与以前突变实验信息相吻合.研究结果说明,结合口袋部位的优化是模建中的关键步骤,基于配体的药效团模型所包含的一系列药效特征元素如氢键受体、氢键供体、疏水基团、芳环中心,可以很好地表征受体结合部位氢键、疏水空腔的位置及其方向.本文研究结果可以为进一步的优化同源模建结果,寻找新型的人类腺苷受体选择性拮抗剂提供理论依据.     

神经介素B受体与拮抗剂、激动剂的分子模拟研究

大鼠神经介素B受体(rat neuromedin B receptor, rNMBR)属于G蛋白偶联受体(G-protein coupled receptor, GPCR) A家族的成员. GPCR的结构特征和在信号传导中的重要作用决定了其可以作为很好的药物靶标. 关于rNMBR与内源性激动剂神经介素B (neuromedin B, NMB)以及与非肽类拮抗剂pd168368作用机制的研究对于合理设计受体药物分子有重要的指导意义. 在这一研究中, 我们使用同源模建, 构建受体的三维结构, 进行分子对接和分子动力学的计算. 基于受体三维结构, 通过10 ns的空载受体、激动剂-受体、拮抗剂-受体的分子动力学模拟, 探讨受体与激动剂与拮抗剂的作用机制. 研究表明rNMB-R中跨膜(transmembrane, TM)螺旋3, 5, 6, 7参与配体的结合. NMB与受体的结合, 使受体转变为活性构象, 而受体同拮抗剂pd168368恰好相反.     

凝血因子Xa的S4口袋部分关键残基对利伐沙班结合的不同作用机制

通过生物信息学对比、 分子动力学模拟和结合自由能计算分析了利伐沙班与凝血因子Xa的S4口袋部分关键残基之间动态相互作用的细节. 结果表明, 利伐沙班与凝血因子Xa结合不稳定是由S4口袋关键残基突变对疏水盒子完整性的破坏所致. 其中Trp215侧链的疏水作用对抑制剂结合的作用较大, 但对整体结构的影响短时间内较小. Tyr99虽然在结合自由能中贡献较小, 但其突变可能导致99 loop所在结构域的整体构象变化, 从而对于抑制剂或底物的结合特异性产生影响. S4口袋关键残基的不同作用在凝血因子Xa直接抑制剂的药物设计及其拮抗剂的开发中应予以充分考虑.     

选择性M3受体拮抗剂的研究进展

M3受体是毒蕈碱型乙酰胆碱受体的亚型之一,在人体内分布广泛。选择性M3受体拮抗剂可以竞争性地与M3受体结合,主要用于膀胱过度活动症(OAB)、慢性阻塞性肺病(COPD)和肠道易激综合症(IBS)等疾病的治疗。与非选择性拮抗剂相比,选择性M3受体拮抗剂对中枢神经以及心脏的副作用大大降低。本文对已上市及处在不同研究阶段的选择性M3受体拮抗剂进行了综述。     

毒蕈碱型M1受体的同源模建和分子对接

采用同源模建方法对M1受体的三维结构进行了模拟, 将得到的模型分别与M受体完全激动剂乙酰胆碱和M1受体选择性激动剂占诺美林进行分子对接, 形成非特异性激动和特异性激动的受体-配体复合物. 用分子动力学模拟方法分别将未与小分子对接的M1受体、M1受体-乙酰胆碱复合物、M1受体-占诺美林复合物置于磷脂双膜中模拟10 ns. 将模拟后的蛋白质结构与包含活性分子的测试库对接并将结果打分, 以top5%富集因子(EF)作为评价依据, 用占诺美林优化后的M1受体模型的EF为8.0, 用乙酰胆碱优化后M1受体模型的EF为6.5, 非复合物的EF为1.5. 说明M1受体选择性激动剂复合物进行分子动力学模拟后得到的三维结构模型比较合理, 可以作为化合物虚拟筛选的模型对新化合物进行虚拟筛选, 为找到新的选择性M1受体激动剂奠定了基础.     

毒蕈碱型M1受体的同源模建和分子对接

采用同源模建方法对M1受体的三维结构进行了模拟,将得到的模型分别与M受体完全激动剂乙酰胆碱和M1受体选择性激动剂占诺美林进行分子对接,形成非特异性激动和特异性激动的受体-配体复合物.用分子动力学模拟方法分别将未与小分子对接的M1受体、M1受体-乙酰且H碱复合物、M1受体-占诺美林复合物置于磷脂双膜中模拟10 ns.将模拟后的蛋白质结构与包含活性分子的测试库对接并将结果打分,以top5%富集因子(EF)作为评价依据,用占诺美林优化后的M1受体模型的EF为8.0,用乙酰胆碱优化后M1受体模型的EF为6.5,非复合物的EF为1.5.说明M1受体选择性激动剂复合物进行分子动力学模拟后得到的三维结构模型比较合理,可以作为化合物虚拟筛选的模型对新化合物进行虚拟筛选,为找到新的选择性M1受体激动剂奠定了基础.     

中药活性成分对血栓素A2受体抑制作用的分子模拟

中药中黄酮类化合物和白藜芦醇等活性成分对血栓素A2受体具有抑制作用,但具体机理不详.本研究通过同源模建方法,以墨鱼视紫红质蛋白为模板,构建血栓素A2受体的蛋白质结构模型.并使用分子对接方法研究中药活性成分白藜芦醇和芹菜苷元与血栓素A2受体模型的作用方式,据此建立药效团模型,筛选其他潜在的血栓素A2受体抑制剂.结果表明:白藜芦醇等中药活性成分能与血栓素A2受体活性口袋中的残基发生氢键作用,结合方式与血栓素相似.血栓素与Ser201、Leu198、Arg295和Thr298发生氢键作用,白藜芦醇等活性成分与Ser201、Leu198和Arg295发生氢键作用.建立的药效团模型由7个药效元素以及排斥性空间元素组成,经测试对高活性的血栓素A2受体抑制剂有比较好的选择性.使用该药效团模型对中药天然产物数据库进行筛选,命中了一批可能具有血栓素A2受体抑制作用的活性化合物.其中一些已经报道有抑制血小板凝聚活性.本研究表明血栓素A2受体可能是活血化瘀类中药的一个潜在的靶点.     

核酸前体及其修饰结构的电子转移机理研究

应用荧光淬灭和激光光解瞬态吸收光谱技术研究了一系列核酸前体(核酸碱基、核苷及其结构修饰物)、小牛胸腺ctDNA与各种荧光探针及蛋白酶之间的瞬态、稳态电子转移作用机理。测定结果表明,它们的稳态、静态荧光淬灭作用很强,很好地符合Stern-Volmer线性方程,淬灭速率常数,k~q(s)和k~q(d),达10^10.M^-^1S^-^1,属于扩散控制,表明核酸前体的基态可作为电子受体或给体而分别与含色氨酸残基的蛋白酶、受电子型荧光探针之间发生具有电子转移性质的相互作用。对鸟嘌呤的结构修饰物进行了激光光解的瞬态吸收光谱研究,检测了几类活性中间体,论证了激发态的光致电子转移和能量转移机理。     

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.     

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%).     

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.     

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.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.