光谱法研究盐酸麻黄碱及盐酸伪麻黄碱与人血清白蛋白的键合

在模拟人体生理条件下,采用紫外光谱法、荧光光谱法和同步荧光光谱法研究盐酸麻黄碱及盐酸伪麻黄碱与人血清白蛋白(HSA)的结合作用.实验表明:盐酸麻黄碱和盐酸伪麻黄碱对HSA的荧光猝灭机制均为静态猝灭,盐酸麻黄碱和盐酸伪麻黄碱与HSA均形成1∶1复合物,结合常数K分别为2.53×104 L·mol-1和2.02×104 L...     

高圣草素-7-O-β-D-芹糖基(1→2)-β-D-葡萄糖苷与血清白蛋白相互作用研究

在模拟人体生理条件下,应用紫外吸收光谱、荧光光谱和同步荧光光谱法研究高圣草素-7-O-β-D-芹糖基(1→2)-β-D-葡萄糖苷(HAG)与牛血清白蛋白(BSA)及人血清白蛋白(HSA)的结合作用。结果表明:HAG对BSA和HSA的内源荧光均有显著的猝灭作用,且猝灭机理主要为静态猝灭。HAG与BSA和HSA的结合常数K分别为3.03×104L.mol-1和6.22×104L.mol-1,结合位点数n分别为0.858和0.911,结合距离r分别为2.88 nm和3.09 nm,其作用力以氢键和范德华力为主。利用同步荧光技术考察了HAG对BSA和HSA构象的影响。     

药物小分子白杨素与人血清白蛋白结合作用的光谱法研究

应用荧光光谱法、共振瑞利散射光谱法和同步荧光法,研究了生理条件下白杨素与人血清白蛋白(HSA)相互作用.研究表明,白杨素与HSA发生作用并形成了新的基态化合物,静态猝灭是导致HSA内源荧光猝灭的主要原因;求得不同温度 (17℃、26℃和35℃) 下白杨素与HSA作用的结合常数分别为2.373×106、1.680×106和1.346×106 L·mol-1;由求得的热力学参数,确定了白杨素与HSA间的结合反应主要由静电引力驱动.根据Frster非辐射能量转移理论,计算出白杨素在蛋白质中的结合位置与214位色氨酸残基间的距离为3.52 nm;同步荧光光谱表明,白杨素使得HSA的二级结构发生了变化.     

三种查尔酮类化合物与人血清白蛋白相互作用及其构效关系研究

在模拟人体生理条件下,采用紫外光谱法、荧光光谱法和同步荧光光谱法研究查尔酮、4′-甲氧基查尔酮和4′-氯查尔酮与人血清白蛋白(HSA)的相互作用及其构效关系。实验表明:三种查尔酮类化合物对HSA的荧光猝灭机制主要为静态猝灭,与HSA均形成1∶1复合物,结合常数K分别为2.50×104、0.697×104和0.277×104 L.moL-1,结合距离r分别为3.78、3.93和4.25nm,其作用力均以氢键和范德华力为主。查尔酮类化合物中取代基的不同对其与HSA的结合产生影响,其作用力大小依次为查尔酮>4′-甲氧基查尔酮>4′-氯查尔酮。     

还原型辅酶烟酰胺腺嘌呤二核苷酸与人血清白蛋白相互作用的研究

运用荧光光谱、紫外光谱和计算机模拟分子对接等技术,研究了在模拟生理条件下还原型辅酶烟酰胺腺嘌呤二核苷酸(NADH)与人血清白蛋白(HSA)的作用方式及热力学特征。结果表明,NADH与人血清白蛋白的荧光猝灭机理属于静态猝灭;NADH与HSA在温度283K和310K时的结合常数和结合位点数分别为1.972×104 L.mol-1、0.9657和1.468×104 L.mol-1、0.9105,通过热力学计算得到反应的热力学参数;同步荧光光谱表明NADH使色氨酸残基的微环境亲水性增强;分子模型研究表明,二者通过疏水力、静电力和氢键共同作用结合。     

烟碱与人血清蛋白相互作用的光谱研究

在0.1 mol/L的磷酸氢二钠-柠檬酸体系中,采用荧光光谱、紫外吸收光谱研究了人血清蛋白与烟碱的相互作用.荧光滴定表明这种相互作用使HSA的内源荧光猝灭.通过猝灭常数、结合常数和结合位点数的计算,证明了这种猝灭为静态猝灭机制.尼古丁和HSA形成11稳定复合物;考察不同温度和酸度下的猝灭作用,进一步证实其静态猝灭行为和疏水作用机制.紫外吸收光谱和同步荧光光谱表明,相互作用引起HSA构象变化,而同步荧光光谱提示结合位点更接近于色氨酸.     

中药成分五味子甲素及其金属离子复合物与血清白蛋白相互作用的研究

在模拟人体生理条件下,采用紫外光谱法、荧光光谱法和同步荧光光谱法研究五味子甲素及其金属离子复合物与血清白蛋白(SA)的结合作用。结果表明:五味子甲素与金属离子形成1∶1复合物;五味子甲素对SA的荧光猝灭机制为静态猝灭和非辐射能量转移;五味子甲素与牛血清白蛋白(BSA)和人血清白蛋白(HSA)的结合常数K、结合位点数n、结合距离r分别为3.58×104L·mol-1和6.42×103L·mol-1、0.944和0.993、2.18nm和1.63nm,其作用力以氢键和范德华力为主。同步荧光光谱法的结果表明:结合位点靠近色氨酸,并使色氨酸的疏水性减弱。共存金属离子对五味子甲素与SA的相互作用有一定的影响。     

甲基橙皮苷和人血清白蛋白相互作用的光谱研究

利用荧光光谱法和红外光谱法研究了甲基橙皮苷(MH)与人血清白蛋白(HSA)的相互作用.结果表明,MH对HSA的荧光有较强的猝灭作用.在296、303、310K温度下,MH与HSA相互作用的结合常数分别为1.77×104,2.65×104,3.53×104 L·mol-1.热力学分析结果表明,MH与HSA之间的结合过程是吸热的并且是自发的;作用力以疏水作用为主,并伴随氢键作用.     

杜鹃素新结构衍生物与人血清白蛋白相互作用的光谱及分子对接

采用光谱法及分子对接法考察了该化合物与人血清白蛋白(HSA)的相互作用。荧光光谱分析表明,DJS-NO_2对HSA的荧光有明显的猝灭作用,其机制属于静态荧光猝灭;温度为25℃和37℃时,猝灭常数分别为6.691×10~(13)mol/(L·s)和3.433×10~(13)mol/(L·s);结合常数分别为4.914×10~5mol/L和4.610×10~5mol/L,具有一个结合位点。热力学分析表明,该化合物与HSA之间的结合以疏水作用力为主;三维荧光光谱分析表明DJS-NO_2导致HSA氨基酸残基微环境和二级构象发生变化。圆二色谱分析显示二者的结合使得HSA的α-螺旋含量减少,提示HSA构象发生变化。分子模拟结果显示DJS-NO_2主要与HSA的位点I结合,且该化合物通过氢键与ALA118结合最紧密。     

噻螨酮与人血清白蛋白的作用机制

用分子对接方法及紫外-可见吸收光谱、同步荧光光谱、三维荧光光谱等实验手段研究了噻螨酮(HEX)与人血清白蛋白(HSA)的相互作用及对HSA构象的影响.预测结果表明,HEX能与HSA发生相互作用,且作用位点site II比site I的打分小约4.5.实验结果表明,HEX猝灭HSA的内源荧光且作用机制为静态猝灭;HEX使HSA周围的微环境发生变化,导致蛋白质的肽链结构改变;298和291 K时HEX与HSA相互作用的结合常数(KA)和结合位点数分别为7.35×103 mol/L、0.82和1.02×104 mol/L、0.86,证实HEX仅在site II存在作用位点;HEX与Trp214的结合距离为3.01 nm,作用力主要为氢键、范德华力和疏水作用力.这些研究所获得的多种信息有助于在分子水平上理解农药对人体造成的毒性及可能的生物累积性.     

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.     

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.     

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.     

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.     

Microwave-assisted copper-catalyzed stereoselective ring expansion of three-membered heterocycles with α-diazo-β-dicarbonyl compounds

Microwave-assisted copper-catalyzed ring expansions of three-membered heterocycles with α-diazo-β-dicarbonyl compounds were investigated. Thiiranes generated 3-acyl-5,6-dihydro-1,4-oxathiines in the presence of copper sulfate and trans-3-acyl-5,6-dihydro-1,4-oxathiines as stereospecific products for 1,2-disubstituted cis-thiiranes through an intramolecular S_N2 process. Oxiranes gave rise to 2-acyl-5,6-dihydro-1,4-dioxines under the catalysis of copper hexafluoroacetylacetonate and cis-3-acyl-5,6-dihydro-1,4-dioxines as stereospecific products for 1,2-disubstituted cis-oxiranes via an intimate ion-pair mechanism. The current method provides a direct and simple strategy in efficient preparation of 3-acyl-5,6-dihydro-1,4-oxathiines and 2-acyl-5,6-dihydro-1,4-dioxines, important agents in medicinal and agricultural chemistry, from readily available thiiranes and oxiranes, respectively.     

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.