光谱法研究两种抗菌类药物对牛血清白蛋白结构变化的影响

利用荧光猝灭光谱、同步荧光光谱、三维荧光光谱、紫外-可见吸收光谱及圆二色谱法研究了磺胺甲恶唑(Sulfamethoxazole,SMX)、磺胺二甲嘧啶(Sulfamethazine,SMZ)对牛血清白蛋白(Bovine serum albumin,BSA)结构的影响。荧光猝灭实验结果表明SMX和SMZ可以使BSA发生荧光猝灭;通过同步荧光光谱、三维荧光光谱和紫外-可见光谱实验数据定性的证实了SMX和SMZ的加入会使BSA的构象发生变化,并且通过紫外-可见光谱的实验结果可知SMX和SMZ与BSA之间的作用机理为静态猝灭。此外,由圆二色谱法得到的定量结果可知:当SMX或SMZ与BSA之间的摩尔浓度比为4∶1时,SMX可使BSA的α-螺旋结构含量由53.77%降低到51.82%;SMZ可使BSA的α-螺旋结构含量由53.77%降低到47.59%。     

烷基咪唑型离子液体与牛血清白蛋白的相互作用研究

应用荧光光谱、紫外吸收光谱、傅立叶变换红外光谱和核磁共振波谱研究了烷基咪唑型离子液体[bmim][PF6]及其前体物质[bmim]Cl与牛血清白蛋白(BSA)分子间的相互作用.研究表明:在生理pH值条件下,[ bmim][ PF5]和[bmim] Cl均对BSA的内源性荧光产生猝灭,其猝灭程度[bmim][ PF6]＞...     

1,4-二甲基-6,8-二甲氧基-9,10-蒽醌的合成及其与牛血清白蛋白和DNA的相互作用

合成了大黄素类蒽醌衍生物1,4-二甲基-6,8-二甲氧基-9,10-蒽醌(1)并应用紫外光谱、荧光光谱、圆二色谱等方法研究了其与牛血清白蛋白(BSA)和小牛胸腺DNA(ct-DNA)的相互作用.荧光光谱结果表明,化合物1与BSA的相互作用主要以静态猝灭方式使BSA的内源性荧光发生猝灭;圆二色谱表明,化合物1通过疏水作用及形成氢键破坏了α-螺旋结构,导致BSA分子中的α-螺旋含量下降.在pH 7.4时固定DNA的浓度,加入化合物1后,紫外光谱的最大吸收峰发生红移且吸光度加大.荧光光谱表明,化合物1与DNA-4S green NC的结合为竞争性抑制,并可使溶液体系荧光猝灭;圆二色谱表明,随着化合物1的加入,DNA碱基间作用能迅速减弱,表明化合物1与DNA之间为嵌插作用.此外,MTT方法的结果表明,化合物1对结肠癌细胞株HCT116增殖有明显的抑制作用.     

光谱法研究牛血清白蛋白与磷钼酸的相互作用

运用UV-Vis光谱、荧光光谱、同步荧光光谱、FT-IR光谱等手段,研究了在模拟人体生理条件下,牛血清白蛋白(BSA)与磷钼酸的相互作用。UV-Vis光谱显示,加入磷钼酸后,BSA的紫外吸收降低且吸收峰红移,表明磷钼酸与BSA形成了复合物;荧光猝灭光谱显示磷钼酸对BSA有荧光猝灭作用,且其荧光猝灭机理符合静态机制,磷钼酸与BSA结合的结合常数为:Ks=2.539×104L·mol-1;探针实验表明磷钼酸与BSA在结合位点I发生结合;Fster偶极-偶极非辐射能量转移机理确定了磷钼酸在BSA中与第214位色氨酸残基之间的距离r=1.93nm;FT-IR光谱显示磷钼酸诱导BSA的二级结构发生了变化,α-螺旋含量降低。     

光谱法研究萘酰亚胺类衍生物与牛血清白蛋白的相互作用

采用荧光光谱、紫外-可见吸收光谱、红外光谱和圆二色光谱研究了3-氨基-4-二甲氨基-N-丁基-1.8-萘酰亚胺(ADBN)与牛血清白蛋白(BSA)结合反应的特征。荧光光谱与紫外-可见吸收光谱表明,ADBN使BSA荧光猝灭的机理为静态猝灭。根据热力学参数判断ADBN与BSA主要是通过氢键和范德华力结合,结合距离为4.08 nm。同步荧光光谱、圆二色光谱以及红外光谱表明,结合过程中BSA的构象发生了变化。     

薰衣草花色苷与牛血清蛋白非共价相互作用研究

采用荧光光谱和紫外-可见光谱法研究了薰衣草花色苷与牛血清白蛋白(BSA)之间的相互作用。结果表明:薰衣草花色苷对BSA有较强的内源荧光猝灭作用,其猝灭机制为静态猝灭,并伴有非辐射能量转移。在298,303和310 K时,荧光猝灭速率常数分别为1.65×10~4、0.98×10~4和0.78×10~4L·mol~(-1)、结合常数(Ka)分别为40680.85、14789.38和7598.01 L·mol~(-1)及对应的结合位点数(n)分别为1.09116、1.06521和0.97505。通过计算热力学参数可推断薰衣草花色苷与BSA之间的主要作用力为氢键和范德华力。同步荧光光谱和紫外-可见光谱表明薰衣草花色苷主要影响BSA氨基酸残基所处的微环境,特别是疏水作用减弱,从而改变了BSA的分子构象。另外,通过加入外源性金属Zn~(2+)离子,进一步证明了以上研究结果。     

荧光法研究偏钒酸钠与牛血清白蛋白的相互作用

本文用荧光光谱和紫外可见吸收光谱研究了在模拟人体生理条件下，偏钒酸钠与牛血清白蛋白(BSA)结合反应的特征，研究了紫外灯(253.7 nm)照射对偏钒酸钠与BSA结合的影响。紫外吸收光谱显示，加入偏钒酸钠后，牛血清白蛋白的紫外吸收降低，表明偏钒酸钠与BSA形成了缔合物。荧光猝灭光谱显示偏钒酸钠对牛血清白蛋白有较强的荧光猝灭作用，荧光猝灭机理符合静态机制。缔合物的稳定常数分别为：K_s=0.357×10⁴(25 ℃)，K_{s相似文献}   

桂皮酸-8-羟基喹啉稀土配合物的合成、表征及与牛血清白蛋白的作用

合成了以桂皮酸、8-羟基喹啉为配体,以镱、铕为中心离子的稀土配合物,采用元素分析、摩尔电导、红外光谱、紫外光谱和荧光光谱法进行表征,并采用紫外光谱和荧光光谱研究了配合物与牛血清白蛋白(BSA)的相互作用。结果表明,随着配合物浓度的增加,BSA紫外光谱表现出明显的增色效应,配合物可有规律地猝灭BSA的荧光。     

间苯二酚与牛血清白蛋白的作用机理

采用荧光和紫外光谱法研究了间苯二酚与牛血清白蛋白(BSA)的相互作用。间苯二酚使BSA的构象发生改变,α-螺旋含量减小。同步荧光光谱发现间苯二酚使BSA色氨酸残基的疏水性降低,酪氨酸残基的疏水性增强。荧光光谱表明猝灭机理为静态猝灭,计算了复合物的结合常数,通过热力学参数得出间苯二酚与BSA之间的作用力主要是静电作用力。     

槲皮素-铝配合物的制备及其与BSA的结合作用

在甲醇溶液中合成了槲皮素-铝配合物(Que-Al),并用紫外-可见吸收光谱和红外光谱进行了表征;运用荧光光谱探讨了Que-Al与牛血清白蛋白(BSA)的相互作用;求得了结合常数KA和热力学参数△H、△G、和△S.结果表明,Que-Al对BSA具有荧光猝灭作用,其猝灭方式为动态猝灭;Que-Al与BSA之间的作用力主要为疏水作用力.     

A carbanion induced synthesis of highly congested pyrazole and imidazole containing heterocycles

An efficient approach to the synthesis of highly congested di, penta and hexacyclic pyrazoles as well as imidazole fragment containing novel heterocyclic molecule has been developed through a carbanion induced transformation of suitably functionalized 2H-pyran-2-ones, benzo[h]chromene and thiochromeno[4,3-b]pyrans. Due to the presence of fluorescence, we report their prime application metal sensor as off/on switching in ferric ions.     

Selective synthesis of 4,5-dihydroimidazo- and imidazo[1,5-a]quinoxalines via modified Pictet–Spengler reaction

An efficient tandem approach for the selective synthesis of 4,5-dihydroimidazo[1,5-a]quinoxalines 6a–g and imidazo[1,5-a]quinoxalines 7a–h by the reaction of 2-imidazolyl anilines 4a–c with aryl aldehydes 5a–k under mild reaction conditions is described. Introduction of electron releasing alkyl groups in substrates 4a–b was found to be instrumental for the success of the reaction.     

Understanding the Diels-Alder reactivity of 1,2-azaborine analogues

The Diels-Alder reactivity of 1,2-heteroborines (H₄C₄B(H)X, X?=?NH, PH, AsH; O, S, Se) has been computationally explored by means of Density Functional Theory (DFT) calculations. The influence of the HB?=?X fragment on the reactivity of the system has been quantitatively analyzed in detail by means of the so-called Activation Strain Model (ASM) of reactivity. It is found that the interaction between these species and the dienophile is significantly stronger than that computed for their all-carbon isoelectronic counterpart, benzene. In addition, the strain energy plays a key role in the observed reactivity trends. The role of the aromaticity strength of these heteroarenes on the reactivity is also assessed.     

Synthesis of N-substituted carbazolones from α-iodo enaminones via Pd(0)-catalyzed intramolecular coupling under microwave irradiation

A variety of N-aryl and N-alkyl carbazolones were conveniently achieved in good to high yields via Pd₂(dba)₃-mediated intramolecular coupling of N-substituted α-iodo enaminones under microwave irradiation. The Pd(0)-catalyzed cyclization was found to proceed favorably with the more electron-deficient phenyl ring during the reactions involving unsymmetrical N,N-diaryl α-iodo enaminones. This unique property enables the construction of carbazolone skeleton containing nitro substituted benzenoid ring.     

Synthesis of substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles by intramolecular nitrilimine cycloaddition

Both substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles have been synthesized by the 3+2 intramolecular dipolar cycloaddition of nitrilimines to alkynes. This cyclization has been extended to more versatile 3-bromo derivatives by the use of alkynylbromides as dipolarophiles.     

Catalyst free,visible-light promoted photoaddition reactions between C60 and N-trimethylsilylmethyl-substituted tertiary amines for synthesis of aminomethyl-1,2-dihydrofullerenes

An efficient and benign method for the preparation of aminomethyl-substituted fullerenes has been developed. The process, involving catalyst free, visible-light irradiation of 10% EtOH-toluene solutions containing fullerene C₆₀ and N-trimethylsilylmethyl-substituted amines by using a 20 W compact fluorescent lamp, leads to formation of aminomethyl-substituted fullerene adducts in a highly efficient manner. The photoaddition reaction takes place via a pathway initiated by visible light absorption by C₆₀, followed by SET from the amine to the triplet excited state of C₆₀. Ethanol-promoted desilylation of the resulting a minimum radical then generates the corresponding α-amino radical which couples with the C₆₀ radical anion to form the anion precursor of the fullerene adducts. The new approach using visible-light takes place under mild conditions and it does not require the use of photocatalysts. Thus, the method developed in this effort could broadens the range of functionalized fullerene derivatives that can be readily prepared.     

Highly efficient and stereoselective cycloaddition of nitrones to indolyl- and pyrrolylacrylates

The reactions of various nitrones with indolyl- and pyrrolylacrylates proceeds regioselectively with high diastereoselectivity in the case of aldonitrones, and represents an effective method for obtaining new indolyl- and pyrrolyl-substituted isoxazolidine carboxylates stabilized by weak (CH?O) and moderate (NH?N) strength intramolecular hydrogen bonding. The resulting cycloadducts exhibit promising in vitro anti-influenza activities.     

Transition metal-free direct amination of benzoxazoles using formamides as nitrogen sources

A transition metal-free method for the direct amination of benzoxazoles using formamides as nitrogen sources is reported, which was mediated by an inexpensive and environmentally friendly tetrabutylammonium iodide/tert-butyl hydroperoxide system and gave the 2-aminobenzoxazole derivatives with moderate to good yields.     

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.     

l-Proline-catalyzed five-component domino reaction leading to multifunctionalized 1,2,3,4-tetrahydropyridines

Multifunctionalized 1,2,3,4-tetrahydropyridines are concisely synthesized in good yields via l-proline-catalyzed or l-proline/FeCl₃-cocatalyzed one-pot multicomponent reactions (MCRs). The MCRs involve a domino hydroamination/prins reaction/Mannich-type reaction/intramolecular dehydration-cyclization process. The molecular structure of 5baa, one of multifunctionalized 1,2,3,4-tetrahydropyridines, was confirmed by single-crystal X-ray diffraction.