电化学方法研究多粘菌素B与磷脂酰胆碱的相互作用

采用电化学方法研究了一种多肽类抗生素多粘菌素B(PMB)与模拟生物膜硫醇-磷脂酰胆碱杂化双层膜之间的相互作用。PMB可与磷脂酰胆碱发生强相互作用,破坏双层膜结构,从而使膜的通透性升高。PMB的浓度、酸度、与膜的作用时间及膜中胆固醇的存在均影响二者的作用程度。另外,膜的自修复实验表明,被PMB破坏的双层膜电极在一定程度上可以在KCl溶液中重新自组装,且自修复的程度和修复时间及与之相互作用的PMB的浓度有关。     

硫醇－磷脂混合双层膜的电化学性质及其与蜂毒素的相互 作用研究

报道了硫醇－磷脂混合双层膜的循环伏安和电化学交流阻抗行为研究,并用电化学方法考察了蜂毒素与其相互作用,实验中通过冷冻表面沾有磷脂溶液的硫醇单层膜制备混合双层膜,研究表明双层膜在电极表面形成致密的绝缘层,阻碍了电极表面的电子传递,在双层膜体系上引入的蜂毒素可在膜表面上形成孔洞,破坏膜的绝缘性,降低膜电阻,增加膜电容,使带负电的探针Fe(CN)6^3-的氧化还原反应速度加快。     

脱氧胆酸钠与支撑磷脂双层膜作用的电化学研究

以支撑磷脂双层膜(supported bilayer lipid membrane, s-BLM)作为生物膜模型, 采用循环伏安法和交流阻抗技术研究了脱氧胆酸钠(sodium deoxycholate, NaDC)与s-BLM的相互作用. 结果表明, NaDC能降低磷脂分子的有序性, 诱发s-BLM上形成孔洞或缺陷, 并且它们之间的这种相互作用对作用时间、NaDC溶液的浓度和pH值以及胆固醇的存在与否具有依赖性, 并且作用后的s-BLM在0.1 mol/L的KCl溶液中能够自我修复, 这表明NaDC与s-BLM的相互作用是可逆的.     

十二烷基磺基甜菜碱与铂电极支撑的磷脂双层膜作用的电化学研究

以铂电极支撑的磷脂双层膜(Supported Bilayer Lipid Membrane,s-BLM)作为生物膜的模型,以Fe(CN)36-和Fe(CN)64-为探针分子,利用循环伏安法(CV)和交流阻抗谱(EIS)研究两性表面活性剂十二烷基磺基甜菜碱(Dodecyl Sulfobetaine,DSB)对s-BLM相互作用。结果显示,DSB可以嵌入到s-BLM的疏水区,容易使其表面分子的排列发生变化,产生缺陷或孔洞,探针分子Fe(CN)63-和Fe(CN)64-可以通过这些微孔接近电极,产生氧化还原响应。并且作用时间、DSB的浓度以及胆固醇的存在与否对二者的相互作用有直接影响。此外作用后的双层膜在0.1mol/LKCl溶液中能够自我修复,这表明DSB与s-BLM的相互作用是可逆的。     

非支撑磷脂双层膜制备及温度对其力学性质的影响

结合聚苯乙烯球刻蚀和微机电系统技术加工氮化硅纳米多孔膜, 并在其上用囊泡法制备非支撑磷脂双层膜, 通过温控原子力显微术(AFM)的成像模式和力曲线模式对非支撑磷脂双层膜的形貌和力学性质进行研究. 实验结果表明, 该方法制备的非支撑磷脂双层膜具有流动性, 能进行自我修复, 该特点有利于提供足够的非支撑磷脂双层膜区域用于其性质研究; 非支撑磷脂双层膜的膜破力和粘滞力均随着温度的升高而减小, 即膜的机械稳定性随着温度的升高而降低. 非支撑磷脂双层膜膜破力小于支撑磷脂双层膜的膜破力, 并且非支撑磷脂双层膜粘滞力随温度的变化趋势与支撑磷脂双层膜的变化趋势相反.     

金(111)电极表面浮动磷脂双层膜的原位偏振红外反射光谱研究(英文)

应用电化学原位偏振红外反射光谱法研究了构建于金(111)电极表面的浮动磷脂双层膜.金电极表面先自组装一层巯基葡萄糖单层来增加表面的亲水性,浮动磷脂双层膜通过LB-LS技术构建在巯基葡萄糖单层上.双层膜由双肉豆蔻磷脂酰胆碱(DMPC)、胆固醇和神经节苷脂GM1构成.GM1分子中的糖链可以物理吸附在巯基葡萄糖表面,在双层膜和基底间形成一个富含水的隔层.红外光谱表明浮动双层膜中的DMPC分子比传统的支撑双层膜中的DMPC分子有更强的水合作用,证实了双层膜和基底间水层的存在.该浮动双层膜更接近于实际的生物膜体系,并且在金电极表面有宽的电位区间,非常适于进一步的离子通道蛋白质研究.     

高效液相色谱测定大鼠肺细胞膜磷脂

磷脂酰胆碱(phosphatidylcholine,PC)和磷脂酰丝氨酸(phosphatidylserine,PS)是膜磷脂家族中的重要成分。它们对细胞膜中蛋白激酶C(proteinkinase C,PKC)的激活有着重要的调节作用,其浓度上的变化对PKC系统产生激活或抑制作用。本工作用高效液相色谱测定了大鼠肺细胞膜中的磷脂含量。     

稀土离子及其配合物与磷脂脂质体的相互作用

用核磁共振(NMR)方法研究了稀土离子及其配合物与二棕榈酰磷脂酰胆碱(DPPC)和鞘磷脂(SPM)脂质体的相互作用.磷脂极性头平行于膜平面.稀土离子与磷脂极性头P—O键键合,与经典模型不同,键合后极性基团仍平行于膜平面,而不是垂直于膜平面.稳定的稀土配合物对磷脂脂双层结构影响很小.将稀土离子引入磷脂脂质体和小分子配体的混合物中,稀土首先与小分子配体配位.     

微生物脂肽与磷脂的混合单分子膜性质

研究了一种微生物脂肽--表面活性素与二肉豆蔻酰磷脂酰胆碱(DMPC)在气,液界面形成的混合单分子膜性质.测定了混合单分子膜的表面压.分子面积(л-A)曲线,根据л-A曲线获得了不同表面压下混合单分子膜的过剩面积(Aex)和混合过剩自由能(△Gmex)与混合单分子膜中表面活性素摩尔分数的关系.Aex和△Gmex的计算结果均表明,表面活性素与DMPC在纯水亚相上形成的混合单分子膜中不相容,二者之间 的相互作用主要是排斥力.通过原子力显微镜观察了在表面压15mN/m下的混合单分子膜的LB膜,发现表面活性素与DMPC发生了微相分离,说明二者在混合膜中的烷基链取向不同,这可能是二者发生排斥作用的主要原因之一.此外,还研究了亚相pH对混合单分子膜相容性的影响,发现表面活性素与DMPC在混合单分子膜中的相容性在碱性环境下增强,这可能与二者极性头基之间的相互作用有关.     

磷脂酰胆碱与牛血清白蛋白相互作用的FT-IR研究

利用傅立叶变换红外(FT-IR)和拉曼(FT-Raman)光谱研究了高浓度磷脂酰胆碱(PC)与牛血清白蛋白(BSA)的相互作用,及Eu3＋对该作用的影响.FT-IR结果显示,PC/BSA混合体系中二者的相互作用主要发生在PC头部极性基团,且这一作用随BSA含量的增加而增强,作用后蛋白质二级结构中α螺旋的比例有所增加. FT-Raman光谱说明PC与BSA的相互作用影响磷脂CH链的排列有序程度. PC/BSA/Eu3＋体系的红外光谱显示, Eu3＋与PC的磷氧键发生了强相互作用,并使蛋白α螺旋的比例进一步增加.     

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.     

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.     

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.     

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.     

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.