碳氢与碳氟表面活性剂混合水溶液的胶团与囊泡形成

碳氢与碳氟表面活性剂混合水溶液的胶团与囊泡形成丁慧君，戴群英，张兰辉，赵国玺（北京大学物理化学研究所，北京，１００８７１）关键词囊泡，表面活性剂，胶团形成，负离子结合度，表面活性利用结构简单的表面活性剂代替生物膦脂形成人工囊泡的研究正受到普遍关注［１...     

脂肪酸盐-烷基吡啶盐混合体系的双水相

研究了脂肪酸盐和烷基吡啶盐混合水溶液中双水相的形成规律和性质．考察了形成双水相的组成范围和烷基碳链长的影响。测定了两相的密度及化学组成．应用电子显微镜观察了两相的微观结构．结果表明,两相均存在囊泡结构．两相含水均在95％以上．上相为表面活性剂富集的囊泡絮凝相,浓度远远大干下相,相差均在二十倍以上．下相为含有分散的囊泡的表面活性剂稀溶液．     

类水滑石诱导囊泡的自发形成

报道了一种新的囊泡合成方法——荷电固体纳米颗粒诱导囊泡的自发形成. 研究发现, 将5.0 g/L带结构正电荷的Mg₃Al类水滑石(HTlc)溶胶和0.02 mol/L由两性表面活性剂十二烷基甜菜碱(C₁₂BE)和阴离子表面活性剂双(2-乙基己基)琥珀酸磺酸钠(AOT)组成的溶液(C₁₂BE与AOT物质的量比为3∶2)混合, 当HTlc溶胶与表面活性剂溶液的体积比在1∶9～4∶6范围内, 在HTlc纳米颗粒的诱导下可自发形成囊泡, 并获得稳定的HTlc-囊泡复合分散体系.     

正负离子表面活性剂混合体系中高稳定性囊泡的形成

对总浓度为0.01 mol/L，摩尔比为2：1的十二烷基硫酸钠/溴化十二烷基三乙 铵的正负离子表面活性剂混合体系形成的囊泡的稳定性进行了研究。发现这一体系 形成的囊泡在长放置（5个月）后依然存在。在加入较大量的无机盐（0.15 mol/L NaBr）、较大幅度pH变化（pH = 2～12）、温度变化（从80 ℃到-22 ℃）情况下 体系中的囊泡依然呈现出优异的稳定性。在非水溶剂乙醇（100%）中这类正负离子 表面活性剂仍然可以形成囊泡。     

环境因素对正负表面活性剂体系相行为的影响

在1:1正负离子表面活性剂混合体系(十二烷基硫酸钠/辛基三甲基溴化铵 SDS-C8NM3Br; 十二烷基硫酸钠/十二烷基三甲基溴化铵,SDS-C12NM3Br)中加入短链脂肪醇 (乙醇,正丙醇,正丁醇),正负离子表面活性剂沉淀溶解,出现表面活性剂双水相.上相有液晶存在,下相有囊泡自发形成.折光率数据和电镜结果表明:上相为表面活性剂富集相,下相表面活性剂浓度较低.混合体系中,出现表面活性剂双水相所需短链脂肪醇的体积百分数,随短链脂肪醇的链长增加而降低.温度升高,出现表面活性剂双水相所需短链脂肪醇的体积百分数降低.对SDS/C8NM3Br/H2O体系的研究结果表明:超声处理,可使混合体系中沉淀向囊泡转化,与短链脂肪醇的加入后的作用类似.     

胆固醇对卵磷脂囊泡稳定性的影响

采用透射电子显微镜研究了Gemini表面活性剂诱导卵磷脂囊泡结构改变的机理, 用Langmuir膜天平研究卵磷脂和胆固醇的不溶单分子混合膜在气-液界面的行为和混合膜分子间的相互作用, 并结合动态光散射技术和停留法探讨胆固醇对Gemini表面活性剂诱导卵磷脂囊泡结构改变的影响. 从电镜结果可以推测带正电荷的Gemini表面活性剂分子会嵌入到带负电荷的卵磷脂囊泡双分子层的外层, 囊泡的双分子层之间的相互吸引力使双分子层的厚度减少, 由于嵌入的表面活性剂分子在囊泡的双分子层中分布是不均匀的, 这种分布的不均匀性必然会导致双分子层厚度的不均匀, 从而使囊泡破裂. 混合膜的过剩面积和动力学结果表明, 胆固醇和卵磷脂是相互吸引的, 即胆固醇的加入使卵磷脂囊泡更不容易被表面活性剂破坏.     

非水溶剂中囊泡等分子有序组合体的形成

总结了各类表面活性剂在乙醇等非水及混合溶剂中的囊泡、胶束等聚集体的形成规律,着重讨论了非水体系中介电常数改变对正负离子表面活性剂混合体系中聚集体形成的影响.对反胶束等不同分子有序组合体在非水体系中的形成情况也进行了概述.     

盐引发阴离子/非离子表面活性剂复配体系中囊泡自发形成

在无盐时, 阴离子表面活性剂十二烷基苯磺酸钠(SDBS)与非离子表面活性剂壬基酚聚氧乙烯(10)醚(TX-100)的复配体系中只有混合胶束存在, 而盐的加入即可以引发体系中囊泡的自发形成, 这使得囊泡的形成变得更加简单. 引发机理可以归因于盐对离子表面活性剂的极性头双电层的压缩作用, 减少了极性头的面积, 加上非离子表面活性剂的参与使得堆积参数P增加, 导致了半径更大的聚集体的形成. 制作了SDBS/TX-100/盐水拟三元相图, 通过目测和表面张力的变化确定了囊泡形成的带状区域, 并用负染色电镜(TEM)对囊泡进行了表征, 同时测定了盐度以及相同盐度下表面活性剂浓度对囊泡粒径的影响, 发现囊泡的粒径随着盐度的增加而增加, 而在同一盐度下, 囊泡的粒径基本不受表面活性剂浓度的影响.     

仿生信号转导体系的构建:囊泡表面磷脂信号分子诱发的乳酸脱氢酶的激活

以细胞肌醇磷脂信号转导途径为原型,在合成肽脂囊泡(人工细胞膜模型)上,利用天然磷脂为信号分子,成功地激活了处于囊泡表面的乳酸脱氢酶．为此,将1,2-二-十四烷基磷脂酰乙醇胺等天然磷脂嵌入合成肽脂N,N-二-十六烷基-N^a-6-三甲胺基己酰基-L-甘氨酰胺囊泡中,制备了稳定的混合双层膜囊泡,用透射电子显微照相、动态光散射及差示扫描量热等手段确认了混合囊泡的形态及粒径分布．以磷酸吡哆醛等维生素B6类化合物为信号分子激活剂,利用它们与天然磷脂形成复合体,进而与Cu^2 形成强的金属配合物的性质,实现了对处于囊泡表面、被Cu^2 抑制的乳酸脱氢酶的激活,构建了一个新的仿生信号转导体系．紫外一可见光谱实验证实了以上结果．此外,结果还表明囊泡表面的疏水作用和静电引力是促进天然磷脂一磷酸吡哆醛复合体形成的主要因素．囊泡表面的疏水微环境作为反应场是构建此仿生信号转导体系不可缺少的要素．     

辛基三甲基溴化铵与辛基硫酸钠混合水溶液的相行为

对辛基三甲基溴化铵(OTAB)与辛基硫酸钠(SOS)正、负离子混合表面活性剂水溶液的相行为进行了研究.在高浓度的溶液中,混合表面活性剂形成液晶相,随着混合摩尔比OTAB/SOS接近于1,液晶结构由六角相转层状相,同时夹杂少量沉淀物;在中等浓度时,任意混合摩尔比例下皆为均相透明溶液;在低浓度下,在很宽的OTAB/SOS混合摩尔比的范围,出现双水相,其中的表面活性剂稀薄相,为不同大小的胶团与囊泡组成的稀溶液,另一表面活性剂富集相中则为数密度很大的囊泡聚集体,富集相对油溶性染料的增溶作用比非富集相高得多.     

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.     

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.     

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.