Gemini表面活性剂(12-6-12)和DNA的相互作用

应用紫外光谱、荧光探针、zeta 电位、动态光散射和凝胶电泳等方法探讨了阳离子gemini 表面活性剂C₁₂H₂₅N⁺(CH₃)₂―(CH₂)₆―(CH₃)₂N⁺C₁₂H₂₅·2Br^-(12-6-12)与DNA之间的相互作用. 研究结果表明, 与传统表面活性剂相比, 偶联表面活性剂特殊的分子结构使其与DNA的作用更强烈. DNA引导表面活性剂在其链周围形成类胶束结构, 开始形成类胶束时对应的表面活性剂临界聚集浓度(CAC)比纯表面活性剂临界胶束浓度(CMC)低两个数量级. CAC与DNA的浓度无关, 而与表面活性剂之间的疏水作用以及表面活性剂与DNA之间的静电吸引作用密切相关. Zeta 电位和凝胶电泳结果显示了DNA链所带负电荷逐渐被阳离子表面活性剂中和的过程. 借助原子力显微镜(AFM)成功观察到了松散的线团状DNA, 球状体随机地分散在DNA链上形成类似于串珠的结构、尺寸较大的球形复合物以及其由于吸附多余的表面活性剂重新带正电而被溶解得到的较小DNA/12-6-12聚集体. 圆二色(CD)光谱结果显示, 12-6-12可以诱导DNA的构象发生改变.     

萘基桥联有机-无机杂化介孔材料的合成及其光学性质

以短链阳离子三聚表面活性剂C₁₀H₂₁N⁺(CH₃)₂(CH₂)₂N⁺(CH₃)(C₁₀H₂₁)(CH₂)₂N⁺(CH₃)₂C₁₀H₂₁]·3Br^?为结构导向剂, 通过2,7-二(3-三乙氧硅基氨丙酯基)萘(NIS)和四乙氧基硅烷(TEOS)共缩聚, 制备了有序的萘基桥联的杂化周期性介孔有机硅(PMOs). 样品通过X射线衍射(XRD)、高分辨透射电镜(HRTEM)、氮气吸附-脱附、差示扫描量热/热重分析(DSC/TGA)表征. 结果表明, 当NIS占NIS和TEOS总量40% (摩尔分数)时, 可以形成具有结晶态孔壁的有序介孔杂化材料. 当NIS含量低于或高于40%时, 分别形成无定形孔壁的有序介孔杂化材料和无孔杂化材料. 随着孔壁中萘基基团的增加, 由于有机基团之间π-π堆积作用增强, 杂化介孔材料显示良好的热稳定性. 由于在二氧化硅骨架中嵌入荧光萘基基团, 杂化有机-无机有序介孔材料显示了激基缔合物的光学行为. 随萘基基团含量的增加, 杂化材料的紫外吸收峰发生蓝移, 形成H聚集体; 由于聚集引起的荧光淬灭, 杂化材料的荧光量子产率明显降低.     

C2(X1Σg+)自由基与不饱和碳氢化合物反应的温度效应

运用脉冲激光光解-激光诱导荧光(PLP-LIF)的方法在293-573 K的温度范围内测量了C₂(X¹Σ_g⁺)自由基与不饱和碳氢化合物(C₂H₄和C₂H₂)气相反应的双分子反应速率常数. 获得的速率常数可以用Arrhenius 公式表达如下(单位: cm³·molecule^-1·s^-1): k(C₂H₄)=(1.16±0.10)×10^-10exp[(290.68±9.72)/T], k(C₂H₂)=(1.36±0.02)×10^-10exp[(263.85±7.60)/T], 误差为2σ. 由获得的双分子反应速率常数及其所呈现的负温度效应, 我们认为在293-573 K温度范围内C₂(X¹Σ_g⁺)自由基和不饱和碳氢化合物的反应遵循加成机理.     

含氟表面活性剂溶液的动态表面张力研究

本文研究了阳离子氟表面活性剂CF₃CF₂CF₂O(CF(CF₃)CF₂O)₂CF(CF₃)CONH(CH₂)₃N⁺(C₂H₅)₂CH₃I^-(简写FC-4 )的动态表面性质，利用Krüss K12和MBP动态表面张力仪分别测定了该体系的平衡表面张力和动态表面张力。由平衡表面张力测定结果得到了临界胶束浓度和表面吸附量。利用渐进的Ward and Tordai方程对动态数据进行了分析。结果表明：在吸附的最初阶段符合扩散控制模型，而在吸附的后期，证明了吸附势垒的存在，表明在吸附后期属于混合动力学模型。计算得出25 ℃时，该体系势垒约在25到35 kJ/mol. 由于氟表面活性剂分子间作用力小，表面压是导致吸附势垒的主要原因。     

烃基取代茚基钌羰基化合物的合成及晶体结构

配体C₉H₇R(R=CH₂CH₂CH₃ (1),CH₂(CH₃)₂ (2),C₅H₉ (3),CH₂C₆H₅ (4),CH₂CH=CH₂ (5))分别与Ru₃(CO)12在二甲苯或庚烷中加热回流,得到了6个双核配合物[(η⁵-C₉H₆R)Ru(CO)(μ-CO)]₂(R=CH₂CH₂CH₃ (6),CH₂(CH₃)₂ (7),C₅H₈ (8),CH₂C₆H₅ (9),CH₂CH=CH₂ (10))和[(η⁵-C₉H₆)(H₃CH₂C)CHCH(CH₂CH₃)(η⁵-C₉H₆)] [Ru(CO)(μ-CO)]₂ (11).通过元素分析、红外光谱、核磁共振氢谱对配合物的结构进行了表征,并用X-射线单晶衍射法测定了配合物6,9,10和11的结构.     

界面扩张流变法研究C12mimBr对Gemini12-2-12在空气/水界面聚集行为的影响

采用界面扩张流变技术研究了季铵盐偶联表面活性剂C₁₂-(CH₂)₂-C₁₂·2Br (Gemini12-2-12)及其与离子液体表面活性剂溴化1-十二烷基-3-甲基咪唑(C₁₂mimBr)复配体系的动态界面张力、扩张流变性质和界面弛豫过程等, 探讨了C₁₂mimBr 对C₁₂mimBr/Gemini12-2-12 混合体系界面性质的影响及C₁₂mimBr 对Gemini12-2-12界面聚集行为影响的机制. 结果表明, 随着离子液体表面活性剂的不断引入, 体系界面吸附达到平衡所需的时间逐渐缩短, 扩张模量和相角明显降低, 界面吸附膜由粘弹性膜转变为近似纯弹性膜; 同时, 界面及其附近的弛豫过程也发生显著变化, 慢弛豫过程消失, 快弛豫过程占主导地位, 且离子液体浓度越高, 快弛豫的贡献越大. 这些界面性质的变化主要归因于离子液体表面活性剂C₁₂mimBr参与界面形成及两表面活性剂在界面竞争吸附的结果. 少量离子液体表面活性剂C₁₂mimBr 的加入可以填补疏松的Gemini12-2-12 界面上的空位, 形成混合界面吸附膜. 随着C₁₂mimBr 含量的增加, 嵌入界面的C₁₂mimBr 分子数不断增多, 导致界面上相互缠绕的Gemini12-2-12烷基链“解缠”, 在体相和界面分子扩散交换的过程中“解缠”的Gemini12-2-12分子从界面上解吸回到体相, 与此同时, C₁₂mimBr 分子相对较小的空间位阻及较强的疏水作用促使其优先扩散至界面进而取代Gemini12-2-12分子, 最终界面几乎完全被C₁₂mimBr分子所占据.     

C78(CH2)2结构和光谱的半经验和密度泛函研究

用INDO系列方法研究C₇₈(CH₂)₂的18种可能异构体，表明最稳定异构体是42,43,62,63-C₇₈(CH₂)₂,其中CH₂加在C₇₈（C_2V）椭球长轴所穿过的同一六员环的两个6/6键上，形成类环丙烷结构。并对最稳定的四种异构体用B3LYP/3-21G方法进行了结构优化,在此基础上, 用INDO/CIS方法计算的C₇₈(CH₂)₂稳定异构体的电子光谱的第一吸收峰和用AM1方法计算的碳笼上的C-C键的主要红外振动频率与C₇₈（C_2V）相比发生兰移，原因是C₇₈(CH₂)₂具有较大的LUMO-HOMO能隙和由于加成带来的共轭体系变小。在B3LYP/3-21G水平上计算的¹³C NMR谱表明,被加成的C-C键上的C原子化学位移向高场移动, 这是因为sp²杂化的C 原子被转化为 sp³杂化的C 原子.     

阿拉伯树胶对Gemini表面活性剂界面扩张流变性质的影响

利用悬挂滴方法研究了Gemini季铵盐表面活性剂(C₁₂-Ph-C₁₂和C₁₂-8-C₁₂)和阿拉伯树胶的界面张力和界面扩张流变性质, 考察了阿拉伯树胶对C₁₂-Ph-C₁₂和C₁₂-8-C₁₂溶液界面张力和界面扩张流变性质的影响. 研究结果表明, 1%(w)阿拉伯树胶的加入显著降低了C₁₂-Ph-C₁₂和C₁₂-8-C₁₂的界面张力, 但是界面扩张模量增加,这一变化主要是由于阿拉伯树胶分子与Gemini季铵盐表面活性剂分子通过静电相互作用形成复合物. 文中提出了不同结构Gemini季铵盐表面活性剂与阿拉伯树胶分子在界面排布的示意图.     

四氯合锌酸正九烷铵的晶体结构及热化学性质

合成了四氯合锌酸正九烷铵复合物(C₉H₁₉NH₃)₂ZnCl₄(s) (C₉Zn(s)), 并使用X射线单晶衍射、化学分析以及元素分析确定了其晶体结构和化学组成. 利用其晶体学数据推导了C₉Zn(s)的晶格能U_POT=952.94 kJ·mol^-1. 在298.15 K下, 利用恒温环境溶解-反应热量计测定了C₉Zn(s)在不同质量摩尔浓度下的摩尔溶解焓. 在Pitzer电解质溶液理论基础上确定了C₉Zn(s)的无限稀释摩尔溶解焓Δ_sΗ_m^∞=20.09 kJ·mol^-1, 以及Pitzer焓参数组合(4β_C9H19NH3,Cl^(0)L+2β_Zn,Cl^(0)L+θ_C9H19NH3,Zn^L)和(2β_C9H19NH3,Cl^(1)L+β_Zn,Cl^(1)L)的值.     

两个丁二肟有机锡配合物的合成、结构及抗癌活性

合成了 2 个丁二酮肟有机锡化合物:双(三(2-甲基-2-苯基丙基)锡)丁二酮肟配合物(C₆H₅C(CH₃)₂CH₂)₃Sn(ON=C(CH₃)C(CH₃)=NO)Sn(CH₂C(CH₃)₂C₆H₅)3 (1)和二苄基锡氧氯丁二酮肟多核配合物[μ₃-O-((C₆H₅CH₂)₂Sn)₂(ON=C(CH₃)C(CH₃)=NOH)(O)Cl]₂(2)。通过元素分析、红外光谱、核磁共振(¹H、¹³C、¹¹⁹Sn)、差热分析和单晶 X射线衍射对配合物进行了结构表征, 对其结构进行量子化学从头计算, 并进行了体外抗癌活性研究。结果显示:配合物 1为通过配体丁二酮肟桥联的双锡核中心对称分子, 锡原子均为四配位的畸变四面体构型; 配合物 2 为通过氧原子和丁二酮肟配体桥联的四锡核中心对称多环聚合结构, 锡原子分别为五配位的畸变三角双锥构型和六配位的畸变八面体构型。配合物对人肝癌细胞(HUH7)、人肺癌细胞(A549)、人表皮癌细胞(A431)、人结肠癌细胞(HCT-116)和人乳腺癌细胞(MDA-MB-231)均有较强的抑制活性。     

Mixed monolayers of Gemini surfactants and stearic acid at the air/water interface

The properties of mixed monolayers composed of the cationic Gemini surfactant ([C(18)H(37)(CH(3))(2)N(+)(CH(2))(3)N(+)(CH(3))(2)C(18)H(37)],2Br(+), abbreviated as 18-3-18,2Br(-1)) and stearic acid (SA) at the air/water interface were investigated by using a Langmuir film balance. The excess areas at the different mixed monolayer compositions were obtained and used to evaluate the miscibility and nonideality of mixing. Due to the electrostatic attractive interactions between 18-3-18,2Br(-1) and SA, the excess areas indicated negative deviations from ideal mixing. Moreover, 18-3-18,2Br(-1) and SA were miscible at the air/water interface, as was confirmed by atomic force microscopy (AFM) images of the LB films transferred onto mica substrates. The attenuated total reflectance (ATR) infrared spectra showed that SA in the mixed monolayers was ionized completely at a composition X(SA)=0.67 and formed a "cationic-anionic surfactant," i.e., the carboxylate, with 18-3-18,2Br(-1) owing to the electrostatic interaction between the head groups.     

Cationic Gemini surfactant at the air/water interface

The surface properties and structures of a cationic Gemini surfactant with a rigid spacer, p-xylyl-bis(dimethyloctadecylammonium bromide) ([C(18)H(37)(CH(3))(2)N(+)CH(2)C(6)H(4)CH(2)N(+)(CH(3))(2)C(18)H(37)],2Br(-), abbreviated as 18-Ar-18,2Br(-1)), at the air/water interface were investigated. It is found that the surface pressure-molecular area isotherms observed at different temperatures do not exhibit a plateau region but display an unusual "kink" before collapse. The range of the corresponding minimum compressibility and maximum compressibility modulus indicates that the monolayer is in the liquid-expanded state. The monolayers were transferred onto mica and quartz plates by the Langmuir-Blodgett (LB) technique. The structures of monolayers at various surface pressures were studied by atomic force microscopy (AFM) and UV-vis spectroscopy, respectively. AFM measurements show that at lower surface pressures, unlike the structures of complex or hybrid films formed by Gemini amphiphiles with DNA, dye, or inorganic materials or the Langmuir film formed by the nonionic Gemini surfactant, in this case network-like labyrinthine interconnected ridges are formed. The formation of the structures can be interpreted in terms of the spinodal decomposition mechanism. With the increase of the surface pressure up to 35 mN/m, surface micelles dispersed in the network-like ridges gradually appear which might be caused by both the spinodal decomposition and dewetting. The UV-vis adsorption shows that over the whole range of surface pressures, the molecules form a J-aggregate in LB films, which implies that the spacers construct a pi-pi aromatic stacking. This pi-pi interaction between spacers and the van der Waals interaction between hydrophobic chains lead to the formation of both networks and micelles. The labyrinthine interconnected ridges are formed first because of the rapid evaporation of solvent during the spreading processes; with increasing surface pressure, some of the alkyl chains reorient from tilting to vertical, forming surface micelles dispersed in the network-like ridges due to the strong interaction among film molecules.     

Structure of the complex monolayer of gemini surfactant and DNA at the air/water interface

The properties of the complex monolayers composed of cationic gemini surfactants, [C(18)H(37)(CH(3))(2)N(+)-(CH(2))(s)-N(+)(CH(3))(2)C(18)H(37)],2Br(-) (18-s-18 with s = 3, 4, 6, 8, 10 and 12), and ds-DNA or ss-DNA at the air/water interface were in situ studied by the surface pressure-area per molecule (π-A) isotherm measurement and the infrared reflection absorption spectroscopy (IRRAS). The corresponding Langmuir-Blodgett (LB) films were also investigated by the atomic force microscopy (AFM), the Fourier transform infrared spectroscopy (FT-IR), and the circular dichroism spectroscopy (CD). The π-A isotherms and AFM images reveal that the spacer of gemini surfactant has a significant effect on the surface properties of the complex monolayers. As s ≤ 6, the gemini/ds-DNA complex monolayers can both laterally and normally aggregate to form fibril structures with heights of 2.0-7.0 nm and widths of from several tens to ~300 nm. As s > 6, they can laterally condense to form the platform structure with about 1.4 nm height. Nevertheless, FT-IR, IRRAS, and CD spectra, as well as AFM images, suggest that DNA retains its double-stranded character when complexed. This is very important and meaningful for gene therapy because it is crucial to maintain the extracellular genes undamaged to obtain a high transfection efficiency. In addition, when s ≤ 6, the gemini/ds-DNA complex monolayers can experience a transition of DNA molecule from the double-stranded helical structure to a typical ψ-phase with a supramolecular chiral order.     

Geometrical shape of micelles formed by cationic dimeric surfactants determined with small-angle neutron scattering

The influence of spacer group on the geometrical shape of micelles formed by quaternary-bis dimeric (Gemini) surfactants C(12)H(25)N(CH(3))(2)(CH(2))(s)N(CH(3))(2)C(12)H(25) (12-s-12) has been investigated with small-angle neutron scattering (SANS). Dimeric surfactants with a short spacer unit (12-3-12 and 12-4-12) are observed to form elongated general ellipsoidal micelles with half axes a < b < c, whereas SANS data demonstrate that 12-s-12 surfactants with 6 ≤ s ≤ 12 form rather small spheroidal micelles rather than strictly spherical micelles. By means of comparing our present SANS results with previously determined growth rates using time-resolved fluorescence quenching, we are able to conclude that micelles formed by 12-6-12, 12-8-12, 12-10-12, and 12-12-12 are shaped as oblate rather than prolate spheroids. As a result, our present investigation suggests a never before reported structural behavior of Gemini surfactant micelles, according to which micelles transform from elongated ellipsoids to nonelongated oblate spheroids as the length of the spacer group is increased. The aggregation number of oblate micelles is observed to monotonously decrease with an increasing length of the surfactant spacer group, mainly as a result of a decreasing minor half axis (a), whereas the major half axis (b) is rather constant with respect to s. We argue that geometrically heterogeneous elongated micelles are formed by dimeric surfactants with a short spacer group mainly as a result of the surface charges becoming less uniformly distributed over the micelle interface. As the length of the spacer group increases, the distance between intramolecular charges become approximately equal to the average distance between charges on the micelle interface, and as a result, rather small oblate spheroidal micelles with a more uniform distribution of surface charges are formed by dimeric 12-s-12 surfactants with 6 ≤ s ≤ 12.     

Gemini surfactants at the air/water interface: a fully atomistic molecular dynamics study

Gemini surfactants typically consist of two single-chain surfactants chemically linked by a spacer molecule. We report herein the results of fully atomistic molecular dynamics (MD) simulations of a series of Gemini surfactants: CsH2s-alpha,omega-bis(C12H25N+(CH3)2Cl-), at the air/water interface with s = 3, 4, 6, 12, 14, and 16, at values of the initial surface area per surfactant AS = 70 A2, 77 A2, 95 A2, 151 A2, 133 A2, and 103 A2, respectively. The AS values employed were obtained from surface tension and neutron reflection experiments at the respective cmc of each surfactant. The Gemini surfactant corresponding to s = 3 was also simulated at AS = 105 A2, which is the experimentally derived value of surface area per surfactant at 1/10th of cmc. Only the surfactants with s = 12 and 14 and the surfactant with s = 3 at AS = 105 A2 gave a stable monolayer at the air/water interface. In other cases, we observe movement of some surfactant molecules from the air/water interface into the aqueous phase, resulting in a stable primary monolayer of surfactants at the air/water interface and a small concentration of surfactant molecules below it. The latter form aggregates, with their hydrophobic chains in the core. The density profiles along the normal to the interface are compared with the ones obtained from neutron reflection experiments. The MD simulations confirm the bending of the spacer toward the hydrophobic chains as the spacer length is increased and the spacer becomes more hydrophobic. The simulations have helped to shed light on the low-resolution picture which emerges from experimental analyses.     

Effect of the spacer length on the association and adsorption behavior of dissymmetric gemini surfactants

A series of dissymmetric gemini surfactants with the general formula [C12H25(CH3)2N(CH2)sN(CH3)2C14H29]Br2 designed as 12-s-14, where s=2, 6, and 10, were synthesized and their physicochemical properties investigated. The effect of spacer length on Krafft temperature, adsorption at the air/solution interface, and association in aqueous solution was studied by tensiometry, conductometry, and cryo-transmission electron microscopy. The Krafft temperature was found to increase linearly with spacer length. In the submicellar concentration range the dissymmetric 12-s-14 surfactants display ion pairing and premicellar association. Adsorption at air/solution interfaces and micellization in aqueous solution are similar to the behavior of their symmetric counterparts and depend strongly on spacer length.     

季铵盐型Gemini表面活性剂在金表面的吸附行为

以邻苯二酚(CC)为电化学探针, 利用循环伏安、交流阻抗等方法研究了不同阳离子Gemini表面活性剂(C16H33(CH3)2N-C4H8-N(CH3)2C16H33 (C16-C4-C16)、C12H25(CH3)2N-C4H8-N(CH3)2C12H25 (C12-C4-C12)、C8H17(CH3)2N-C4H8-N(CH3)2C8H17 (C8-C4-C8))在金电极表面的吸附性能. 结果表明, CC在KNO3溶液中可产生两对峰; 当向溶液中加入阳离子Gemini表面活性剂时, 第一对峰降低, 第二对峰升高, 峰电位差变大; 碳链长的表面活性剂对CC的氧化还原峰的影响较大. 同样, 碳链长的表面活性剂使电极界面的阻抗增大较多, 使石英晶片的频率变化较大. 根据CC的第一个氧化峰的面积随表面活性剂吸附的变化, 估测了它们的吸附模式. 发现这三种表面活性剂在金电极表面的吸附基本符合Langmuir吸附模型.     

The miscibility of poly(D,L-lactide-co-glycolide) with amphiphilic molecules and the interaction of their mixtures with DNA at air/water interface

The miscibility of poly(D,L-lactide-co-glycolide) (PLG) with three amphiphilic molecules and the interaction of the PLG/surfactant mixtures with DNA at air/water interface are investigated by pi-A isotherms, Brewster angle microscopy (BAM) and atomic force microscopy (AFM) techniques. The pi-A isotherms of the PLG mixtures with cationic C(12)AzoC(6)PyBr, and C(12)AzoC(6)N(CH(3))(3)Br, are quite different from the pi-A isotherm of pure PLG on water subphase. In contrast to the case, the pi-A isotherm of PLG mixed with nonionic C(12)AzoC(6)OPy is almost identical to the pure PLG except some increasing of molecular area. Similar phenomena are observed on DNA subphase. The in situ BAM and ex situ AFM observations demonstrate that the dispersion of PLG at air/water interface becomes good when it mixes with the two cationic surfactants, whereas quite poor due to the phase separation when it mixes with the nonionic amphiphilic molecule. Based on these results we conclude that the cationic surfactants can affect the conformation change of PLG at air/water interface and figure a well miscibility with polymer whereas the nonionic amphiphilic molecule presents poor miscibility. In addition, the even mixing of the PLG and the cationic surfactants is favorable for the adsorption to DNA more effectively.     

1H NMR study on pre-micellization of quaternary ammonium gemini surfactants

Two quaternary ammonium Gemini surfactant series, 12-s-12, ([C(12)H(25)N+ (CH(3))(2)](2)(CH(2))(s).(2)Br(-)) and 14-s-14 ([C(14)H(29)N(+)(CH(3))(2)](2)(CH(2))(s).(2)Br(-)), where s = 2, 3, and 4, have been studied by the use of (1)H NMR in aqueous solution at concentrations below their critical micelle concentrations (CMC) at 25 degrees C. The appearance of a second set of peaks for the 14-s-14 series and the changes in chemical shifts, line widths, and line shapes of the 12-s-12 series with increasing concentration below the CMC are interpreted as evidence for the formation of premicelle aggregates (oligomers) that appear at approximately one-half their CMC values. Self-diffusion coefficients (D) and transverse relaxation times (T(2)) have also been detected and support the results obtained by (1)H NMR.     

季铵盐型双子表面活性剂与十八醇的混合单分子膜

研究了双子表面活性剂12-2-16和12-2-12分别与十八醇(C18H37OH)在空气-水界面上混合单分子膜的π-A等温线. 在相分离表面压以下, 比较了不同表面压下和不同混合比单分子膜的混合表面过剩自由能ΔGMexo, 分析了双子表面活性剂与脂肪醇在空气-水界面上混合膜中的相容性. 结果表明, 12-2-16与C18H37OH在所有混合摩尔比下随着表面压增高, 自由能增大. 12-2-12与C18H37OH混合膜体系的相容性取决于两者的混合比, ΔGMexo随所加入C18H37OH摩尔分数的增加逐渐增大, 从异种分子间净的吸引作用转变到相互排斥作用体系, 转变点为C18H37OH加入量的摩尔分数0.65. 当混合为热力学自发过程时, 增大表面压将有利于混合; 而对相互排斥体系, 增加表面压将使体系内异种分子之间的相互排斥作用更大.