二次谐波光谱和布鲁斯特角显微镜研究二棕榈酰磷脂酰胆碱和维生素B2的相互作用

二棕榈酰磷脂酰胆碱（DPPC）分子在气液界面上形成的Langmuir膜是一种重要的生物膜模拟体系,其手性结构及其与外来物质的相互作用一直是相关学科研究的前沿问题。维生素B₂（VB₂）是人体中一种重要的营养物质,它在代谢障碍引起的脂质沉积性类疾病中有大量的实例应用,经常在一些特殊的临床症状中有出乎意料的治疗奇效。目前,VB₂如何参与到膜上生物事件的过程和细胞乃至生命的作用过程中的研究报道较少,特别是VB₂分子与磷脂分子靶标的立体相互作用,其可能发生的手性分子识别现象会在许多生物事件中起着关键作用。综合二次谐波-线二色光谱（SHG-LD）、Langmuir膜天平和布鲁斯特角显微镜(BAM)技术初步研究了VB₂和DPPC分子在气液界面上的相互作用,分别从气液界面上介观水平和宏观水平上互补表征脂质分子在气液界面上的分子骨架自组装的结构。压缩等温线发现纯水界面L-DPPC和D-DPPC液态扩展相/液态凝聚相(LE/LC)共存阶段的膜压几乎不变,race-DPPC的共存相膜压区域稍微缩短,VB₂水溶液界面上race-DPPC的LE/LC共存相消失。此外,弹性模量研究表明VB₂分子可以提高L-DPPC单分子层膜的弹性模量,但降低D-DPPC和race-DPPC单层膜的弹性模量。结合SHG-LD研究发现,在膜压13 mN·m-1下,L-DPPC在纯水和VB₂水溶液界面上表面手性过量值（DCE）保持不变。与纯水界面相比较,D-DPPC在VB₂水溶液上DCE值出现反转,而race-DPPC的DCE值则不随亚相改变而变化。相同膜压下,BAM观察到单一手性相互作用使得L-DPPC和D-DPPC在纯水界面上各自组装成不同枝臂弯曲方向的手性三叶草微畴(microdomain)。VB₂诱导D-DPPC微畴,使其直径增大1～2倍。同时,VB₂也诱导了race-DPPC单层膜上近似圆形状的微畴伸展,并长出了三条有曲率的枝臂。对此可以解释为VB₂降低了非单一手性相互作用的能量,使得race-DPPC出现手性相分离。与此同时,VB₂也诱导了race-DPPC单层膜微畴的手性结构发生变化。该研究有助于理解VB₂调节磷脂膜横向组织结构的分子机理,在细胞膜界面发生的过程中,脂层单层的二维特性和生物分子之间的相互作用可能决定了生物分子的亲和力。     

以非手性铕化合物为探针的手性氨基醇圆偏振荧光光谱

圆偏振荧光光谱(Circularly Polarized Luminescence,CPL)是一种手性化合物表征与分析的光谱手段,然而,直接CPL检测只适用于具有特征发色团的手性化合物,这极大限制了CPL的应用范围。本文报道了一种利用非手性荧光探针分子间接检测分子手性的CPL方法。以手性氨基醇的检测为例,研究发现:非手性铕化合物Eu(fod)3探针分子可与手性氨基醇相互作用,并使得Eu(fod)3产生诱导CPL(Induced circularly polarized luminescence,ICPL)信号,该ICPL信号不仅具有较高的不对称因子glum,而且其正负性与待测手性氨基醇的手性构型表现出极大的相关性。同时,研究发现ICPL光谱的glum值对不同结构的手性氨基醇表现出不同的变化趋势。以上结果表明以非手性铕化合物Eu(fod)3为探针分子的间接CPL检测方法是手性氨基醇类分子手性构型检测的有效手段。     

Cu(100)表面CO分子单层膜的原子结构

利用第一性原理研究了覆盖度分别为1.00, 0.50和0.25 ML时CO分子单层膜在Cu(100)表面的吸附系统. 计算表明CO分子对不稳定. 获得了CO分子单层膜在虚拟Cu(100)表面的原子结构, 以及CO分子单层膜在Cu(100)表面吸附系统的原子结构. 当CO分子单层膜在Cu(100)表面的三个吸附位吸附, 覆盖度为1.00 ML时, 顶位和桥位都稳定, 而空心位不稳定; 覆盖度为0.50和0.25 ML时, 三个吸附位都稳定.比较吸附前后CO分子单层膜的原子结构, 可知CO分子和Cu(100)表面的相互作用强于CO分子单层膜之间的相互作用. 关键词： CO分子单层膜 自组装 CASTEP Cu(100)     

Rh(111)表面NO分子对多层膜的原子结构

利用第一性原理研究了NO分子对[(NO)_2]分子链、分子单层膜,Rh(111)表面上的(NO)_2分子单层膜和多层膜的原子结构.(NO)_2分子单体在虚拟Rh(111)表面自组装成两个稳定的分子链,(NO)_2分子平行有序排列,氧原子和氮原子都呈现(100)和(111)结构.在虚拟Rh(111)-(1×3~(1/2))上,1.00 ML(molecular layer)覆盖度时,(NO)_2分子自组装成两个稳定的分子单层膜(M1和M2),分子膜M1中N-N键与衬底的夹角为70°-90°;分子膜M2中N-N键平行衬底.在M2/Rh(111)中,(NO)_2分子可吸附于顶位、fcc空心位和hcp空心位,通过电荷转移可解释两个空心位的稳定性强于顶位.Rh(111)表面(NO)_2分子多层膜系统中,(NO)_2分子垂直吸附于两个空心位,第一层是分子膜M2,N-N键平行于衬底,第二层及以上都是分子膜M1,N-N键与衬底夹角为70°-90°,分子膜真空层为0.31 nm±0.02 nm.     

气液界面超分子手性分布的原位二次谐波研究

界面超分子手性因其在材料、催化、生物等领域的应用前景得到了人们的广泛关注。卟啉(porphyrin)衍生物因具有强的π-π堆垛能力、生物兼容性和出色的电子性能,常用于构建界面超分子结构。卟啉衍生物的表面超分子手性研究多数在固体基底上进行。利用二次谐波线二色谱方法分析卟啉衍生物在空气/水界面形成的超分子结构,通过界面层不同位置处产生的S偏振二次谐波强度随入射基频光偏振态的变化研究界面超分子结构的手性分布。实验表明,卟啉衍生物TPPS吸附在两亲分子CTAB在空气/水界面上形成的单层后会形成超分子结构,该结构具有手性,且手性的二维分布是非均匀的。     

卵黄鞘磷脂与DOPC相互作用的单层膜

通过分析单层膜在固定表面压力下的过量分子面积和固定分子面积时的过量表面压力研究了卵黄鞘磷脂和1,2-二油酸基磷脂酰胆碱在单层膜中的混合性行为,通过分析过量吉布斯能量、过量亥姆霍兹能量和弹性系数评估了混合脂单层膜稳定性和压缩性. 热力学分析表明,相对于两组分理想混合时过量分子面积和过量表面压力呈现出正偏差,表明分子间的相互作用力为排斥力. 能量极值点出现在卵黄鞘磷脂含量为0.6处,表明该比例下单层膜结构状态不稳定. 排斥力诱导了单层膜中产生相分离.     

硒杂环化合物(4,5-苯并苤硒脑)在金表面上的自组装

为了寻求新的自组装单分子膜体系 ,构建新的功能膜 ,研究了具备平面型的大环共轭硒杂环化合物——— 4,5 苯并苤硒脑 (苯并 [c]硒二唑 ,简称苤硒脑 )在金表面的自组装单分子膜 .通过X射线光电子能谱 (XPS)和电化学手段对其进行表征 .XPS研究结果表明 ,自组装形成单分子膜后 ,苤硒脑分子中Se3d结合能从 5 7.4eV下降到 5 7.1eV ;表明硒杂环化合物是通过金硒键固定在金表面上的 ;电化学循环伏安法实验表明 ,金电极表面上自组装该有机硒后 ,Fe(CN) 63 -/ 4 -的氧化还原峰几乎完全消失 ;以四硼酸钠为底液 ,测得该化合物自组装在金表面上时 ,其还原电位在 - 0 .6 6V ,与在溶液中用裸金电极测得的还原峰电位基本一致 .     

用表面二次谐波检测L—B单分子膜层的聚合

本文首次报道用光学二次谐波实验检测L-B膜分子单层的聚合.膜层的非线性极化率的改变可用原子基团和价键理论解释.实验结果还提示,紧邻于表面的那层单体分子层的聚合先于其它原分子层.     

有机单分子层膜的介电常数理论研究

采用取向序参数计算了考虑分子固有偶极矩负电荷中心与分子卯定端不一致以及在一定区域内电偶极子不能视为点偶极子情况下,基底表面上有机单层膜的介电常数.计算结果表明单层膜的介电常数大小依赖于其基底物质的介电常数和分子负电荷中心离基底的距离.     

有机单分子层膜的介电常数理论研究

采用取向序参数计算了考虑分子固有偶极矩负电荷中心与分子卯定端不一致以及在一定区域内电偶极子不能视为点偶极子情况下，基底表面上有机单层膜的介电常数。计算结果表明单层膜的介电常数大小依赖于其基底物质的介电常数和分子负电荷中心离基底的距离。     

酞菁铜固态薄膜的红外光谱

利用红外透射光谱，偏振透射光谱、掠角反射光谱研究了三－２，４－二特戊基苯氧基８－喹啉氧基酞菁铜ＬＢ膜和蒸镀膜的结构。确认在ＬＢ膜中，（１）取代基的碳链是以六方晶系或假六方晶系方式堆积的；（２）用偏振红外可以区别苯环上的两个ＣＨ２的伸缩振动带。在蒸镀膜中分子基本呈现无序状态。     

Fourier Transform Infrared Spectroscopic Investigation on Langmuir-Blodgett Films of Octadecanoyl Ester of 1-(2-Carboxyethyl) Thymine: Molecular Orientation,Molecular Recognition to Complementary Base of Nucleic Acid and Order-Disorder Transition

Fourier transform infrared (FTIR) transmission, polarized transmission, reflection absorption (RA) and Attenuated total reflection (ATR) spectroscopy were employed to investigate the molecular orientation and molecular recognition to the complementary base at the air / water interface of a novel nucleolipid amphiphile, octadecanoyl ester of 1-(2-carboxyethyl) thymine. It has been found that the molecules are biaxially oriented and the hydrocarbon chain titled considerably from the substrate normal as well as the chromophoric part in the LB film Molecular recognition through complementary bases pairing takes place at the air / water interface between the thymine moiety in the head group of the amphiphile and adenosine in the subphase, the hydrogen involved in the host-guest interactions has been detected by using FTIR-ATR technique. FTIR transmission spectra measured at elevated temperatures revealed that the order-disorder transition of the LB film which contains the complementary base occurs at lower temperature. To our best knowledge, investigation of the order-disorder transitions in nucleolipid amphiphile LB films and comparative studies of the order-disorder transitions between nucleolipid amphiphile LB film that contains and does not contain the complementary bases have been virtually nonexistent, so far.     

Langmuir and Langmuir-Blodgett (LB) films of tetrapyridyl metalloporphyrins

We report on the formation of Langmuir films of 5,10,15,20-tetra(4-pyridyl) 21H,23H-porphine, hereafter named tetrapyridyl porphyrins with distinct central ions (2H⁺, Zn²⁺, Cu²⁺, Ni²⁺). The films were characterized with surface pressure and surface potential isotherms and in situ UV-vis absorbance. The measurements indicated strong aggregation of porphyrin monomers at the air-water interface, with a red shift of the Soret band in comparison with the spectrum obtained from CHCl₃ solutions. The shift was larger for the non-substituted H₂TPyP, and depended on the metal ion. Significantly, aggregation occurred right after spreading of the Langmuir film, with no further shifts in the UV-vis spectra upon compression of the film, or even after transferring them onto solid substrates in the form of Langmuir-Blodgett (LB) films. The buildup of LB films from H₂TPyP and ZnTPyP was monitored with UV-vis spectroscopy, indicating an equal amount of material deposited in each deposition step. Using FTIR in the transmission and reflection modes, we inferred that the H₂TPyP molecules exhibit no preferential orientation in the LB films, while for ZnTPyP there is preferential orientation, with the porphyrin molecules anchored to the substrate by the lateral pyridyl groups.     

红外光谱研究聚硅氧烷侧链手性液晶及其单体的单层LB膜

一种聚硅氧烷侧链手性液晶P及其单体M的单层LB膜分别在11mN/m和8mN/m的表面压力下,从水汽界面成功地转移到在镀金玻璃片和氟化钙基片上。π-A曲线表明P及其单体M在水汽界面上单层膜的崩溃压力分别是35和11mN/m。红外透过和反射吸收光谱表明两者的生色团部分及烷基链部分倾斜排列在固体基片上,但其倾斜角不同。M比P有更大的倾斜角。同时,不论P或M其烷基链的轴向与芳香核部分的长轴方向并不重合。P的烷基链比M的烷基链更有序。     

十八胺LB膜吸附组装金纳米颗粒研究

制备了十八胺单层、多层LB膜及粒径为几个纳米的金纳米粒子。pH值小于10.3时十八胺带正电荷,将其置于金纳米溶胶(pH值10.3)中,带负电荷的金纳米粒子与带正电荷的十八胺之间通过静电作用,金纳米颗粒被成功地吸附组装到十八胺LB膜中,形成纳米薄膜。紫外-可见光谱、红外光谱及扫描电镜显示:金纳米颗粒通过这种方法能够很好的组装在十八胺LB膜上,且其组装层整齐有序,同时也受十八胺LB膜层数及组装时间的影响。     

Structure and Orientation of 1-Hydroxyl-5-Hexadecyloxy-Naphthalene LB Films Studied By UV-VIS and FTIR Spectroscopy

Ultraviolet-visible (UV-Vis), infrared transmission, and reflection absorption(RA) spectra have been measured for one-and multi-monolayer Langmuir-Blodgett(LB) films of C₁₆H₃₃30Naph(1,5)OH at various temperature to investigate dependencies of the aggregation and phase transitions on the number of monolayers. The UV-vis spectra of the LB films have revealed that the C₁₆H₃₃ONaph(1,5)OH forms aggregates in the LB film. From the temperature dependence of UV-vis absorption spectra, it is clear that the aggregate is gradual converted to monomer upto 80 °C. A comparison of the infrared transmission and RA spectra reveals that the hydrocarbon chains are tilted considerably in the LB film. As for the naphthalene ring part, the result suggest that the ring plane is oriented approximately perpendicular to the substrate surface. The Temperature dependence of infrared transmission spectra have been measured for 1-, 3-, and 11-monolayer LB films to investigate dependence of phase transitions on the number of monolayers. These observations show that the one-monolayer LB films does not have a clear order-disorder transition, while the three-and eleven-monolayer films have a phase transition near 60 °C. Therefore, it seems that the title angles of both the alkyl chain and chromophore part change largely concomitantly with the conversion from the aggregate to the monolayer.     

Molecular Orientation and Aggregation in the Langmuir-Blodgett Films of 4-[4′-(4″-Decyloxy Phenylazo) Naphthloxy] Butyl Trimethylammonium Dextran Sulfate Studied by Ultra-Violet and Infrared Spectroscopy

Infrared transmission, Reflectance-Absorption (RA) and Ultra-Violet (UV) spectra were measured for mono-and multi-layers Langmuir-Blodgett (LB) films of 4-[4′-(4″-decyIoxy phenylazo)naphthloxy] butyl trimethylammonium bromide formed with SDS to study the molecular orientation and aggregation. The results indicate that the compound do not aggregate in the LB films, and the alkyl tail is nearly perpendicular to the substrate surface and the chromorphore part adopts trans-zigzag conformation. These results also suggest that the molecular orientation and aggregation are not depend upon the number of monolayers The comparison of infrared transmission and RA spectra indicates that the hydrocarbon chain is nearly perpendicular to the substrate surface, but the two rings in the chromophore part are tilted considerably from the surface normal.     

Ftir Studies on LB Film of Amphiphile with Schiff Base as Headgroup and Its Copper Complex

Two different ways to form monolayers and LB films (surface film and subphase film) of the complex have been used, where a novel amphiphile containing Schiff base as a headgroup was used as a ligand. the monolayer behavior at the air/water interface was characterized by π-A isotherms and two-dimensional molecular orientation of alkyl chains in LB films and thermal stability were measured by polarized and variable temperature FTIR transmission spectra, indicating that the LB film of the novel amphiphile and its copper(II) complex are very stable as well as stearic acid. Because incorporating the metal ion into the monolayer makes it more condensed, thermal stability of the LB film was enhanced. as can be compared from their structure and properties, subphase films are superior to surface films.     

Langmuir-Blodgett and Langmuir-Schaefer films of poly(5-amino-1-naphthol) conjugated polymer

Langmuir-type films of poly(5-amino-1-naphthol) conductive polymer were formed at the air/water interface. The surface pressure versus molecular area isotherms of the polymeric layers showed a high tendency to aggregate and non-monomolecular behavior on the water surface. Langmuir-Blodgett (LB) and Langmuir-Schaefer (LS) procedures have been successfully used to transfer the Langmuir films of this polymer onto hydrophilic silicon substrates. Atomic force microscopy images showed that the films obtained by the LS method have much better quality than those obtained by the LB one. In particular, we have obtained uniform and smooth LS films covering practically all the substrate, while the LB films showed rather aggregated material, only partially covering the substrate.     

1-羟基-5-十二烷氧基-萘LB膜结构和取向的光谱研究

用红外透射,反射光谱及紫外可见吸收光谱方法研究了１－羟基－５－十二烷基－萘ＬＢ膜及溶液状态下的结构,分子取向。研究结果表明分子在溶液中主要是以单体形式存在;在ＬＢ膜中是以聚集体形式存在。