十八胺单分子膜的研究

通过测定在纯水和CdCl2 溶液亚相上十八胺单分子膜的平衡、循环π～A等温线及其动态弹性 ,发现在亚相中加入Cd2 + 可以使膜的液态相凝聚性增强 ,固态相凝聚性减弱 .液态的单分子膜在两种亚相上有较好的可回复性 ,而在固态膜中则不然 .这可归因于在水面上十八胺分子间可形成氢键 ,而在CdCl2 水溶液亚相上的十八胺则与Cd2 + 发生配位 ,形成了多配位络合物 ,两种情况下十八胺分子在高膜压区都会发生稳定的聚集 .静、动态弹性的比较表明 ,膜障的振动不利于十八胺分子与Cd2 + 间的配位作用     

邻苯二甲酰肼的表面增强拉曼光谱——观察到正常拉曼光谱中禁阻的谱峰及对吸附构型的解释

测定了邻苯二甲酰肼粉末样品在400～2800cm~(-1)范围内的激光拉曼光谱和红外光谱。比较谱图很容易看出呈现互补关系,该化合物固体状态应具有对称中心。邻苯二甲酰肼碱性溶液的表面增强拉曼谱图上出现了粉末拉曼谱上没有的1374cm~(-1)处很强的峰和其他峰。这可解释为:在固态时,邻苯二甲酰肼两个分子间通过氢键形成二聚体,属C_(2h)点群,只有g类振动表现出拉曼活性;而在溶液中,二聚体破坏掉,在荷正电银电极作用下,两个氮原子上的氢脱掉,分子通过两个氮原子吸附在电极上,呈1.4—二酚式结构,属C_(2v)点群,所有振动都是拉曼活性的,表现出很多固态样品拉曼谱上禁阻的峰。     

应用二维偏振红外与拉曼相关光谱研究反铁电液晶的分子结构

应用偏振红外、拉曼光谱研究了一种反铁电液晶化合物在78℃时,SCA 相中的烷基链、刚性核部分的构象、分子排布。用二维相关技术对所得到的偏振红外、拉曼光谱进行分析,把与手性碳相连的甲基的反对称及对称伸缩振动谱带同烷基链中的甲基伸缩振动谱带区分开,并发现在反铁电相中同时存在s-cis和s-trans两种构象。     

苯乙烯基吡啶类液晶化合物的分子结构及相变过程的光谱研究

通过本乙烯基吡啶和不同脂肪羧酸间的氢键作用构成液晶的方法具有合成路线灵活、简便、易于变化的特点,本文通过变温红外光谱对做为质子受体的苯乙烯基吡啶粉液晶化合物的分子结构和相变过程中分子排列的变化进行了研究,结果表明在液晶分子中象羰基这样的偶极矩较大的极性基团,对分子所处的相态分子间的相互排列比较敏感。在红外光谱中羰基伸缩振动的变化可以看作是液晶分子相态转变的标志。     

RDX在溶液相中振动能量传递的二维红外光谱

采用傅里叶变换红外光谱(FTIR)和飞秒二维红外光谱(2DIR),结合量子化学计算,研究了1,3,5-三硝基-1,3,5-三氮杂环己烷(RDX)分子在DMSO溶液相中的振动能量传递过程。FTIR光谱结果表明,溶液相中RDX分子不再是自由的CS对称性,NO_2反对称伸缩振动的IR吸收带部分重叠。此外,2DIR光谱的指纹特征显示RDX分子中三个NO_2基团之间存在较强的振动耦合,同时三个NO_2基团之间有分子内能量传递过程。     

N-磷酰化叉肽结构与NMR波谱

测定了N-磷酰化叉肽(2-5)在溶液中的NMR谱.发现它们具有非对映异位,分子无规卷曲及氢键相互作用.波谱分析表明,磷酰基的参与,主要影响其结合部位的氨基酸.由于肽平面的生成及分子内、分子间氢键影响的改变,致使叉肽中支链的Dipp-Ala磷酰基与β位羰基的相对位置发生变化.磷酰基与N-C_α基团仍处于反式位置,这可能是该氨基酸侧链无极性基团的缘故.     

氯化钙对尼龙6无定形转变过程的在位红外研究

采用在位红外分析、X射线衍射方法研究了氯化钙对尼龙 6结晶的影响。结果表明 ,随尼龙 6中氯化钙含量的增加 ,尼龙 6的结晶度逐渐减小直至变为无定形态。由于氢键作用使尼龙 6分子链规整排列产生结晶 ,因此文章通过在位红外光谱方法研究了尼龙 6 /氯化钙复合材料中与氢键相关的胺基、酰胺Ⅰ带和酰胺Ⅱ带随温度及氯化钙含量的变化情况 ,证实了钙离子能通过与尼龙 6分子链上的羰基发生配位作用 ,插入尼龙 6分子链 ,破坏尼龙 6的氢键 ,降低了尼龙 6分子链的规整排列 ,使尼龙 6的结晶度减小 ,最终使尼龙 6由结晶态转变为无定形态     

聚酰胺66溶液弛豫行为的NMR研究

用1D和2D NMR技术归属了聚酰胺66的1H和13C的NMR共振信号,并通过聚酰胺66溶液温度和浓度改变对氢核弛豫时间的影响,得到了其分子运动信息.结果表明随着温度的升高,聚酰胺66链间氢键逐渐解离,大分子链间相互作用逐渐减弱.而解离出来的链段又与溶剂小分子可以形成新的氢键,使聚酰胺66链卷曲并包含着部分溶剂分子一起运动.随着溶液浓度的增大,由于分子链间距变小,使得分子间作用力增强,链缠结程度加大,使链运动受限.     

脉冲升温纳秒时间分辨中红外光谱研究氨基酸重水溶液的分子间氢键

应用变温傅立叶变换红外光谱和脉冲升温纳秒时间分辨红外差谱研究了组氨酸和甘氨酸的重水溶液的羧基负离子的振动．结果表明不仅氨基酸分子之间形成氢键，而且氨基酸分子和溶剂分子之间也形成氢键．当温度升高时，羧基负离子在1600?1610 cm?1 附近的反对称伸缩振动发生蓝移，说明高温使氢键减弱．温度从10℃突然升高到20℃，组氨酸的时间分辨瞬态光谱出现两个漂白峰，一个在1604 cm?1，指认为形成氨基酸分子间氢键的羧基负离子的峰；另一个在1612 cm?1，指认为氨基酸分子和溶剂分子形成氢键的羧基负离子的峰．前     

绿色木霉纤维素酶分子内氢键特征的研究

运用能够揭示蛋白质分子基团振动特征的激光拉曼光谱分析技术，对绿色木霉纤维素酶中的CBHⅡ在固态以及两种pH值的液态中酶分子内的氢键状态进行了分析。结果表明相对于纤维素酶固体干粉，液态中酶分子酰胺Ⅰ羰基氧原子作为氢键质子受体的能力为上升；酰胺Ⅱ与酰胺Ⅰ的β结构特征峰变化倾向相似。在3种样品中，酶蛋白中Trp均为强氢键供体，从成键能力方面证实了以往同类酶空间分析的结果。固体与pH6．0水溶液酶蛋白中酪氨酸酚羟基成键能力也是强的。根据游离巯基分析可以判断绿色木霉CBHⅡ的成熟肽CBD与瑞氏木霉CBHⅡ的CBD有相似的二硫键构成。     

The effects of chain number and state of lipid derivatives of nucleosides on hydrogen bonding and self-assembly through the investigation of Langmuir-Blodgett films

The long-chain lipid derivatives of acyclovir—a nucleoside analogue were used to prepare Langmuir-Blodgett (LB) films, including the single-chained derivative (SGSA) and the double-chained derivative (DASA). The bilayer LB film of DASA or the SGSA/cholesterol (SGSA/Chol) mixture (1:1, mol/mol) on quartz plates was investigated with ultraviolet absorption spectroscopy, and the blue-shifted absorption with 4 nm (DASA) or 18 nm (SGSA/Chol) wavelength changes was observed in comparison with their solutions in chloroform. The rigid double chains of DASA prevented adjacent molecules from approach, while the flexible single chains of SGSA did not. Then the strength of intermolecular hydrogen bonding between the nucleoside moieties of DASA was much more weaker than one of SGSA, and their blue-shifted wavelength in LB films was different. DASA and SGSA/Chol also showed the different bilayer LB films on mica according to the atomic force microscopic observation. The former was prone to tilting on solid supports while the latter would like to stand vertically with the help of cholesterol that could insert into the flexible single chains of SGSA. The chain number (one or two) and state (flexible or rigid) of lipid derivatives of nucleosides strongly impact intermolecular hydrogen bonding and self-assembly behavior.     

拉曼光谱研究人参皂苷Rb1与DPPC双层膜的作用

为深入了解人参皂苷的分子药理学特性,阐明人参皂苷与细胞膜的作用机制,利用拉曼光谱从分子水平研究了不同浓度人参皂苷Rb1与DPPC(二棕榈酰磷脂酸胆碱)双层膜的作用.结果表明,人参皂苷Rb1没有改变DPPC的极性头部O-C-C-N+的稳定构象,极性头仍然平行于膜表面.并且,拉曼峰值比I1096/I1126/1096/I1062和I2848/I288/0随着药物浓度的增加而相应的变大,说明Rbl增加了烃链的无序度,增强了双层膜的流动性.由此推测该药物与DPPC的作用可能由于皂苷分子内及分子间的氢键与磷脂双层膜的极性头部相作用而停留在膜的表面.     

Vibrational Spectra of Benzylidene Aniline,O-Hydroxybenzylidene O-Hydroxyaniline and its Complexes with Cu(II) and NI(II) Metal Ions

Abstract

The FTIR and FT Raman spectra of benzylidene aniline, and o-hydroxybenzylidene o-hydroxyaniline compounds in the solid state in the wavenumber (1800-200 cm^?1) are recorded. An assignment for nearly all fundamentals are proposed. Comparison of the spectra of trans stilbene and benzylidene aniline reveals that v N-Ph stretch for the latter compound is situated at 1368 cm^?1 in the IR spectra with medium intensity. for o-hydroxybenzylidene o-hydroxyaniline, the stretching modes v N-Ph, and v C-Ph are observed at 1356 and 1226 cm^?1 respectively. the two v O-Ph are observed as intense bands in the IR spectra at 1245 and 1278 cm^?1, respectively. the FTIR spectra of the o-hydroxybenzylidene o-hydroxyaniline complexes with Cu(II) and Ni(II) metal ions are also recorded and assigned.     

两亲性光敏剂Al(OH)PcSP在醇水和水溶液中的分子光谱和存在状态

研究了具有光动力抗癌活性的两亲性光敏剂磺基邻苯二甲酰亚胺甲基酞菁羟基铝 (Al(OH)PcSP)在醇水和在水中的电子吸收光谱 ,并探讨了其聚集状态。研究表明 ,Al(OH)PcSP在醇水溶液中以单体形式存在 ,醇的碳链和羟基数对Al(OH)PcSP的单体吸收光谱没有显著的影响。但在水中 ,Al(OH)PcSP存在单体 二聚体平衡 ,二聚平衡常数为 5 730 7× 10 4 mol·L-1。Al(OH)PcSP在水中所形成的二聚体的Q带特征吸收峰位于 740 5nm ,相对于其单体特征吸收峰 (6 76 5nm)红移 ,而一般金属酞菁在水中所形成的聚集体Q带特征吸收光谱均相对于单体兰移至位于 6 30nm附近。研究了Al(OH)PcSP的荧光光谱 ,结果说明 ,二聚体的荧光很弱。     

New proton conducting materials for technical applications: what can we learn from solid state NMR studies?

Many novel proton conducting materials are based on complex hydrogen bonding networks of amphoteric hydrogen bonded moieties. Solid state NMR provides unique methods to study the properties of such network and specific proton conduction mechanisms in detail. In particular 1H solid state NMR techniques under fast magic angle spinning are powerful tools in this area. Site specific studies of the dynamic behavior via variable temperature 1H MAS measurements provide insight in the thermodynamics of the hydrogen bonding as well as activation energies for the proton transfer between the amphoteric sites. On macroscopic length scales, pulsed field gradient NMR experiments are able to determine the proton mobility and the contribution of different conduction mechanisms. In this article, aspects of recent solid state NMR studies in the field are reviewed and typical experimental methods as well as their possible outcome are discussed.     

Theory of Direct Photoisomerization of Stilbene

A microscopic model for describing the direct trans-cis photoisomerization of stilbene is developed and an interpretation of the experimental results found from time-resolved fluorescence and absorption spectroscopy of stilbene in solution is given. According to this model the photoisomerization of trans-stilbene is proposed to involve the radiationless transition from the trans singlet state S₁(trans), prepared by direct optical excitation, into the perp singlet state S₁ (perp) and the radiationless decay of this state into the quasi-isoenergetic trans triplet state T₄ (trans).     

Wetting of phospholipid membranes on hydrophilic surfaces - Concepts towards self-healing membranes

We report on the wetting behavior of phospholipid membranes on solid surfaces immersed in aqueous solution. Using fluorescence microscopy, the spreading velocity of fluid bilayers advancing from a lipid source is investigated. The kinetic spreading coefficient was measured as a function of temperature for pure DMPC membranes and as a function of charge density and cholesterol content for binary membranes. A theoretical model for the membrane flow is presented, which takes into account the liquid crystalline bilayer architecture of the lipid membrane. The spreading power results from the membrane-solid VdW interaction and is dissipated in hydrodynamic shear flow as well as by inter-monolayer friction within the bilayer. The frictional drag causes a dynamic tension gradient in the spreading membrane, which is manifested by a single exponential decay of the fluorescence intensity profile along the spreading direction. Obstacles are shown to act as pinning centers deforming the advancing line interface. However, no depinning was observed, since the centers are circumflown without abrupt relaxation. Received 6 November 1998     

2D solid state NMR spectral simulation of 3(10), alpha, and pi-helices

Transmembrane helices are more uniform in structure than similar helices in water soluble proteins. Solid state NMR of aligned bilayer samples is being increasingly used to characterize helical membrane protein structures. Traditional spectroscopic methods have difficulty distinguishing between helices with i to i + 3 (3(10)), i to i + 4 (alpha), and i to i + 5 (pi) hydrogen bonding topology. Here, we show that resonance patterns in PISEMA spectra simulated for these different helices show unique and striking features. The size and shape of these Polar Index Slant Angle (PISA) wheels, as well as the resonances per turn and clockwise versus counter-clockwise sequential connectivity of the resonances demonstrate how these different helical structures, if present as a uniform structure, will be readily distinguished, and characterized.     

2D solid state NMR spectral simulation of 310, α, and π-helices

Transmembrane helices are more uniform in structure than similar helices in water soluble proteins. Solid state NMR of aligned bilayer samples is being increasingly used to characterize helical membrane protein structures. Traditional spectroscopic methods have difficulty distinguishing between helices with i to i + 3 (3(10)), i to i + 4 (alpha), and i to i + 5 (pi) hydrogen bonding topology. Here, we show that resonance patterns in PISEMA spectra simulated for these different helices show unique and striking features. The size and shape of these Polar Index Slant Angle (PISA) wheels, as well as the resonances per turn and clockwise versus counter-clockwise sequential connectivity of the resonances demonstrate how these different helical structures, if present as a uniform structure, will be readily distinguished, and characterized.     

Study of Langmuir-Blodgett polydiacetylene polymer films by surface enhanced Raman scattering

Large shifts (～50 cm^-1) to lower energies in the C=C and C≡C stretching modes of the Raman spectra of Langmuir-Blodgett deposted thin films of 15-8 polydiacetylene polymer are observed as the film thickness changes from a monolayer or one bilayer to two or more bilayers. The spectra of two or more bilayers are found to be identical to bulk material. These large shifts, observed by surface enhanced Raman scattering from the silver island substrate on which the films are deposited are attributed to delocalization of the electronic states in the backbone of the polydiacetylene polymer.