亚相pH对气水界面上VE/DPPC单分子膜的影响

通过表面压－分子面积等温线的测定，考察了亚相ｐＨ对气水界面上的维生素Ｅ（ＶＥ）／二棕榈酰基磷脂酰胆碱单分子膜的影响。亚相ｐＨ降低不改变ＤＰＰＣ单分子膜的崩裂压，但使ＶＥ单分子膜的崩裂压明显增大，不改变ＶＥ单分子膜的平均分子面积，但使ＤＰＰＣ单分子膜凝缩，低表面压下，ＶＥ对ＤＰＰＣ单分子膜的膨胀作用在纯水上很小，在ｐＨ为１的亚相上则很明显，这提示在低ｐＨ的亚相上，ＶＥ／ＤＰＰＣ单分子膜中的极性头基间     

STUDY ON IN SITU LASER-INDUCED FLUORESCENCE SPECTROELECTROCHEMISTRY OF α,β

ＳＴＵＤＹＯＮＩＮＳＩＴＵＬＡＳＥＲ－ＩＮＤＵＣＥＤＦＬＵＯＲＥＳＣＥＮＣＥＳＰＥＣＴＲＯＥＬＥＣＴＲＯＣＨＥＭＩＳＴＲＹＯＦα，β，γ，δ－ＴＥＴＲＡ（４－ＴＲＩＭＥＴＨＹＬＡＭＭＯＮＩＵＭＰＨＥＮＹＬ）ＰＯＲＰＨＹＲＩＮ￥ＱｉａｎｇＨＵ；ＪｉＭｉ...     

磷钼酸催化合成DL—α—生育酚

以磷钼酸（Ｈ３ＰＭｏ１２Ｏ４０）为催化剂,通过２,３,５－三怪醌与异植醇在室温下缩合得到ＤＬ－α－生育酚（维生素Ｅ）,发现Ｈ３ＰＭｏ１２Ｏ４０是合成ＤＬ－α－生育酚的一种高活性、易于分离和能够重复使用的催化剂。     

胆甾液晶二氮杂冠醚—Eu（Ⅲ）配合物LB膜和荧光性质研究

研究了胆甾液晶二氮杂冠醚Ｎ，Ｎ′－双（胆甾－５－烯－３β－氧羰甲基）－１，１０－二氮－４，７，１３，１６－四氧环十八烷（１）及其与Ｅｕ＾３＋的配合物（２），２一苯甲酸的混配物（３）的ＬＢ膜和荧光性质，结果表明：１，２和３在水溶液亚相液面形成稳定的单分子膜，但只有１的单分子面积受亚相ｐＨ的影响１，２和３的单分子膜都容易转移到石英基片上形成ＬＢ膜，其中２和３为Ｘ型，转移比分别为０．６和１．０，在ＬＢ膜     

LB膜技术对葡萄糖氧化酶分子构象的影响

利用π－Ａ曲线、布儒斯特角显微镜（ＢＡＭ）及ＣＤ光谱对葡萄糖氧化酶（ＧＯＤ）的甲醇溶液铺展在ＣｄＣｌ２水溶液和纯水表面上形成的单分子膜进行了研究，以了解ＧＯＤ分子的自组和折叠情况，发现甲醇或者ＣｄＣｌ２都能ＧＯＤ分子更加疏水，易形成单分子膜，铺展在ＣｄＣｌ２溶液上比铺展在纯水上更加能使ＧＯＤ的单分子膜排列紧密，在表面压较高时，能观察到形成了第二层膜，并且使ＧＯＤ分子的构象从β－折叠片向α－螺旋转变     

镧系双2:17钨磷杂多配合物异构体的合成和性质研究Ⅲ

本文合成通式为（ＮＨ４）１７［Ｌｎ（α２－Ｐ２Ｗ１７Ｏ６１）２］．ｘＨ２Ｏ（Ｌｎ＝Ｌａ，Ｃｅ，Ｐｒ，Ｎｄ，Ｓｍ，Ｅｕ，Ｇｄ，Ｄｙ）的镧系双２：１７钨磷杂多配合物纯净异构体。并用＾３＾１ＰＮＭＲ，ＩＲ，ＵＶ－Ｖｉｓ吸收光谱，极谱，循环伏安和磁化率等对其进行了表征。对α１，α２和β异构体间的性质进行了比较。 α２异构体的Ｌ ｎ－Ｏ键离子特性强于α１异构体。     

C60在卟啉衍生物Langmuir单层膜中的分散状态

研究了Ｃ６０在四苯基卟啉衍生物５，１０，１５，２０－四－对（癸酸α氧基）苯基卟啉（ＴＤＰＰ）及５，１０，１５，２０－四－对（乙酸α氧基）苯基卟啉（ＴＡＰＰ）单层膜中的分散状态。空气／Ｃｄ＾２＋水溶液界面上混合单层膜的π－Ａ等温线、混合膜与花生酸（ＡＡ）形成的交替多层膜的低角Ｘ射线衍射实验及混合单层ＬＢ膜的ＵＶ－Ｖｉｓ光谱表明，在ＴＤＰＰ／Ｃ６０（１：１）的混合单层膜中，Ｃ６０以单分子或（和）聚集体     

脱氧核糖核酸变性和损伤的吸附伏安法研究

本文用汞电极（ＨＭＤＥ）二次导数阴极吸附伏安（ＳＤ－ＡｄＣＳＶ）和碳电极（ＧＣＥ、ＣＰＥ）导数循环伏安（ＦＤ－ＣＶ）法研究了核酸受热、紫外线、超声波和丝裂霉素Ｃ（ＭＭＣ）作用下的变性作用。在０．１ｍｏｌ／Ｌ（Ｋ２ＨＰＯ４＋ＫＨ２ＰＯ４）－０．１ｍｏｌ．Ｌ ＮａＣｌ（ｐＨ７．０）底液中，吸附的单股（ｓｓ－）和双螺旋（ｄｓ－）ＤＮＡ分别在ＨＭＤＥ上得到特征还原峰Ｐ３和Ｐ２，和在碳电极上得到氧化峰Ａ。物     

水杨醛－L－甲硫氨酸希夫碱钴（Ⅱ）配合物的热分解动力学

本文合成了一种新的希夫碱配合物，水杨醛－Ｌ－甲硫氨酸—水合钴（Ⅱ），Ｃｏ（ｓａｌｍｅｔ）·Ｈ２Ｏ，并用非等温热重法研究了它的热分解反应动力学。ＴＧ及ＤＴＧ曲线表明配合物按两步分解：Ｃｏ（ｓａｌｍｅｔ）·Ｈ２Ｏ１４２－１７５℃（１）→Ｃｏ（ｓａｌｍｅｔ）１７５－８２０℃（２）→ＣｏＯ用Ａｒｃｈａｒ微分法和Ｃｏａｔｓ－Ｒｅｄｆｅｒｎ积分法联合求出两步骤的动力学。步骤（１）、（２）的动力学方程分别表示如下：ｄα／ｄｔ＝Ａ·ｅ－Ｅ／ＲＴ（１－α）［－ｌｎ（１－α）］ｄα／ｄｔ＝Ａ·ｅ－Ｅ／ＲＴ（１－α）２［（１－α）－１－１］     

萃取法研究混配配合物中配体间的芳环堆积作用Ⅲ．Cu2＋－phen－PCA－体系

用萃取法研究Ｃｕ２＋－ｐｈｅｎ－ＰＣＡ－体系中配体间的芳环堆积作用（ｐｈｅｎ＝１，１０－邻菲罗啉，ＰＣＡ－＝苯甲酸根（Ｂｚ－）、α－苯乙酸根（ＰＡｃ－）、β－苯丙酸根（ＰＰｒ－）和γ－苯丁酸根（ＰＢｕ－），结果表明，配合物中芳环堆积作用依赖于ＰＣＡ－中苯环与羧酸根间碳链的长度，其顺序为：Ｂｚ－＜ＰＡｃ－＜ＰＰｒ－＜ＰＢｕ－。     

Membrane properties of binary and ternary systems of ganglioside GM1/dipalmitoylphosphatidylcholine/dioleoylphosphatidylcholine

The membrane properties of the ganglioside GM1 (GM1)/dioleoylphosphatidylcholine (DOPC) binary system and GM1/dipalmitoylphosphatidylcholine (DPPC)/DOPC ternary system were investigated using surface pressure measurements and atomic force microscopy (AFM), and the effect of surface pressure on the properties of the membranes was examined. Mixed GM1/DPPC/DOPC monolayers were deposited on mica using the Langmuir-Blodgett technique for AFM. GM1 and DOPC were immiscible and phase-separated. The AFM image of the GM1/DOPC (1:1) monolayer showed island-like GM1 domains embedded in the DOPC matrix. There was no morphological change on varying surface pressure. The surface pressure-area isotherm of the GM1/DPPC/DOPC (2:9:9) monolayer showed a two-step collapse as in the DPPC/DOPC (1:1) monolayer. The AFM image for the GM1/DPPC/DOPC monolayer showed DPPC and GM1 domains in the DOPC matrix, and the DPPC-rich phase containing GM1 showed a percolation pattern the same as the GM1/DPPC (1:9) monolayer. The percolation pattern in the GM1/DPPC/DOPC monolayer changed as the surface pressure was varied. The surface pressure-responsive change in morphology of GM1 was affected by the surrounding environment, suggesting that the GM1 localized in each organ has a specific role.     

Atomic force microscopy studies of ganglioside GM1alpha in dioleoylphosphatidylcholine/dipalmitoylphosphatidylcholine mixed monolayers and hybrid bilayers

The membrane states of the alpha-series ganglioside GM1alpha in 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC)/1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) mixed monolayers and hybrid bilayers were investigated using atomic force microscopy (AFM). The AFM image for the GM1alpha/DOPC/DPPC ternary monolayers showed the formation of GM1alpha-raft in the DOPC matrix. As increase of the surface pressure, GM1alpha are condensed in DPPC-rich domains; long and slender GM1alpha-rafts are separated from the DPPC-rich domains into the DOPC matrix. The GM1alpha/DOPC/DPPC ternary monolayers were deposited on mica coated with the first layer (1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine: DPPE) using the Langmuir-Schaeffer technique. The AFM image for the hybrid bilayers showed that same molecules were heterogeneously concentrated according to increase of the surface pressure to form GM1alpha-raft, DPPC-rich domain and DOPC matrix, being in agreement with the observation on the monolayer experiment. The found phenomenon implies that a binding of lectin to GM1alpha causes the increase of the surface pressure, the localization of GM1alpha and the succeeding formation of the raft as a first step of a specific signal transduction.     

DOPC/DPPC单层膜中分子间的相互作用及形态特征

利用Langmuir-Blodgett(LB)技术制备了不同表面压力下的1,2-二油酸-甘油-3-磷脂酰胆碱(DOPC)/1,2-二棕榈酸甘油-3-磷脂酰胆碱(DPPC)(摩尔比为1:1)和DOPC/DPPC/Chol(摩尔比为2:2:1)单层膜, 对单层膜内分子间的相互作用进行了热力学分析, 并用荧光显微镜和原子力显微镜对其形态进行了观测.热力学分析表明, DOPC与DPPC分子在单层膜结构中相互作用为排斥力, 诱导单层膜出现相变; DOPC, DPPC与胆固醇(Chol)间的相互作用均为吸引力, 当表面压力(π)大于18 mN/m时, DPPC与胆固醇的作用力大于DOPC.荧光显微镜观测表明, DOPC/DPPC单层膜出现明显相分离现象, 富含DPPC微区成“花形”结构, 且随着表面压力的升高微区逐渐增大, “花瓣”增多; 当胆固醇加入到DOPC/DPPC体系时, 单层膜相态由液相与凝胶相共存转变为液态无序相与液态有序相共存结构, 富含DPPC的微区形状从“花形”转变成“圆形”.原子力显微镜对单层膜的表征验证了荧光显微镜的观测结果, 表明胆固醇加入到DOPC/DPPC体系中对单层膜排列具有明显的影响, 压力和溶液状态等是影响脂膜结构的重要因素.     

Effect of membrane composition on surface states of ganglioside GM1/dipalmitoylphosphatidylcholine/dioleoylphosphatidylcholine monolayers

The surface states of ganglioside GM1 (GM1)/dipalmitoylphosphatidylcholine (DPPC)/dioleoylphosphatidylcholine (DOPC) monolayers having various compositions were investigated using atomic force microscopy (AFM), and the effect of the composition on the surface states of the membrane was examined. The AFM images for the ternary system showed a DPPC-rich phase containing GM1 in the DOPC matrix, which indicated that the morphology varied as the composition of the monolayers changed. The AFM images for the GM1/DPPC/DOPC monolayers having (2:9:9) and (4:18:9) molar ratios showed a percolation pattern similar to that observed for the GM1/DPPC (1:9) monolayer. The AFM image for the GM1/DPPC/DOPC (2:18:9) monolayer showed a dotted pattern with a high topography. Monolayers having a higher content of DOPC than DPPC and/or having a higher content of GM1 showed dot-like domains in the DPPC-rich phase containing GM1. In conclusion, the surface states of GM1/DPPC/DOPC monolayers changed depending on the composition. These results may be related to a diversity of GM1 in various organs.     

Effect of hydrocarbon chain and pH on structural and topographical characteristics of phospholipid monolayers

Structural characteristics (structure, elasticity, topography, and film thickness) of dipalmitoyl phosphatidylcholine (DPPC) and dioleoyl phosphatidylcholine (DOPC) monolayers were determined at the air-water interface at 20 degrees C and pH values of 5, 7, and 9 by means of surface pressure (pi)-area (A) isotherms combined with Brewster angle microscopy (BAM) and atomic force microscopy (AFM). From the pi-A isotherms and the monolayer elasticity, we deduced that, during compression, DPPC monolayers present a structural polymorphism at the air-water interface, with the homogeneous liquid-expanded (LE) structure; the liquid-condensed structure (LC) showing film anisotropy and DPPC domains with heterogeneous structures; and, finally, a homogeneous structure when the close-packed film molecules were in the solid (S) structure at higher surface pressures. However, DOPC monolayers had a liquid-expanded (LE) structure under all experimental conditions, a consequence of weak molecular interactions because of the double bond of the hydrocarbon chain. DPPC and DOPC monolayer structures are practically the same at pH values of 5 and 7, but a more expanded structure in the monolayer with a lower elasticity was observed at pH 9. BAM and AFM images corroborate, at the microscopic and nanoscopic levels, respectively, the same structural polymorphism deduced from the pi-A isotherm for DPPC and the homogeneous structure for DOPC monolayers as a function of surface pressure and the aqueous-phase pH. The results also corroborate that the structural characteristics and topography of phospholipids (DPPC and DOPC) are highly dependent on the presence of a double bond in the hydrocarbon chain.     

Mode of interaction of amphiphilic alpha-helical peptide with phosphatidylcholines at the air-water interface

Surface pressure (pi)-, surface potential (deltaV)-, and dipole moment (mu(perpendicular))-area (A) isotherms and morphological behavior were examined for monolayers of a newly designed 18-mer amphiphilic alpha-helical peptide (Hel 13-5), DPPC, and DPPC/egg-PC (1:1) and their combinations by the Wilhelmy method, ionizing electrode method, fluorescence microscopy (FM), and atomic force microscopy (AFM). The newly designed Hel 13-5 showed rapid adsorption into the air-liquid interface to form interfacial films such as a SP-B function. Regardless of the composition and constituents in their multicomponent system of DPPC/egg-PC, the collapse pressure (pi(c); approximately 42 mN m(-1)) was constant, implying that Hel 13-5 with the fluid composition of egg-PC is squeezed out of Hel 13-5/DPPC/egg-PC monolayers accompanying a two- to three-dimensional phase transformation. FM showed that adding a small amount of Hel 13-5 to DPPC induced a dispersed pattern of ordered domains with a "moth-eaten" appearance, whereas shrinkage of ordered domains in size occurred for the DPPC/egg-PC mixture with Hel 13-5. Furthermore, AFM indicated that (i) the intermediate phase was formed in pure Hel 13-5 systems between monolayer states and excluded nanoparticles, (ii) protrusions necessarily located on DPPC monolayers, and (iii) beyond the collapse pressure of Hel 13-5, Hel 13-5 was squeezed out of the system into the aqueous subphase. Furthermore, hysteresis curves of these systems nicely resemble those of the DPPC/SP-B and DPPC/SP-C mixtures reported before.     

Thermodynamic characterization of the prevailing molecular interactions in mixed floating monolayers of phospholipids and usnic acid

The investigation of the characteristics of mixed floating monolayers of phospholipids and usnic acid (UA), an active metabolite from lichens, can provide valuable information on how to prepare stable liposomes that could serve as carriers of UA for therapeutic proposes. The present paper is concerned with the thermodynamic analysis of the behavior of Langmuir monolayers formed by mixing different phospholipids (dibehenoylphosphatidylcholine, DBPC, dipalmitoylphosphatidylcholine, DPPC, and dioleoylphosphatidylcholine, DOPC) and UA at varied molar fractions. Relevant thermodynamic parameters such as excess areas, excess free energies and free energy of mixing were derived from the surface pressure data obtained from compression measurements performed in a Langmuir trough. For the largest lateral pressure examined (25 mN/m), negative values of the excess free energy were found only for the DOPC/UA monolayer, which should be the most stable of them. Based on the calculated values of the free energy of mixing, we note that the DBPC/UA and DPPC/UA systems present the best mixed character at low pressures and when the molar fraction of the UA is 0.5; at that relative concentration and at low values of the external pressure, the UA molecules can better mix and interact with the phospholipid molecules. The compression isotherms for mixed monolayers show no visible transitions, exhibiting a more organized phase that corresponds to a negative free energy of mixing. We have established that the most stable monolayers were those corresponding to DOPC/UA mixtures with a UA molar fraction of 0.75.     

Relaxation phenomena in phospholipid monolayers at the air–water interface

In this work we are concerned with the study of long-term relaxation phenomena in dipalmitoyl phosphatidylcholine (DPPC) and dioleoyl phosphatidylcholine (DOPC) monolayers spread at the air–water interface as a function of the surface pressure and the aqueous phase pH (pH 5, 7, and 9). Long-term relaxation phenomena were determined in an automated Langmuir-type film balance at constant temperature (20 °C). Two kinds of experiments were performed to analyze relaxation mechanisms. In one, the surface pressure (π) was kept constant, and the area (A) was measured as a function of time (θ). In the second, the area was kept constant at monolayer collapse and the surface pressure was decreased. This decrease was measured as a function of time. Various relaxation mechanisms, including monolayer molecular loss by dissolution, collapse, and/or organization/reorganization changes, can be fitted to the results derived from these experiments. These relaxation mechanisms are pH and phospholipid dependent. In the discussion, special attention will be given to the effect of the relaxation phenomena on the hysteresis in π–A isotherms before and after the relaxation experiment. At π lower than the equilibrium spreading pressure (π_e) the relaxation phenomena are mainly due to the loss of DPPC or DOPC molecules by desorption into the bulk aqueous phase. The formation of interfacial macroscopic vesicles, which are dissolved into the bulk phase, makes the phospholipid monolayer molecular loss irreversible. At the collapse point (at π > π_e), the relaxation phenomena may be due either to collapse for DPPC and/or to a complex mechanism including competition between desorption and monolayer collapse for DOPC.     

On the interaction of dipalmitoyl phosphatidylcholine with normal long-chain alcohols in a mixed monolayer: a thermodynamic study

This study investigated the mixed monolayer behavior of dipalmitoyl phosphatidylcholine (DPPC) with normal long-chain alcohols at the air/water interface. Surface pressure–area isotherms of mixed DPPC/C₁₈OH and DPPC/C₂₀OH monolayers at 37°C were obtained and compared with previous results for the mixed DPPC/C₁₆OH system. The negative deviations from additivity of the areas and the variation of the collapse pressure with composition imply that DPPC and long-chain alcohols were miscible and formed non-ideal monolayers at the interface. At lower surface pressures, it seems that the attractive intermolecular force was dominant in molecular packing in the mixed monolayers. At higher surface pressures, the data suggest that the molecular packing in mixed DPPC/C₁₆OH monolayers may be favored by the packing efficiency or geometric accommodation. Furthermore, negative values of excess free energy of mixing were obtained and became significant as the hydrocarbon chain length of alcohols increased, which indicates there were attractive interactions between DPPC and long-chain alcohols. In each free energy of mixing–composition curve, there was only one minimum and thus a phase separation did not exist for mixed DPPC/long-chain alcohol monolayers.