Langmuir膜分子动力学模拟中的头基效应

运用分子动力学方法研究了Ｌａｎｇｍｕｉｒ膜的结构和相变特性，比较了不同的头基模型对模拟的影响。发现在压膜过程中，膜分子的结构和排列存在相变，其中，分子脂肪链的倾角随着膜内每分子所占面积的增大而增大，分子链内无序的主要原因是脂肪链两端二面角的扭曲造成的。由不同模型模拟得出，带电模型的分子分布比较紊乱，倾角较小。这说明亚相环境和头基的不同，会影响模拟得的膜分子的排列，选择合理的头基模型非常重要。     

聚甲基丙烯酸甲酯单分子膜的静、动态弹性

通过测量分析两个不同分子量的聚甲基丙烯酸甲酯(PMMA)单分子膜的π-A等温线及其微分曲线,讨论了PMMA单分子膜成膜过程和分子量对膜相变状态的影响,并用动态膜障振动法测量了PMMA单分子膜的动态弹性.结果表明,分子链的相互作用(如扭曲和缠绕)在膜的形成中起着重要的作用,并影响膜的静、动态性质.单分子膜的静、动态弹性都有两相特性,且前者比后者小.随着分子量的增大,膜的凝聚性和稳定性都增强,静、动态弹性都增大.     

Interaction of Egg-Sphingomyelin with DOPC in Langmuir Monolayers

Lipid rafts are a dynamic microdomain structure found in recent years, enriched in sphin-golipids, cholesterol and particular proteins. The change of structure and function of lipid rafts could result in many diseases. In this work, the monolayer miscibility behavior of mixed systems of Egg-Sphingomyelin (ESM) with 1, 2-dioleoyl-sn-glycero-3-phosphocholine was in-vestigated in terms of mean surface area per molecule and excess molecular area ΔA_ex at certain surface pressure, surface pressure and excess surface pressure Δπ_ex at certain mean molecular area. The stability and compressibility of the mixed monolayers was assessed by the parameters of surface excess Gibbs free energy ΔG_ex, excess Helmholtz energy ΔH_ex and elasticity. Thermodynamic analysis indicates ΔA_ex and Δπe_ex in the binary systems with positive deviations from the ideal behavior, suggesting repulsive interaction. The max-imum of ΔG_ex and ΔH_ex was at the molar fraction of ESM of 0.6, demonstrating the mixed monolayer was more unstable. The repulsive interaction induced phase separation in the monolayer     

气液界面磷脂单分子膜的表面增强拉曼光谱

采用纳米银胶作为成膜亚相, 原位获得了十八胺单分子膜、十八胺/卵磷脂复合膜的表面增强拉曼信号.研究表明,增强主要来源于亚相中的银粒子与成膜分子之间较强的作用.通过在磷脂膜内添加十八胺分子辅助增强而获取了卵磷脂的分子振动信息.     

Langmuir单分子膜的动态稳定性:

应用KSV LB-5000型Langmuir膜天平的VISCOS模式,对硬脂酸和19,21-二炔廿二碳酸(DDA)单分子膜在有无亚相离子、不同目标膜压、不同膜障振动频率和不同温度下的动态稳定性作了研究.实验表明,单分子膜的目标膜压越低,膜障交变振动的频率越低,单分子膜越稳定,亚相中加有金属正离子对单分子膜的动态稳定性也有利.     

乳化工艺对微胶囊型硬脂酸相变材料热性质的影响

以硬脂酸为芯材, 碳酸钙为壁材, 采用原位聚合法制备了微胶囊型相变材料; 通过扫描电子显微镜、 红外光谱及差热-热重分析对其表面形貌和热性质进行了表征; 通过改变乳化剂的种类及用量, 研究了乳化工艺对微胶囊型相变材料表面形貌、 相变温度和包覆率的影响. 实验结果表明, 在选用的3种乳化剂十二烷基苯磺酸钠、 十六烷基三甲基溴化铵和曲拉通X-100中, 十二烷基苯磺酸钠相对效果最好, 乳化剂与芯材最佳质量比为0.5%, 相变温度为112.24 ℃时, 封装率达到92.1%.     

长脂链巴比妥酸和四氨基嘧啶的分子组装体的研究

长脂链巴比妥酸和四氨基嘧啶的分子组装体的研究王志强，王力彦，张希，沈家骢（吉林大学分子光谱与分子结构开放实验室，长春，１３００２３）关键词分子识别，分子组装体，长脂链巴比妥酸，四氨基嘧啶靠氢键、静电、疏水等弱相互作用及其协同作用，在气／液、液／液及液...     

Enantioselective Recognition of Amino Acid by Differential Pulse Voltammetry in Molecularly Imprinted Monolayers Assembled on Au Electrodes

An electrochemical sensor based on L ‐cysteine SAM imprinted by L ‐serine has been developed for the detection of L ‐serine. The sensor shows some entantioselectivity toward L ‐serine and a stable response establishes within 5 min. The peak current intensity of potassium ferricyanide quantified by differential pulse voltammetry (DPV) decreased linearly with increasing L ‐serine concentration from 10 to 100 μM with a gradient of 20.91 nA μM^?1. The detection limit was 4.32 μM. The coefficient of enantiometric selectivity of the molecularly imprinted SAM was about 3.0. Compounds with similar structure as serine caused much less response.     

分子动力学模拟多巴在自组装膜上的黏附性

为了更好地理解贻贝在表面的黏附机理,实现水下胶黏,采用分子动力学方法研究了多巴在自组装膜上的黏附性:采用伞形取样和加权柱状图分析方法计算了多巴在不同自组装膜表面的黏附自由能,使用拉伸分子动力学模拟研究了多巴在不同自组装膜表面上黏附后的脱附力.结果表明,多巴在带负电的羧基自组装膜上的黏附能比在带正电的氨基自组装膜上的大,多巴更容易黏附到带负电表面;多巴在带电表面的黏附能比未带电表面的黏附能更强,表明在带电表面黏附更稳定.进一步分析了多巴在不同表面的取向分布,发现多巴与不同表面相互作用的方式不同:与疏水表面主要通过苯环相互作用;与亲水表面主要通过羟基相互作用;与负电表面主要通过氨基相互作用;与正电表面主要通过羧基相互作用.通过模拟比较了多巴在不同自组装膜上的脱附力,发现多巴在带电表面的脱附力比在未带电表面的大,与黏附能的趋势一致.对比4种非带电表面的脱附力,发现多巴在疏水性甲基自组装膜表面的脱附力最大,黏附更稳定,随着表面疏水性的增加,脱附力增大,黏附稳定性增强.本工作可为研发新型水下胶黏剂提供理论指导.     

硬脂酸法制备SO42-/Fe2O3-SiO2固体酸及其催化性能的初步探讨

首次用硬脂法制备了Fe2O3-SiO2混合氧化物,经浸渍H2SO4后再焙烧得SO4^2-/Fe2O3-SiO2固体酸催化剂。用TEM,XRD,N2吸附/脱附和TG-DTA等手段对其进行了表征,结果显示制得的Fe2O3-SiO2混合氧化物具有多孔结构,且随着Si含量的增大,其比表面积明显增大,但孔径减小。用乙酸/丁醇酯化催化反应评估了该固体酸的催化性能。     

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     

硬脂酸单分子膜上电沉积Ag膜的研究

通过电沉积方法,以气/液界面上形成的硬脂酸单分子膜为模板诱导沉积金属银膜.考察了镀液pH值、单分子膜表面压及沉积电位对银膜形貌及结构的影响.实验发现,酸性镀液的气/液界面上形成的单分子膜不能诱导沉积银,而在中性和碱性镀液的气/液界面上可以诱导银膜的生长.当单分子膜处于液态或固态时,气/液界面有银膜形成;液态单分子膜上的银膜生长速度较快,且银膜的结构一致.随着电极电位的升高,银膜沉积的速度加快,呈环状向外生长的圆形银膜逐渐变得不规则.将不同实验条件下的银膜转移出来,采用扫描电镜(SEM)、透射电镜(TEM)对银膜的结构与形貌进行了表征.研究表明,银首先在单分子膜上异相成核,由八面体构型逐渐发展成星型,最终在气/液界面形成具有松枝状微观结构的光亮银膜.     

分子动力学方法研究纳米摩擦问题

分子动力学方法中忽略了电子相互作用,因而具有高效率,可以从原子水平研究大体系的动态过程。随着计算技术的进步,分子动力学逐渐在纳米工程领域显现了巨大的应用前景。本文综述了利用分子动力学方法从微观角度研究摩擦行为的进展,同时也就其进一步的应用做了展望。     

Catalytic Oxidation of Ascorbic Acid on 2D and 3D Monolayers of 4‐Hydroxythiophenol

Monolayers of 4‐hydroxythiophenol (4‐HTP) immobilized on gold electrode (2D SAMs) or gold nanoclusters (3D SAMs) lead to catalytic oxidation of ascorbic acid (AA). The catalytic role of the modified clusters was revealed by comparing the electrodes covered by 1,9‐nonanedithiol and the same nonanedithiol monolayer decorated by 4‐HTP protected clusters. The 4‐HTP protected gold nanoclusters supported on a metal surface using a monolayer of 1,9‐nonanedithiol as the bridge, transferred charge to ascorbic acid (AA) molecule in the solution more efficiently than when the same 4‐HTP monolayer was formed directly on the gold electrode.     

Molecular Dynamics Simulation on Scale Inhibition Mechanism of Polyepoxysuccinic Acid to Calcium Sulphate

Molecular dynamics simulation has been performed to simulate the interaction between PESA and the (001) face of anhydrite crystal CaSO₄ at different temperatures with the presence of various number of H₂O molecules. The results show that PESA can effectively prevent the growth of CaSO₄ scale at 323-343 K. At the same temperature, the binding energy between PESA and the (001) face of CaSO₄ for systems with various number of H₂O has the order of E_bind(0H₂O)>E_bind(200-400H₂O)>E_bind(100H₂O). For the same system at different temperatures the binding energies are close and are mainly contributed from the Coulomb interaction, including ionic bonds. The bonds are formed between the calcium atoms of anhydrite scale crystal and the oxygen atoms of the carboxyl group of PESA. Hydrogen bonds are formed between the O atoms of the carboxyl group of PESA and the H atoms of H2O. van der Waals interaction is conducive to the stability of the system of PESA, H₂O, and CaSO₄. The radial distribution functions of O(carbonyl of PESA)-H(H₂O),O(CaSO₄)-H(H₂O), and O(CaSO₄)-H(PESA) imply that solvents have effects on the anti-scale performance of PESA to CaSO₄.     

对高分子体系进行分子动力学模拟方法的研究

以单链聚乙烯为例,研究了多种对高分子体系进行分子动力学模拟的方法.结果表明,不同的力场条件可以导致明显不同的结果.在使用OPLS力场的真空条件下.在100K体系出现了玻璃化现象,在200和300K条件下体系出现了局部结晶现象,而在400和500K体系出现了熔化现象.在给定体系中加入周期性边界和在300K下进行分子动力学模拟,无序和结晶状态都具有一定的稳定性.     

Salen Zn对氨基酸甲酯体系的手性分子识别研究

用光谱滴定法测定了手性SalenZn与D-和L-氨基酸甲酸客体在CHCl3中的分子识别反应的缔合常数,其大小顺序为K(LeuOMe)>K(ValOMe)>K(AlaOMe);K(ThrOMe)>K(SerOMe)>K(TyrOMe);且X(D型)>K(L型).根据van'tHoff方程确定了反应体系的热力学函数,并对体系的熵-焓补偿关系和对映体选择性进行了讨论.用分子力学和量子化学方法,对体系 的识别行为进行了计算研究,从理论上对实验现象及识别过程的规律性给予了合理解释.     

金丝桃素分子结构及其与HIV病毒蛋白酶作用的分子动力学研究

采用用计算化学方法研究金丝桃素分子结构特征, 并用分子动力学方法研究其与HIV蛋白酶的相互作用, 探讨其可能的抗HIV病毒作用机理. 结果表明, 金丝桃素分子结构具有刚性特征, 与HIV蛋白酶在酶的催化活性位点与ASP-A25 and ASP-B25以氢键作用相结合.     

卟啉自组装膜与分子信息存储

基于卟啉化合物良好的光电性能,结合自组装膜技术,对其信息存储进行了研究.卟啉分子单体的结构、自组装膜表面卟啉的空间定位以及自组装膜基底材料的选择等对卟啉的信息存储产生着重要影响.目前,卟啉自组装膜的信息存储研究已由单点存储向超高密度多点存储发展.     

Incorporation of Molecular Reorientation into Modeling Surface Pressure-Area Isotherms of Langmuir Monolayers

Langmuir monolayers can be assembled from molecules that change from a low-energy orientation occupying a large cross-sectional area to a high-energy orientation of small cross-sectional area as the lateral pressure grows. Examples include cyclosporin A, amphotericin B, nystatin, certain alpha-helical peptides, cholesterol oxydation products, dumbbell-shaped amphiphiles, organic–inorganic nanoparticles and hybrid molecular films. The transition between the two orientations leads to a shoulder in the surface pressure-area isotherm. We propose a theoretical model that describes the shoulder and can be used to extract the energy cost per molecule for the reorientation. Our two-state model is based on a lattice–sublattice approximation that hosts the two orientations and a corresponding free energy expression which we minimize with respect to the orientational distribution. Inter-molecular interactions other than steric repulsion are ignored. We provide an analysis of the model, including an analytic solution for one specific lateral pressure near a point of inflection in the surface pressure-area isotherm, and an approximate solution for the entire range of the lateral pressures. We also use our model to estimate energy costs associated with orientational transitions from previously reported experimental surface pressure-area isotherms.