【作者】 王夫雨；

【导师】 孙润广；

【作者基本信息】 陕西师范大学 ， 生物物理学， 2012， 硕士

【摘要】 随着科学的发展和实验技术的日趋完善,对于生物膜系统的研究已经扩展到生命科学以外的医学、生物物理学和生物化学等很多学科领域,并逐渐成为各个领域热门而且前沿的课题。研究发现很多生命活动都与生物膜系统的结构和功能有着紧密的联系。生物膜的体外模拟技术是研究生物膜系统的理化特性的简单且有效的方法之一。本文以两种生物膜的脂质分子：二棕榈酸磷脂酰胆碱(1,2-dipalmitoyl-sn-glycero-3-phosphorcholine, DPPC)以及二棕榈酸磷脂酰乙醇胺(1,2-dihexadecanoyl-sn-glycero-3-phosphoethanolamine, DPPE)作为人工生物膜的骨架,通过Langmuir单分子层技术研究了熊果酸与这两种脂质分子组成的二元混合系统单分子层在空气-水界面的相行为。记录和分析了混合单分子层的表面压力与平均分子面积关系曲线(π-A曲线),并以此为基础研究了二元混合单分子层的热力学特性,计算得到了单分子层的相关热力学参数(如弹性模量、平均分子面积、过量分子面积、过量吉布斯自由能等),以分子之间的溶合度为基础,在分子水平上分析了熊果酸和两种脂质分子在二元混合系统单分子层上的动力学特性。利用Langmuir-Blodgett(LB)膜技术结合原子力显微镜对混合单分子层的表面形貌进行了研究,研究结果与混合单分子层的热力学和动力学的理论分析的结果相一致。(一)在熊果酸/二棕榈酸磷脂酰胆碱(UA/DPPC)二元混合单分子层中,π-A曲线随着熊果酸的摩尔比的增加呈现规律性的排列。当熊果酸所占的比例较少时,混合单分子层会出现凝聚现象,此时热力学上也更加稳定,两分子间的相互作用力为引力。随着表面压力的增加,熊果酸分子的排布会出现变化,这会影响混合单分子层的各种性质。在较低的表面压力下,少量的熊果酸容易进入到DPPC的区域,分子之间的吸引力使单分子层出现聚集的形貌,此时熊果酸所起作用于胆固醇的作用相似。与胆固醇的作用不同的是,在高的表面压力下,熊果酸分子发生翻转,使混合单分子层中的分子排布的有序性提高,此时分子间的距离较近,有可能出现两个或者多个分子间的聚集而形成聚集体。原子力显微镜对混合单分子层表面形貌的检测研究也证实了这一现象。(二)熊果酸/二棕榈酸磷脂酰乙醇胺(UA/DPPE)二元混合系统在气-水界面上的Langmuir单分子层的π-A曲线也呈规律性的分布,说明分子之间在气-水界面上存在相互作用,而且两种分子具有可混合性。UA/DPPE混合单分子层上分子间的相互作用比UA/DPPC的程度弱。混合单分子层上两种分子的相互作用程度与各分子的摩尔比例和单分子层的表面压力都有关系。在熊果酸的摩尔分数较小时,单分子层会出现有缺陷的膜的形貌,随着熊果酸含量的增加,单分子层上出现更明显的聚集现象。随着表面压力的增加,熊果酸分子脂质分子的分布和排列方式都会出现变化,混合单分子层的表面形貌相应也会出现变化。本文研究分析了熊果酸分别与两种脂质分子形成的二元混合系统单分子层在空气-水界面的相行为。发现熊果酸与这两种脂质分子之间都存在相互作用：在低表面压力时,熊果酸的作用效果与生物膜的重要组成成分-胆固醇相似；在高表面压力时,由于分子间距减小而排布更紧密,熊果酸分子结构的特性使分子间的相互作用发生变化。经过对比分析发现,熊果酸与不同的脂质分子间的作用程度不同。更多还原

【Abstract】 With the development of science and the increasingly improved experimental techniques, the study of biomembrane system has been extended to medicine, biophysics and biochemistry, and other interdisciplinary fields beyond the life sciences, and gradually became popular and frontier topics of each fields. Study found that many life activities are closely linked with the structure and function of biomembrane systems. Biomembrane in vitro simulation technology is one of the simple and effective methods to research the physical and chemical characteristics of biomembrane system.1,2-dipalmitoyl-sn-glycero-3-phosphor-choline (DPPC) and1,2-dihexadecanoyl-sn-glycerol-3-phosphoethanolamine phosphatidyl-ethanolamine (DPPE) were chosen as the skeleton of the artificial membrane. The phase behavior of the binary mixtures system monolayer consisted of ursolic acid and the two lipid molecules at the air-water interface has been studied by π-A isotherm measurement and analysis based on the Langmuir monolayer technique. The thermodynamic properties of binary mixed monolayer (such as elastic modulus, the average and excess area per molecule, excess Gibbs free energy and interaction parameters) was investigated based on molecular fusion level. The theoretical analysis of the thermodynamics and kinetics of the mixed monolayer was indicated by the study of surface morphology of the artificial membrane using the Langmuir-Blodgett (LB) film technology combined with atomic force microscopy(I) In the binary mixtures of ursolic acid/1,2-dipalmitoyl-sn-glycerol-3-phosphor-choline (UA/DPPC) monolayer. With the gradually increased molar faction of ursolic acid, the arrangement of the π-A isotherms of shown regularity. When the faction of ursolic acid is small, the agglutination occurs in the mixed monolayer and the thermodynamically of mixed monolayer is more stable. The interaction between the two molecules is attraction. With the increase of surface pressure, the arrangement of ursolic acid molecules changed, which would affect the properties of the mixed monolayer. At lower surface pressure, a small amount of ursolic acid can easily access into the DPPC area, the attraction between the molecular on monolayer makes the appearance of aggregation morphology. At this time, ursolic acid plays the same role as cholesterol. Differed from the cholesterol, at high surface pressure, ursolic acid molecules overturned, which could increase the arrange order of the molecules in the mixed monolayer, and the shortage of the distance between molecules. The aggregation between two molecules may induce the formation of dimers. The detection of the mixed monolayer surface morphology using atomic force microscopy indicated this phenomenon.(II) Langmuir monolayer π-A isotherms of ursolic acid/1,2-dihexadecanoyl-sn-glycero-3-phosphoethanolamine phosphatidyl-ethanolamine (UA/DPPE) binary mixtures at the air-water interface showed a regular distribution. There has interaction between molecules in the air-water interface and the two molecules can be mixed. The interaction of molecular on the UA/DPPE monolayer is weak than on the UA/DPPC. The interaction of different molecules on the mixed monolayer has relationship with the molar fraction and the surface pressure. When the mole fraction of ursolic acid is small, the morphology of monolayer appears defective film. With the increase of the fraction of ursolic acid on the monolayer, obviously aggregation can be found. As the increase of surface pressure, the distribution and arrangement of the lipid molecules and ursolic acid molecules will change. Correspondingly, the surface morphology of monolayer also changes.This article investigated the phase behavior of binary mixed monolayer consisted of ursolic acid and two different lipid molecules in the air-water interface. Interactions exist between ursolic acid and two different lipid molecules. At low surface pressure, ursolic acid played the same role as cholesterol-an important components of the biomembrane. At high surface pressure, as the molecular arrangement more closely, the molecular spacing decreases, the interaction force changed because the characteristic structure of ursolic acid. Comparative analysis found that, the interaction of ursolic acid with two kinds of lipid molecules is different.更多还原