中文摘要：

乌苏酸（UA）为五环三萜羧基酸类化合物,是一种中药有效成分.它进入细胞的过程与膜脂分子有密切关系.选用生物膜系统中的膜脂分子二棕榈酰基磷脂酰胆碱（DPPC）为代表,通过LB（Langmuir-Blodgett）膜技术获得乌苏酸与DPPC混合单层膜的表面压力/平均分子面积（π-A）曲线.分析了混合单层膜的平均和过量分子面积、弹性系数等热力学参量,并用原子力显微镜进行了研究.比较了乌苏酸/DPPC与胆固醇/DPPC混合单层膜的异同.实验结果表明：乌苏酸能促使DPPC的凝聚;乌苏酸/DPPC两组分的物质的量比与混合单层膜的膜压对单层膜的压缩性、稳定性和热力学特性有影响,对单层膜中不同组分间的混合性以及分子间的相互作用具有重要的影响.

英文摘要：

In this work, the interaction of urasolic acid （UA, a natural pentacyclic triterpene） and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine （DPPC, an important phospholipid in cell membrane） was investi- gated. The mean and excess surface area per molecule, elastic modulus, excess Gibbs energy, and interaction parameter of mixed monolayer were studied based on the surface pressure-area isotherms. The authors found that, as well as cholesterol, UA can induce the DPPC molecules on the monolayer condensation. The stability, compressibility and thermodynamic characteristics of binary system of UA and DPPC are connected with the surface pressure and the mole faction of UA. The AFM experiment supported the conclusion effectively.