单链-Gemini结构变化对多肽表面活性剂自组装行为的影响.docVIP

 单链-Gemini 结构变化对多肽表面活性剂自 组装行为的影响# 曹美文，曹长海* 5 10 15 20 25 30 35 40 （中国石油大学（华东）生物工程与技术中心，山东 青岛 266555） 摘要：通过 Cys 残基在阴离子型多肽表面活性剂分子 V3C 中引入巯基，然后巯基之间氧化连 接形成二硫键，成功制备了完全氨基酸构成的 Gemini 型多肽表面活性剂 V3C-CV3。进一步运 用电导测定、红外光谱、原子力显微镜、pH 滴定等多种技术手段研究了分子结构改变前后 分子基本性质和自组装行为的变化。V3C 单体分子含有巯基和羧基两个 pH 敏感可带电基团， 其临界聚集浓度为 0.16 mM，在云母片上组装为膜状结构，二级结构中β折叠含量达 61.2%。 分子转变为 Gemini 结构 V3C-CV3 之后，临界聚集浓度极大降低，约为 0.02 mM，自组装体则 变得更为规整，为细小的纤维状结构，同时，组装体中β折叠含量也大大提高，约为 76.9%。 因为结构变化前后分子 pKa 值变化很小，推测各基团空间构象的变化而不是分子带电情况的 变化是引起分子基本性质和自组装行为明显改变的根本原因。 关键词：多肽表面活性剂；自组装；单体；Gemini 中图分类号：O648 Effect of Monomer-to-Gemini Structural Change on the Self-Assembly of Peptide Surfactant CAO Meiwen, CAO Changhai (Center for Bioengeering and Biotechnology, China University of Petroleum (East China), ShanDong QingDao 266555) Abstract: The anionic peptide surfactant V3C that bearing hydrosulfide group was produced by introducing Cys residue into the molecule. Then by oxidation of hydrosulfide groups to form disulfide bond, a Gemini peptide surfactant V3C-CV3 was successfully synthesized. The self-assembly behaviors before and after structural change were investigated by techniques of electric conductivity measurement, fourirer transformed infrared spectroscopy, atomic force microscopy, and pH titration. V3C monomers contains pH-sensitive hydrosulfide and carboxyl groups, which can be charged via protonation/deprotonation. It shows critical aggregation concentration (CAC) of 0.16 mM and self-assembles to form membrane on the mica surface. The secondary structures contain 61.2 percent of beta-sheet. When the molecule transformed to Gemini structure of V3C-CV3, the CAC decreases greatly to be only 0.02 mM. The molecular self-assembly turns to be more orderd to form tiny fibers. Simutaneously beta-sheet content in the secondary structure increases to be about 76.9 percent. Since the pKa shows almost no variation before and after the molecular structural change, it is believed that the different self-assembly behaviors are resulte