Nanoscale Interfacial Activity of the Natural Lipopeptide, [Asp1, Glu5] Surfactin-C16, and DMPC in Mixed Monolayer

作     者：Yang Ying Zou Aihua song Changsheng Mu Bozhong 

作者机构：Laboratory for Advanced Material and Institute of Applied Chemistry East China University of Science and Technology Shanghai 200237 China Taicang Entry-Exit Inspection and Quarantine Bureau Jiangsu 215400 China 

出 版 物：《Chinese Journal of Chemistry》 (中国化学（英文版）)

年 卷 期：2012年第30卷第12期

页      面：2869-2873页

核心收录：

学科分类：081704[工学-应用化学] 07[理学] 08[工学] 0817[工学-化学工程与技术] 070305[理学-高分子化学与物理] 080501[工学-材料物理与化学] 0805[工学-材料科学与工程（可授工学、理学学位）] 0703[理学-化学] 0822[工学-轻工技术与工程] 082202[工学-制糖工程] 

基　　金：support of this work by Research Fund for the New Teacher of the Doctoral Program of Higher Education of China (No. 200802511024). This work is supported by the National Natural Science Foundation of China (No. 50574040)  the grant from Shanghai Science and Technology Commission (No. 071607014) 

主　　题：surfactin DMPC Langmuir film atomic force microscopy 

摘      要：The dimyristoylphosphatidylcholine （DMPC） and a newly isolated surfactin analogue, [Asp1, Glus] surfactin-C16 in mixed monolayer was studied. Surface pressure-molecular area isotherms combined with atomic force microscopy （AFM） were used to probe the interfacial behavior of DMPC and surfactin-C16. The results show that the miscibility between DMPC and surfactin-C 16 is dependent on surfactin molar fraction （Xs） and surface pressure The two components are partially miscible on pure water （pH= 6） when Xs is 0.5, indicating that there exists mutual interactions between two components. AFM images showed similar pattern in surfactin-C16 monolayer and DMPC/surfactin-C 16 （Xs = 0.5） mixed monolayer. Based on the finding it is believed that DMPC would coalescent into surfactin-C 16 surface clusters in the mixed monolayer. Furthermore, the excess free energy of mixing （△ G^（ex）m ） was calculated to investigate the effect of subphase pH on the miscibility of two components in the mixed monolayer. It is found that the △ G^（ex）m was negative on alkaline subphase （pH= 10） when Xs equals to 0.75, indicating the molecular interactions between surfactin and DMPC are attractive at the condition. The results presented here suggest that hydrophobic interactions between surfactin-C 16 and DMPC play an important role in mutual interactions, and the interfacial activity was influenced by the ionization state of polar groups of surfactin-C 16.