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摘要
The dimyristoylphosphatidylcholine (DMPC) and a newly isolated surfactin analogue, [Asp1, Glu5] 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-C16 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-C16 (XS=0.5) mixed monolayer. Based on the finding it is believed that DMPC would coalescent into surfactin-C16 surface clusters in the mixed monolayer. Furthermore, the excess free energy of mixing (?Gmex) was calculated to investigate the effect of subphase pH on the miscibility of two components in the mixed monolayer. It is found that the ?Gmex 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-C16 and DMPC play an important role in mutual interactions, and the interfacial activity was influenced by the ionization state of polar groups of surfactin-C16.
- 出版日期2012-12
- 单位华东理工大学; 中国科学院长春应用化学研究所
