压缩速度对Surfactin在单分子膜内聚集行为的影响

研究了一种微生物脂肽——Surfactin(表面活性素)在气/液界面形成的单分子膜性质, 测定了压缩速度对其单分子膜的表面压-分子面积(π-A)曲线的影响. 结果表明, Surfactin单分子膜铺展在pH＝2酸性亚相上的过程是一个亚稳过程. 通过原子力显微镜(AFM)观察了不同压缩速度时在25 mN•m－1下转移的Langmuir-Blodgett (LB)膜. 在中等压缩速度(0.6 nm2•mol－1• min－1)时转移的LB膜表面观察到分布均匀、排列规则、类似球形的表面聚集体, 而在其它压缩速度下, 形成了按一定规则分布的表面团簇结构. 结合π-A曲线和AFM图像, 提出了Surfactin表面聚集体在气/液界面上的形成机制.

Effect of Compression Speed on Aggregation Behavior of Surfactin in Langmuir Monolayer

The interfacial behavior of surfactin, a microbial lipopeptide, was investigated. The surface pressure-molecular area (π-A) isotherms were recorded as a function of compression speed. It was found that the π-A isotherms on subphase at pH＝2 were compression-speed dependent, indicating that the isotherms are under non-equilibrium in the condition. The LB films of surfactin monolayer under different compression speeds were imaged by atomic force microscopy (AFM). The AFM images showed that surfactin molecules could form homogeneous quasi-circular aggregates under the moderate compression speed (0.6 nm2•mol－1•min－1), while they gathered into surface clusters under other investigated speeds. Based on the results presented here, a mechanism by which molecules in monolayer would self-assemble into surface aggregates was proposed.