State Key Laboratory of Bioreactor Engineering and Institute of Applied Chemistry, East China University of Science and Technology, Shanghai 200237, PR China.
J Phys Chem B. 2010 Mar 4;114(8):2712-8. doi: 10.1021/jp908675s.
Surface tension, small angle neutron scattering (SANS), freeze-fracture transmission electron microscopy (FF-TEM), and circular dichroism (CD) have been used to study the self-aggregation properties of the natural lipopeptide [Glu(1), Asp(5)] surfactin-C15 in 0.01 M phosphate buffer solution (PBS) at pH 7.4. It has been found that the critical micelle concentration (cmc) of surfactin is 1.54 x 10(-5) M, the surface tension at the cmc (sigma(cmc)) is 27.7 mN/m, and the area per molecule at the air-water interface is 107.8 A(2). Surfactin molecules adopt a beta-sheet conformation already at low concentrations. This feature probably makes it surface-active at such low concentrations. From SANS and FF-TEM results, it is seen that surfactin exhibits a strong self-assembly ability to form sphere-like micelles and some larger aggregates even at the rare low concentration. The aggregation number of sphere-like micelles is much smaller than that for conventional surfactants of similar alkyl chain length.
表面张力、小角中子散射（SANS）、冷冻断裂透射电子显微镜（FF-TEM）和圆二色性（CD）已被用于研究天然脂肽[Glu(1), Asp(5)]表面活性剂-C15 在 0.01 M 磷酸盐缓冲溶液（PBS）中的自聚集特性在 pH 7.4。已经发现表面活性剂的临界胶束浓度（cmc）为 1.54 x 10(-5) M，cmc 处的表面张力（sigma(cmc)）为 27.7 mN/m，空气-水界面上的每个分子的面积为 107.8 A(2)。表面活性剂分子在低浓度下就采用β-折叠构象。这一特征可能使其在如此低的浓度下具有表面活性。从 SANS 和 FF-TEM 的结果可以看出，即使在罕见的低浓度下，表面活性剂也表现出很强的自组装能力，能够形成球状胶束和一些较大的聚集体。球状胶束的聚集数远小于具有相似烷基链长的常规表面活性剂。
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