Monolayer behavior of binary systems of lactonic and acidic forms of sophorolipids: thermodynamic analyses of Langmuir monolayers and AFM study of Langmuir-Blodgett monolayers.
Monolayer behavior of binary systems of lactonic and acidic forms of sophorolipids: thermodynamic analyses of Langmuir monolayers and AFM study of Langmuir-Blodgett monolayers.
复制标题
槐糖脂内酯和酸性二元系统的单层行为：Langmuir 单层的热力学分析和 Langmuir-Blodgett 单层的 AFM 研究。
DOI：
10.5650/jos.ess13047
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发表时间：
2014
影响因子：
1.5
通讯作者：
D. Kitamoto
中科院分区：
文献类型：
--
作者：
T. Imura;D. Kawamura;T. Taira;Tomotake Morita;T. Fukuoka;Kenichi Aburai;H. Sakai;M. Abe;D. Kitamoto
首先通过原子力显微镜 (AFM) 和 Langmuir 单层技术评估 Starmerellaombicola NBRC 10243 产生的内酯型和酸性形式槐糖脂 (SL) 的协同效应和混溶性。纯内酯槐糖脂（LS）单层的π-A等温线主要表现出液体膨胀的单层，而酸性槐糖脂（AS）单层的π-A等温线则表现出液体缩合的单层，这表明SL的内酯化使分子变得更大并阻止它们采用密堆积排列。混合 LS/AS 单层的每个分子的平均面积图与理想曲线存在正偏差，这意味着 LS 和 AS 分子是可混溶的。有趣的是，过量面积 (Aex) 与理想值的正偏差在摩尔分数 (XAS) 为 0.3 时最显着，这与培养物中 S. bidicola 分泌的 LS/AS 混合物的组成非常相似。以 20 mN/m 传输的混合 LS/AS 单层的 AFM 图像显示没有相分离的微域结构，而是显示所有组合物的小突出物体，表明 LS 和 AS 是部分混溶的，正如与理想曲线的正偏差所预测的那样。 AFM 图像的横截面分析表明，观察到的突出物体是在 LS/AS 单层上形成的富含 AS 的单层。我们的结果清楚地表明，AFM 与 Langmuir 技术相结合可用于探索微生物产品的混溶性和协同效应。
The synergic effect and miscibility of the lactonic and acidic forms of sophorolipids (SLs) produced by Starmerella bombicola NBRC 10243 were first evaluated through atomic force microscopy (AFM), together with the Langmuir monolayer technique. The π-A isotherm of a pure lactonic sophorolipid (LS) monolayer mostly exhibited a liquid expanded monolayer, while that of an acidic sophorolipid (AS) monolayer showed a liquid condensed monolayer, suggesting that the lactonization of SLs makes the molecules more bulky and prevents them from adopting a close-packed arrangement. Plots of the mean area per molecule of mixed LS/AS monolayers gave positive deviations from the ideal curves, implying that the LS and AS molecules are miscible. Interestingly, the positive deviation of excess area (Aex) from ideality was most significant at a mole fraction (XAS) of 0.3, which closely resembles the composition of the LS/AS mixture secreted by S. bombicola in culture. The AFM images of mixed LS/AS monolayers transferred at 20 mN/m revealed no phase-separated microdomain structures, but rather showed small protruding objects for all compositions, indicating that LS and AS are partially miscible, as predicted by the positive deviations from the ideal curves. Cross-section analysis of the AFM images indicated that the observed protruding objects are AS-rich monolayers formed on the LS/AS monolayer. Our results clearly demonstrate that AFM combined with the Langmuir technique is useful for the exploration of the miscibility and synergic effects of microbial products.