酰基氨基酸表面活性剂体系：有序结构表面化学组成与离子特异性效应

Ion specific effects, also known as Hofmeister effects, occur in many biological phenomena including protein folding and enzyme activities. Before any global systemization in biology is possible, the problem of specific ion effects in chemistry has to be understood and brought to order. Because of the complexity of protein system, this project proposes to use acyl amino acid surfactants as model systems, and study the specific ion effects on the morphologies of surfactant aggregates, which may provide molecular rationalization of ion specific effect in protein systems. Interfacial compositions of aggregates, to some extent, control aggregates’ morphologies. However, compared to liquid/liquid, air/liquid, and solid/liquid interfaces, interfacial regions of aggregates are like “black boxes”, and can seldom be studied by experimental method. We plan to use the chemical trapping method, which provides unique quantitative estimates of interfacial concentrations, to characterize the ion specific effects in salt induced aggregation transitions in acyl amino acid surfactant aqueous solutions. The changes of interfacial molarities of water, terminal carboxylate groups and amide carbonyl in the headgroups, and co-ions will be estimated during these transitions. The relationships between aggregate morphology, counterion type, and interfacial molarities of water, molecules (terminal carboxylate groups, and added anions) will be identified. Ultimately, statistical models based on interfacial molarity data, regarded as “fingerprints” of these aggregates, will be built for the prediction of ion specific effect on surfactant aggregate by using machine learning algorithms.

包括蛋白质折叠和生物酶活性在内的众多生命现象都受到离子特异性效应的影响，在化学领域实现对该效应的预测是揭开生命体系中相关现象的前提。鉴于蛋白质体系的复杂性，本项目拟以酰基氨基酸表面活性剂为分子模型，研究特异性离子对其有序结构形态的影响，为在分子水平解析蛋白质体系中的离子特异性效应提供理论依据。有序结构表面（有序结构与单体水溶液间的一层区域）的化学组成在一定程度上决定了有序结构的形态。然而，相较于宏观上的液/液、气/液界面，有序结构表面如同一个“黑箱”，一般实验手段无法聚焦于此。本项目拟利用化学捕集法研究特异性离子对酰基氨基酸表面活性剂有序结构表面水、氨基酸头基中的末端羧基和酰胺键以及共离子浓度的影响，理清有序结构转变中的表观离子特异性效应与微观上其有序结构表面化学组成的相关规律，并利用机器学习算法建模，分析这些存在于有序结构表面的“指纹”数据，形成能够预测有序结构中离子特异性效应的方法。

包括蛋白质折叠和生物酶活性在内的众多生命现象都受到离子特异性效应的影响，在化学领域实现对该效应的预测是揭开生命体系中相关现象的前提。鉴于蛋白质体系的复杂性，本项目以酰基氨基酸表面活性剂为分子模型，深入研究了特异性离子对其自组装、表面活性、泡沫和界面流变等性质的影响。更为重要的是，为在分子水平上阐释该体系有序结构转变过程，利用化学捕集法和分子动力学模拟的手段着重研究了体系有序结构表面化学组成变化中的离子特异性效应。研究明确了特异性盐离子引发的酰基氨基酸表面活性剂有序结构转变过程中伴随着有序结构表面水和酰胺键浓度的急剧变化；归纳出有序结构转变过程中的离子特异性效应与其表面化学组成的变化趋势的一般性规律。另外，研究发现有机铵盐的加入可破坏酰基氨基酸型表面活性剂分子间的氢键作用，并引发具有羧酸和磺酸型头基的酰基氨基酸型表面活性剂体系中的囊泡-胶束转变。本项目将有序结构的表观离子特异性效应与微观上其表面各化学组成的离子特异性效应联系起来，可为实现对酰基氨基酸型表面活性剂有序结构形态的精确调控和在分子水平解析蛋白质体系中的离子特异性效应提供理论依据，同时也为化学捕集法的进一步开发和广泛应用提供了理论支持。本项目的研究成果发表学术论文11篇，申请发明专利3件。