Department of Applied Chemistry, College of Food & Biology Engineering, Zhejiang Gongshang University, Hangzhou, Zhejiang 310035, PR China.
J Phys Chem B. 2011 Mar 3;115(8):1798-806. doi: 10.1021/jp106385x. Epub 2010 Dec 29.
Molecular recognition by means of multiple hydrogen bonds is of great importance in biological functions. In this paper, an orotic acid derived bolaamphiphile 1,12-diaminododecane diorotate (DDO) with molecular recognition function moieties was designed. Both self-aggregation behavior and molecular recognition with melamine were extensively examined. This bolaamphiphile itself can form vesicles easily in aqueous solutions at 25 °C. Steady-state fluorescence was used to characterize the detailed molecular recognition process. The fluorescence of melamine was quenched more effectively by the spontaneously formed vesicles than by the monomers of the surfactant. Two mechanisms were involved in the fluorescence quench process. At lower concentration, the fluorescence of melamine was found to be quenched by static complex formation. While at higher concentration, both static and dynamic quenching mechanisms coexisted in interaction process. Thermodynamic parameters measured by isothermal titration calorimetry showed that the free energy (ΔG) is negative, indicating that binding of DDO molecules with melamine is favorable energetically. Hydrogen-bonded interactions contribute comparatively a lot for the DDO monomer binding with melamine; at the higher concentration above its critical aggregation concentration, the dissociation of the aggregates take place and lead to an entropically driven molecular recognition process. As complicated binding sites can be constructed through self-assembly at the vesicle interface rather than simple molecular modules, this bolaamphiphile with the molecular recognition functional group may make it possible to generate well-defined recognition sites to mimic biomolecular receptors. Moreover, the present research will give a guide to design chemosensors for melamine detection based on molecular recognition.
分子通过多重氢键识别在生物功能中具有重要意义。本文设计了一种具有分子识别功能基团的乳清酸衍生的两亲分子 1,12-二氨基十二烷二乳酸盐（DDO）。广泛研究了其自组装行为和与三聚氰胺的分子识别。这种两亲分子本身在 25°C 的水溶液中很容易形成囊泡。稳态荧光用于表征详细的分子识别过程。与单体相比，三聚氰胺的荧光被自发形成的囊泡更有效地猝灭。荧光猝灭过程涉及两种机制。在较低浓度下，发现三聚氰胺的荧光通过静态复合物形成被猝灭。而在较高浓度下，在相互作用过程中同时存在静态和动态猝灭机制。等温滴定量热法测量的热力学参数表明，自由能（ΔG）为负值，表明 DDO 分子与三聚氰胺的结合在能量上是有利的。氢键相互作用对 DDO 单体与三聚氰胺的结合有很大贡献；在高于其临界聚集浓度的较高浓度下，发生了聚集物的解离，导致了熵驱动的分子识别过程。由于复杂的结合位点可以通过囊泡界面的自组装而不是简单的分子模块来构建，因此具有分子识别功能基团的这种两亲分子可能使生成能够模拟生物分子受体的明确识别位点成为可能。此外，本研究将为基于分子识别设计用于检测三聚氰胺的化学传感器提供指导。
