Cucurbit[8]uril and Blue-Box: High-Energy Water Release Overwhelms Electrostatic Interactions
Cucurbit[8]uril and Blue-Box: High-Energy Water Release Overwhelms Electrostatic Interactions
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DOI：
10.1021/ja407951x
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发表时间：
2013-10-02
影响因子：
15
通讯作者：
Nau, Werner M.
中科院分区：
文献类型：
--
作者：
Biedermann, Frank;Vendruscolo, Michele;Nau, Werner M.
水溶液中高亲和性和分析物选择性受体的设计是超分子化学中的一个突出问题。针对水的独特性质的重点，我们在这里提出了一个新的战略，实现这一目标，并支持它的分子动力学模拟和量热测量。我们说明的程序中的情况下，自组装的刚性大环葫芦[8]脲（CB 8）和双阳离子辅助客人（AG）的1：1复合物。这些CB 8中心点AG复合物含有残余的水分子，其构象空间和氢键形成能力受到受体的几何限制和疏水空腔的限制。我们表明，在包含的分析物形成1：1：1的CB 8中心点AG中心点分析物复合物，这些高能量的空腔水分子被释放到水的散装，提供了一个强大的吸附驱动力的协会，并导致在结合常数高达10（6）M-1的芳香族分析物。这种结合模型是支持大溶剂和溶剂同位素效应的测量。CB 8中心点AG受体的选择性可以通过辅助客体的合理选择而被修改或甚至切换到小的脂肪族分析物，证明了这种自组装受体的可调识别特征。此外，通过将结果与广泛研究的大环主体环双（百草枯-对亚苯基）（所谓的蓝盒）的结果进行比较，表明在水溶液中，从CB 8中心点AG腔释放高能水分子比使用直接主客体相互作用更有利
The design of high-affinity and analyte-selective receptors operating in aqueous solutions is an outstanding problem in supramolecular chemistry. Directing the focus toward the unique properties of water, we present here a new strategy toward this goal and support it by molecular dynamics simulations and calorimetric measurements. We illustrate the procedure in the case of self-assembled 1:1 complexes of the rigid macrocycle cucurbit[8]uril (CB8) and dicationic auxiliary guests (AG). These CB8 center dot AG complexes contain residual water molecules whose conformational space and hydrogen-bond formation ability is restricted by the geometrically confined and hydrophobic cavity of the receptor. We show that upon inclusion of an analyte to form a 1:1:1 CB8 center dot AG center dot analyte complex, these high-energy cavity water molecules are released to the aqueous bulk, providing a strong enthalpic driving force to the association, and resulting in binding constants of up to 10(6) M-1 for aromatic analytes. This binding model is supported by the measurements of large solvent and solvent isotope effects. The selectivity of the CB8 center dot AG receptor can be modified or even switched toward small aliphatic analytes by a rational choice of the auxiliary guest, demonstrating the tunable recognition features of such self-assembled receptors. Furthermore, by comparison of the results to those for the extensively studied macrocyclic host cyclobis(paraquat-p-phenylene)the so-called blue-boxit is shown that in aqueous solution the release of high-energy water molecules from the CB8 center dot AG cavity can be more favorable than the use of direct hostguest interactions