Department of Chemistry , Tulane University , New Orleans , Louisiana 70118 , United States.
Department of Chemical and Biomolecular Engineering , Tulane University , New Orleans , Louisiana 70118 , United States.
J Am Chem Soc. 2019 Apr 24;141(16):6740-6747. doi: 10.1021/jacs.9b02287. Epub 2019 Apr 10.
The intrinsic structural complexity of proteins makes it hard to identify the contributions of each noncovalent interaction behind the remarkable rate accelerations of enzymes. Coulombic forces are evidently primary, but despite developments in artificial nanoreactor design, a picture of the extent to which these can contribute has not been forthcoming. Here we report on two supramolecular capsules that possess structurally identical inner-spaces that differ in the electrostatic potential (EP) field that envelops them: one positive and one negative. This architecture means that only changes in the EP field influence the chemical properties of encapsulated species. We quantify these influences via acidity and rates of cyclization measurements for encapsulated guests, and we confirm the primary role of Coulombic forces with a simple mathematical model approximating the capsules as Born spheres within a continuum dielectric. These results reveal the reaction rate accelerations possible under Coulombic control and highlight important design criteria for nanoreactors.
蛋白质的内在结构复杂性使得很难确定每个非共价相互作用对酶的显著速率加速的贡献。库仑力显然是主要的，但尽管在人工纳米反应器设计方面取得了进展，但对于这些力可以做出多大贡献的情况仍不清楚。在这里，我们报告了两种具有相同结构内部空间的超分子胶囊，它们在包围它们的静电势（EP）场方面有所不同：一个带正电，一个带负电。这种结构意味着只有 EP 场的变化才会影响被包裹物种的化学性质。我们通过对被包裹客体的酸度和环化速率测量来量化这些影响，并通过一个简单的数学模型来确认库仑力的主要作用，该模型将胶囊近似为连续介电中的 Born 球体。这些结果揭示了在库仑控制下可能实现的反应速率加速，并突出了纳米反应器的重要设计标准。
