Department of Chemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio 43210, USA.
J Am Chem Soc. 2010 Jan 20;132(2):773-6. doi: 10.1021/ja908436c.
Some highly efficient enzymes, e.g., acetylcholinesterase, use gating as a tool for controlling the rate by which substrates access their active site to direct product formation. Mastering gated molecular encapsulation could therefore be important for manipulating reactivity in artificial environments, albeit quantitative relationships that describe these processes are unknown. In this work, we examined the interdependence between the thermodynamics (DeltaG(o)) and the kinetics (DeltaG(in)(double dagger) and DeltaG(out)(double dagger)) of encapsulation as mediated by gated molecular basket 1. For a series of isosteric guests (2-6, 106-107 A(3)) entering/exiting 1, we found a linear correlation between the host-guest affinities (DeltaG(o)) and the free energies of the activation (DeltaG(in)(double dagger) and DeltaG(out)(double dagger)), which was fit to the following equation: DeltaG(double dagger) = rhoDeltaG(o) + delta. Markedly, the kinetics for the entrapment of smaller guest 7 (93 A(3)) and bigger guest 8 (121 A(3)) did not follow the free energy trends observed for 2-6. Thus, it appears that the kinetics of the gated encapsulation mediated by 1 is a function of the encapsulation's favorability (DeltaG(o)) and the guest's profile. When the size/shape of guests is kept constant, a linear dependence between the encapsulation potential (DeltaG(o)) and the rate of guests' entering/departing basket (DeltaG(in/out)(double dagger)) holds. However, when the potential (DeltaG(o)) is fixed, the basket discriminates guests on the basis of their size/shape via dynamic modulation of the binding site's access.
一些高效的酶，例如乙酰胆碱酯酶，使用门控作为控制底物进入其活性位点的速率的工具，以指导产物形成。因此，掌握门控分子封装对于在人工环境中操纵反应性可能非常重要，尽管描述这些过程的定量关系尚不清楚。在这项工作中，我们研究了由门控分子篮 1 介导的封装的热力学（ΔG(o))和动力学（ΔG(in)(双剑号）和 ΔG(out)(双剑号）之间的相互依赖关系。对于一系列进入/离开 1 的等构客体（2-6、106-107 A(3))，我们发现主客体亲和力（ΔG(o))与激活的自由能（ΔG(in)(双剑号）和 ΔG(out)(双剑号）之间存在线性关系，该关系符合以下方程：ΔG(double dagger) = rhoDeltaG(o) + delta。值得注意的是，较小客体 7（93 A(3))和较大客体 8（121 A(3))的捕获动力学不符合观察到的 2-6 的自由能趋势。因此，似乎由 1 介导的门控封装的动力学是封装的有利性（ΔG(o))和客体的特性的函数。当客体的大小/形状保持不变时，封装势（ΔG(o))和客体进入/离开篮（ΔG(in/out)(双剑号）的速率之间存在线性关系。然而，当势（ΔG(o))固定时，篮通过动态调节结合位点的进入来基于客体的大小/形状对客体进行区分。
