Evidence for Partially Bound States in Cooperative Molecular Recognition Interfaces
Evidence for Partially Bound States in Cooperative Molecular Recognition Interfaces
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DOI：
10.1021/ja803434z
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发表时间：
2008-12-31
影响因子：
15
通讯作者：
Turega, Simon M.
中科院分区：
文献类型：
--
作者：
Chekmeneva, Elena;Hunter, Christopher A.;Turega, Simon M.
具有4个酰胺h键位点的锌卟啉为协同多点结合相互作用的研究提供了一种刚性分子受体。利用紫外/可见吸收、H-1和P-31核磁共振光谱以及等温滴定量热法在五种不同溶剂中研究了该受体与多种含0、1和2个氢键位点的吡啶配体的相互作用。结果是根据一个结合状态来分析的，这个结合状态由不同的络合物组成，其中形成了零、一个或两个潜在的氢键相互作用。决定系统行为的关键参数是氢键相互作用的结合常数K-H和分子内相互作用的有效摩尔浓度EM的乘积。在这里报道的系统中，所有分子内相互作用的EM为0.1-1 M。对于强氢键（非极性溶剂中的大K-H），所有的相互作用都是在配合物中形成的，完全束缚态占主导地位。在这种情况下，额外的结合相互作用会产生复合物稳定性的增量增加。然而，对于较弱的氢键（极性溶剂中的小K-H），由于部分结合态的占位，额外相互作用的形成不会导致配合物整体稳定性的增加。
A zinc porphyrin equipped with four amide H-bonding sites provides a rigid molecular receptor for the study of cooperative multipoint binding interactions. The interaction of this receptor with a variety of pyridine ligands bearing zero, one, and two H-bonding sites has been studied using UV/vis absorption, H-1 and P-31 NMR spectroscopy, and isothermal titration calorimetry in five different solvents. The results are analyzed in terms of a bound state that populates an ensemble of different complexes in which zero, one, or two of the potential H-bond interactions are formed. The key parameter that determines the behavior of the system is the product of the association constant for the H-bond interaction, K-H, and the effective molarity for the intramolecular interaction, EM. In the system reported here, EM is 0.1-1 M for all of the intramolecular interactions. For strong H-bonds (large K-H in nonpolar solvents), all of the interactions are formed in the complex and the fully bound state dominates. In this Case, additional binding interactions produce incremental increases in complex stability. However, for weaker H-bonds (small K-H in polar solvents), the formation of additional interactions does not lead to an increase in the overall stability of the complex, due to the population of partially bound states.