Water Accessibility to the Binding Cleft as a Major Switching Factor from Entropy-Driven to Enthalpy-Driven Binding of an Alkyl Group by Synthetic Receptors
作者:Sayaka Matsumoto、Hiroya Iwamoto、Tadashi Mizutani
DOI:10.1002/asia.200900679
日期:2010.5.3
drove the binding of the alkyl group with the enthalpic driving force being dominant. The binding site of the four‐pillared receptor (1) is open and accessible to water molecules, and is more hydrophilic than that of the eight‐pillared receptor (4). We propose that the alkyl chains of 1 are exposed to water to produce a room to accommodate the guest to result in enthalpy‐driven hydrophobic binding, whereas
确定了烷基吡啶与水溶性锌卟啉受体的结合中的自由能,焓和熵的变化,以及水对结合裂隙的可及性的变化,以解释为什么疏水作用的驱动力在某些情况下是焓,而在另一些情况下是熵。卟啉锌带有四个烷基支柱,其末端增溶的聚(氧化乙烯)(POE)链的分子量为750(1),八个烷基支柱,其末端增溶的POE链的分子量为350(3),并且具有八个烷基支柱,其分子量分别为350(3)分子量750的POE(4)具有结合裂隙,其水可及性以该顺序降低,如通过咪唑/吡啶的结合选择性所揭示的。尽管所有这些卟啉表明,结合(-Δ的自由能G ^ ö)线性增加作为烷基客体的加长(-Δ ģ ö每CH 2为2.6,2.8和2.6千焦耳摩尔-1为1,分别为3和4),自由能获取的来源有很大不同。受体1与最亲水的结合位点由焓驱动力结合的烷基(4- pentylpyridine青睐通过ΔΔ过度-4-甲基吡啶ħ ö = -16.4千焦摩尔-1),而受体4与由熵驱动力最疏水的结合位点(4-