Dynamics of molecular recognition

我们研究了四个方面来阐明分子识别的动力学：(1)分子识别引起的构象变化，(2)多点分子识别的热力学和光谱研究，(3)分子识别调控的电子转移过程，(4)氟卟啉和重组肌红蛋白。1.四羟基卟啉与苯二酚的合适结合导致了卟啉中的阿托异构化。此外，通过测定结合的热力学参数，还证明了在与目标客体结合之前柔性核碱基受体的预组织。用圆二色谱研究了卟啉-氨基酸体系的相互作用模式。两点识别导致分离型诱导CD，通过生色团之间的静电耦合。合成了新型手性卟啉化合物，它们对氨基酸酯表现出中等到高度的对映选择性结合。还制备了酒石酸、天冬氨酸和糖的受体。这些受体对客人表现出很高的区域选择性。通过设计猝灭剂的结合位，实现了卟啉单线态光化学驱动下的电子快速转移。肌红蛋白中锌卟啉与二氯甲烷之间的电子转移是以单重态进行的，电子转移的速度比在二氯甲烷中慢一个数量级。4.人工血红素对肌红蛋白的重组表明，血红素与载脂蛋白之间的相互作用可分为1，2，3，4-烷基的非极性相互作用和6，7-丙酸基的极性相互作用。丙酸基团与蛋白质之间的极性相互作用可以稳定氧合血红素。

We have studied four topics to elucidate the dynamics of molecular recognition : (1) Conformational changes induced by molecular recognition, (2) Thermodynamic and spectroscopic studies of multi-point molecular recognition, (3) Electron transfer process regulated by molecular recognition, and (4) Fluoroporphyrins and reconstituted myoglobin.1.Induced-fit binding of quinones to tetrahydroxyporphyrin results in the atropisomerization in the porphyrin. Also preorganization of flexible nucleobase receptor before binding a target guest was demonstrated by determining thermodynamic parameters of the binding. Porphyrin dimer formation following atropisomerization was also studied kinetically.2.Circular dichroism was used to investigate the interaction mode of porphyrin-amino acid system. Two-point recognition lead to split-type induced CD,through electrostatic coupling between the chromophores. Novel chiral porphyrins were prepared, which show moderate to high enantioselective binding of amino acid esters. Receptors for tartaric acid, aspartic acid and sugars were also prepared. These receptors showed high regioselectivity for the guest. Enthalpy and entropy changes upon complexation were used to estimate conformational changes during complex formation.3.Fast electron transfer from singlet state of porphyrin to quinone or viologens driven photochemically was realized by designing a binding site for quenchers. Electron transfer from zinc porphyrin in myoglobin to quinone which is attached by a peptide spacer occurred from a singlet state with a rate one order of magnitude slower than in dichloromethane.4.Reconstitution of myoglobin by artificial hemes showed that interactions between heme and apoprotein can be split into contributions from non-polar interactions of 1,2,3,4-alkyl groups and polar interactions of 6,7-propionate groups. The polar interactions between propionate groups and protein was found to stabilize oxyheme.