Dynamics of molecular recognition

我们已经研究了四个主题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学研究，（3）分子识别调控的电子转移过程，（4）氟卟啉和重构肌红蛋白。1.醌类化合物与四羟基卟啉的诱导-拟合结合导致卟啉的阻转异构化。此外，通过确定结合的热力学参数，证明了在结合靶客体之前柔性核碱基受体的预组织。用圆二色光谱研究了卟啉-氨基酸体系的相互作用模式。两点识别通过发色团之间的静电耦合导致分裂型诱导CD。合成了新型的手性卟啉化合物，这些化合物对氨基酸酯具有中到高的对映选择性。还制备了酒石酸、天冬氨酸和糖的受体。这些受体对客体表现出很高的区域选择性。通过设计猝灭剂的结合位点，实现了光化学驱动下单重态卟啉与醌或紫精的快速电子转移。肌红蛋白中锌卟啉与醌的电子转移是从单重态开始的，其速率比二氯甲烷中慢一个数量级。4.人工血红素对肌红蛋白的重构表明，血红素与脱辅基蛋白的相互作用可分为1，2，3，4-烷基的非极性作用和6，7-丙酸酯的极性作用。丙酸基团和蛋白质之间的极性相互作用被发现稳定氧血红素。

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.