Liu Yu, Zhao Yan-Li, Chen Yong, Ding Fei, Chen Guo-Song
Department of Chemistry, State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin 300071, P. R. China.
Bioconjug Chem. 2004 Nov-Dec;15(6):1236-45. doi: 10.1021/bc049870m.
beta-Cyclodextrin dimers bearing an oxamido bis(2-benzoic) carboxyl linker (1) or its metal complexes (2 and 3) were newly synthesized, and their inclusion complexation behavior with a series of representative aliphatic oligopeptides, i.e., Leu-Gly, Gly-Leu, Gly-Pro, Glu-Glu, Gly-Gly, Gly-Gly-Gly, and Glu(Cys-Gly), was elucidated by means of UV/vis, circular dichroism, fluorescence, and 2D NMR spectroscopy in Tris-HCl buffer solution (pH 7.4) at 25 degrees C. The results obtained indicated that metallobridged bis(beta-cyclodextrin)s 2 or 3 could significantly enhance the original molecular binding abilities of parent bis(beta-cyclodextrin) 1 toward model substrates through the cooperative binding of two cyclodextrin moieties and the additional chelation effect supplied by the coordinated metal centers. It is interesting that hosts 2 and 3 displayed an entirely different fluorescence behavior upon complexation with guest oligopeptides. Among the guest peptides examined, 3 showed the highest complex formation constant of 68 200 M(-)(1) for Glu-Glu, up to 510-fold as compared with 1 (135 M(-)(1)), while 1 gave excellent molecular selectivity for Glu(Cys-Gly)/Glu-Glu pair, up to 51-fold. The molecular binding ability and selectivity were discussed from the viewpoints of the induced-fit and multiple recognition mechanism between host and guest.
新合成了带有草酰胺基双（2 - 苯甲酸）羧基连接基的β-环糊精二聚体（1）及其金属配合物（2和3），并通过紫外/可见光谱、圆二色光谱、荧光光谱和二维核磁共振光谱，在25℃、pH 7.4的Tris - HCl缓冲溶液中，阐明了它们与一系列代表性脂肪族寡肽（即Leu - Gly、Gly - Leu、Gly - Pro、Glu - Glu、Gly - Gly、Gly - Gly - Gly和Glu（Cys - Gly））的包合络合行为。所得结果表明，金属桥连双（β-环糊精）2或3可通过两个环糊精部分的协同结合以及配位金属中心提供的额外螯合效应，显著增强母体双（β-环糊精）1对模型底物的原始分子结合能力。有趣的是，主体2和3与客体寡肽络合时表现出完全不同的荧光行为。在所研究的客体肽中，3对Glu - Glu显示出最高的络合形成常数68200 M⁻¹，与1（135 M⁻¹）相比高达510倍，而1对Glu（Cys - Gly）/Glu - Glu对具有出色的分子选择性，高达51倍。从主体与客体之间的诱导契合和多重识别机制的角度讨论了分子结合能力和选择性。
