Sequence-specific multivalent molecular recognition has been recognized to play a major role in biological processes. Furthermore, sequence-specific recognition motifs have been used in various artificial systems in the last years, e.g., to emulate biological processes or to build up new materials with highly specific recognition domains. In this article, we present the preparation of cyclodextrin (CD)-based strands and complementary and non-complementary strands modified with guest molecules and the investigation of their complexation behavior towards each other by isothermal titration calorimetry (ITC). As complementary binding motifs n-butyl and α-CD and adamantane and β-CD were selected. It was found that it is possible to realize sequence-specific molecular recognition by the use of host–guest chemistry, but the recognition motifs as well as the linkages have to be chosen very carefully. In the case of trivalent systems one adamantane moiety must be included to induce preferred formation of 1:1 adducts. Due to the too weak interaction between n-butyl and α-CD these systems have a negative chelate cooperativity and open adducts are preferentially formed. As soon as two adamantane moieties are present, the complementary systems have a positive chelate cooperativity and double-stranded structures are favored over open adducts. In this system the n-butyl moiety provides insufficient discrimination towards α- and β-CD and no sequence specificity is observed. By the combination of three adamantane moieties sequence specificity can be generated. Exclusively with the complementary CD sequence double-stranded structures are formed, with non-complementary strands aggregates of higher stoichiometry are generated.
特异性序列多价分子识别在生物过程中发挥重要作用。此外,近年来,序列特异性识别基序已被用于各种人工系统中,例如,模拟生物过程或构建具有高度特异性识别结构域的新材料。在本文中,我们介绍了基于环糊精(CD)的链和修饰有客体分子的互补和非互补链的制备,并通过等温滴定量热法(ITC)研究它们之间的络合行为。作为互补结合基序,选择了n-丁基和α-CD以及脱氢脂肪烷和β-CD。发现通过使用宿主-客体化学可以实现特异性序列分子识别,但识别基序以及连接必须非常谨慎选择。在三价系统中,必须包含一个脱氢脂肪烷基团以诱导首选形成1:1加合物。由于n-丁基和α-CD之间的相互作用过弱,这些系统具有负螯合协同性,优先形成开放的加合物。一旦存在两个脱氢脂肪烷基团,互补系统具有正螯合协同性,双链结构优于开放的加合物。在这个系统中,n-丁基基团对α-CD和β-CD提供的区分不足,没有观察到序列特异性。通过三个脱氢脂肪烷基团的组合,可以产生序列特异性。仅与互补CD序列一起形成双链结构,而与非互补链形成高摩尔配位聚集体。