Guest-Induced Excimer Formation of .BETA.-Cyclodextrin Modified with a Branched Arm Possessing Two Naphthyl Moieties.
作者:Iwao SUZUKI、Maki ITO、Tetsuo OSA
DOI:10.1248/cpb.45.1073
日期:——
The β-cyclodextrin derivative (DN-β-CyD) having a branched arm derived from L-ornitine and two molecules of 2-naphthoic acid was synthesized for exploring the conformational change associated with guest binding. When DN-β-CyD was alone in a 10% ethylene glycol aqueous solution, one of the naphthoyl residues in the branched arm was accommodated in the DN-β-CyD cavity. This intramolecular self complex was stabilized by the other naphthoyl moiety located ouside of the cavity on the basis of a hydrophobic capping effect. Upon guest binding, the naphthoyl residue residing in the cavity was expelled from the cavity, forming an excimer with the other naphthoyl residue outside of the cavity. DN-β-CyD was not able to bind the guests strongly, owing to the stability of the intramolecular complexation form. Although DN-β-CyD was proven to be a poor host in guest binding, the guest recognition ability of DN-β-CyD could be estimated by the use of guest-induced fluorescence variations. DN-β-CyD could bind both monoterpenes and cholic acid derivatives to nearly the same extent. However, variations in fluorescence intensity induced by guest binding indicated, as a fluproscent sensing system, that DN-β-CyD was able to detect cholic acid derivatives with higher sensitivity than terpenoids.
为了探索与客体结合相关的构象变化,我们合成了具有由 L-鸟氨酸和两分子 2-萘甲酸衍生的支臂的β-环糊精衍生物(DN-β-CyD)。当 DN-β-CyD 单独存在于 10% 的乙二醇水溶液中时,支臂中的一个萘甲酰残基被容纳在 DN-β-CyD 的空腔中。位于空腔外侧的另一个萘甲酰基在疏水封盖效应的基础上稳定了这种分子内自复合物。与客体结合后,位于空腔内的萘甲酰基残基被排出空腔,与空腔外的另一个萘甲酰基残基形成准分子。由于分子内复合形式的稳定性,DN-β-CyD 无法与客体紧密结合。虽然 DN-β-CyD 被证明在客体结合方面是一个很差的宿主,但 DN-β-CyD 的客体识别能力可以通过客体诱导的荧光变化来估计。DN-β-CyD 与单萜和胆酸衍生物的结合程度几乎相同。然而,客体结合引起的荧光强度变化表明,作为一种荧光传感系统,DN-β-CyD 能够以比萜类化合物更高的灵敏度检测胆酸衍生物。