Efficient fluorescent sensors of oligopeptides by dithiobis(2-benzoylamide)-bridged bis(beta-cyclodextrin)s: structure in solution, binding behavior, and thermodynamic origin.
Two 6,6'-bis(beta-cyclodextrin)s linked by 2,2'-dithiobis[2-(benzoylamino)ethyleneamino] and 2,2'-dithiobis[2-(benzoylamino)diethylenetriamino] bridges (1 and 2) have been synthesized as cooperative multipoint recognition receptor models for non-aromatic oligopeptides. Their structures in solution and inclusion complexation mechanism are comprehensively investigated by means of circular dichroism, 2D NMR spectra and temperature-dependent fluorescence titrations. The results show that the cooperative 'host-linker-guest' binding mode and the extensive desolvation effect jointly contribute to the guest-induced fluorescence enhancement of bis(beta-cyclodextrin)s. Further examinations on the binding behavior of hosts 1-2 with a series of di- and tri-peptides demonstrate that bis(beta-cyclodextrin) 1 can recognize not only the size/shape of oligopeptides but also the dipeptide sequence, giving an exciting residue selectivity up to 37.5 for Gly-Gly-Gly/Glu-Glu pair and a high sequence selectivity up to 5.0 for Gly-Leu/Leu-Gly pair. These fairly good selectivities are discussed from the viewpoint of cooperative binding, multiple recognition and induced-fit interactions between host and guest.
Liu
Yu
Y
Department of Chemistry, State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin 300071, PR China. yuliu@public.tpt.tj.cn
Yang
Ying-Wei
YW
Chen
Yong
Y
Ding
Fei
F
D005456:Fluorescent Dyes / Q000737:chemistry*; D009842:Oligopeptides / Q000737:chemistry*; D011487:Protein Conformation; D013057:Spectrum Analysis; D013816:Thermodynamics; D047392:beta-Cyclodextrins / Q000737:chemistry*
D005456:Fluorescent Dyes; D009842:Oligopeptides; D047392:beta-Cyclodextrins; C031215:betadex