Fluorescence Sensing and Selective Binding of a Novel 4,4′‐Sulfonyldianiline‐Bridged Bis(β‐cyclodextrin) for Bile Salts

Abstract

A novel 4,4'-sulfonyldianiline-bridged bis(b-cyclodextrin (CD)) 2 was synthesized, and its complex stability constants (K s ) for the 1 : 1 inclusion complexation with bile salts, i.e., cholate (CA), deoxycholate (DCA), glycocholate (GCA), and taurocholate (TCA) have been determined in phosphate buffer (pH 7.2) at 258 by fluorescence spectroscopy. The result indicated that 2 can act as efficient fluorescent sensor and display remarkable fluorescence enhancement upon addition of optically inert bile salts. Structures of the inclusion complexes between bile salts and 2 were elucidated by 2D-NMR experiments, indicating that the anionic tail group and the D ring of bile salts penetrate into one CD cavity of 2 from the wide opening deeply, while the phenyl moiety of the CD linker is partially self-included in the other CD cavity to form a host -linker -guest binding mode. As compared with native b-CD 1 upon complexation with bile salts, bis(b-CD) 2 enhances the binding ability and molecular selectivity. Typically, 2 gives the highest K s value of 26200 m À1 for the complexation with CA, which may be ascribed to the simultaneous contributions of hydrophobic, H-bond, and electrostatic interactions. These phenomena are discussed from the viewpoints of multiple recognition and induce-fit interactions between host and guest.

Cooperative molecular recognition of dyes by two bis(β-cyclodextrin)s with aromatic, sulfur-containing, diamine tethers

“…The phosphate buffer (0.10 mol dm -3 , pH 7.20) used in the spectral measurements was prepared from NaH 2 PO 4 and Na 2 HPO 4 . 4,4 0 -Diaminodiphenyl sulfone bridged bis(6-amino-6-deoxy-b-CD) 2 [25] and 4, 4 0 -diaminodiphenyl disulfide bridged bis(6-amino-6-deoxy-b-CD) 3 [26] were prepared according to our previous report. 1 H NMR spectra were recorded on a Bruker AV.…”

Thermodynamics of Resulting Complexes Between Cyclodextrins and Bile Salts

“…The phenyl moiety is not driven out of the CD cavity even after the guest inclusion. To obtain the information about the binding modes between bile salts and sulfonyldianilinebridged -CD 49, 2D ROESY spectra for typical host-guest pairs have further been determined by Zhao et al [32]. The correlation signals, along with the 1:1 binding stoichiometry, jointly indicate a host-linker-guest binding mode between 49 and CA.…”

“…The stoichiometry for the inclusion complexation of sulfonyldianiline-bridged -CD 49 with bile salts has also been determined by the "continuous variation" method and the results indicate that all the bile salts can form 1:1 complexes with 49 [32]. Thermodynamically, the binding constants of 49 with bile salts are larger than those of native -CD 1.…”