Small polyanion recognition of a triazolium cyclodextrin click cluster in water

In order to detect small polyanions (sPAs), which play important roles in many biological systems, a triazolium cyclodextrin click cluster (5, hexakis{6-(3-methyl-4-hydroxymethyl-1H-1,2,3-triazolium-1-yl)-6-deoxy}-α-cyclodextrin iodide) was synthesized and characterized. The competition binding to 5 occupied by 5-carboxyfluorescein of inositol-1,4,5-trisphosphate (IP₃), phytic acid, adenosine triphosphate (ATP), ethylenediaminetetraacetic acid (EDTA), glucose, and glucose-6-phosphate was evaluated by UV/vis titration in HEPES (10 mM, pH 7.4) : methanol (1 : 1, v/v). We obtained the binding constants of IP₃ and phytic acid to 5 (1.4 × 10⁶ and 1.9 × 10⁶ M⁻¹, respectively); however, the binding constants of ATP and EDTA were significantly lower (2.1 × 10⁵ and 4.5 × 10⁴ M⁻¹, respectively). Moreover, glucose and glucose-6-phosphate did not show any detectable binding. In addition, the sPA recognition of the triazolium cyclodextrin click cluster in water was confirmed by fluorescence titration.