Design and Function of Supramolecular Recognition Systems Based on Guest-Targeting Probe-Modified Cyclodextrin Receptors for ATP

In this study, we have developed a rational design strategy to obtain highly selective supramolecular recognition systems of cyclodextrins (CyDs) on the basis of the lock and key principle. We designed and synthesized dipicolylamine (dpa)-modified γ-CyD–Cu²⁺ complexes possessing an azobenzene unit (<b>Cu·1–</b><i><b>γ</b></i><b>-CyD</b>) and examined how they recognized phosphoric acid derivatives in water. The results revealed that <b>Cu·1–</b><i><b>γ</b></i><b>-CyD</b> recognized ATP with high selectivity over other phosphoric acid derivatives. The significant blue shift in the UV–vis spectra and ¹H NMR analysis suggested that the selective ATP recognition was based on the multipoint interactions between the adenine moiety of ATP and both the CyD cavity and the azobenzene unit in addition to the recognition of phosphoric moieties by the Cu–dpa complex site. Our unique receptor made it capable of distinguishing ATP from AMP and ADP, revealing the discrimination of even a length of one phosphoric group. This study demonstrates that, compared to conventional recognition systems of CyDs, this multipoint recognition system confers a higher degree of selectivity for certain organic molecules, such as ATP, over their similar derivatives

Saccharide Recognition Based on Self-Assembly of Amphiphilic Phenylboronic Acid Azoprobes

We designed amphiphilic phenylboronic acid azoprobes (<b>B-Azo-Cn</b>) and evaluated their saccharide recognition function in relation to the micelle formation changes of the self-assembled <b>B-Azo-Cn</b>. First, we evaluated <b>B-Azo-C8</b> in a 1% methanol–99% water solution under basic conditions. The wavelength of maximum absorption in the ultraviolet–visible (UV–vis) spectra of <b>B-Azo-C8</b> was shifted, and the solution showed a color change with the addition of saccharides. The morphology of <b>B-Azo-C8</b> was evaluated using dynamic light scattering (DLS) measurements and transmission electron microscopy (TEM) observations. <b>B-Azo-C8</b> formed aggregates in the absence of saccharides and in the presence of glucose. In the presence of fructose, micelle-formed <b>B-Azo-C8</b> was dispersed, indicating that <b>B-Azo-C8</b> changed its dispersion state by recognizing fructose. The effect of alkyl chain length on the saccharide recognition ability was examined as well. <b>B-Azo-C4</b> and <b>B-Azo-C12</b> did not recognize saccharides in a 1% methanol–99% water solution under basic conditions, indicating that an appropriate alkyl chain length was required for recognizing saccharides. The control of the hydrophilic–lipophilic balance (HLB) was a key factor for saccharide recognition

Recognition of d‑Glucose in Water with Excellent Sensitivity, Selectivity, and Chiral Selectivity Using γ‑Cyclodextrin and Fluorescent Boronic Acid Inclusion Complexes Having a <i>Pseudo</i>-diboronic Acid Moiety

Fluorescence recognition of d-glucose in water with excellent sensitivity, selectivity, and chiral selectivity is desired because d-glucose is an essential component in biological and pathological processes. We report an innovative approach that exploits the 1:2 stoichiometric inclusion complexes of γ-cyclodextrin (γ-CyD) with two molecules of fluorescent monoboronic acid-based receptors, which form a pseudo-diboronic acid moiety as the recognition site for d-glucose in water. Two monoboronic acids (1F and 2N) were easily synthesized without heating or column purification. The 1:2 stoichiometric inclusion complexes (1F/γ-CyD and 2N/γ-CyD) were prepared in a mixture of dimethyl sulfoxide/water (2/98 in v/v) by mixing γ-CyD and the corresponding monoboronic acids. Both 1F/γ-CyD and 2N/γ-CyD exhibited strong turn-on response to d-glucose with excellent selectivity over nine other saccharides in the water-rich solvent at pH 7.4 owing to the ditopic recognition of d-glucose by the pseudo-diboronic acid moieties. The limits of detection of 1F/γ-CyD and 2N/γ-CyD for d-glucose were 1.1 and 1.8 μM, respectively, indicating the remarkable sensitivity for the detection of d-glucose at μM levels. 1F/γ-CyD and 2N/γ-CyD also demonstrated chiral-selective recognition of d-glucose, which is apparent from the 2.0- and 6.3-fold enhancement of fluorescence by the addition of d-glucose relative to l-glucose addition, owing to the chiral pseudo-diboronic acid moieties produced by the chiral γ-CyD cavity. To the best of our knowledge, 2N/γ-CyD has the highest d/l selectivity among hitherto reported fluorescent diboronic acid-based receptors