betadex and adamantanecarboxylic-acid

A novel beta-cyclodextrin derivative 1 bearing 8-hydroxyquinolino and triazole groups was synthesized in satisfactory yield by 'click chemistry'. With a good water solubility up to 0.03 mol/L, 1 exhibited an effective switch-on fluorescence response to Cd(2+) over other common metal ions under physiological conditions. Studies on the recognition mechanism indicated that the cooperative coordination of Cd(2+) with both the 8-hydroxyquinolino moiety excluded from the beta-CD cavity and the triazole moiety was a crucial and basic factor to achieve the fluorescent sensing process. Significantly, spectrophotometric studies also demonstrated that, after inclusion complexation with 1-adamantanecarboxylic acid sodium salt (AdCA), the resultant 1/AdCA system gave a more effective fluorescent sensing to Cd(2+) through a cyclodextrin/substrate/Cd(2+) triple binding mode.

Topics: Adamantane; beta-Cyclodextrins; Fluorescent Dyes; Magnetic Resonance Spectroscopy; Quinolizines; Spectrometry, Fluorescence; Spectrometry, Mass, Electrospray Ionization

Beta-cyclodextrin (beta-CD)-functionalized CdSe/ZnS quantum dots (QDs) are used for optical sensing and chiroselective sensing of different substrates using a fluorescence resonance energy transfer (FRET) or an electron transfer (ET) mechanisms. The FRET between the QDs and Rhodamine B incorporated in the beta-CD receptor sites is used for the competitive analysis of adamantanecarboxylic acid and of p-hydroxytoluene. Also, the dye-incorporated beta-CD-modified QDs are used for the chiroselective optical discrimination between D,L-phenylalanine and D,L-tyrosine. The receptor-functionalized QDs are also implemented for the optical detection of p-nitrophenol using an ET quenching route.

Topics: Adamantane; beta-Cyclodextrins; Cadmium Compounds; Electron Transport; Fluorescence Resonance Energy Transfer; Phenylalanine; Quantum Dots; Selenium Compounds; Stereoisomerism; Sulfides; Toluene; Tyrosine; Zinc Compounds

A new fluorescent cyclodextrin shows unexpected and strong fluorescence enhancement upon binding of organic molecules, and the enhancing mechanism is found to be different from those reported in the literature.

Topics: 1-Naphthylamine; 1-Octanol; Adamantane; beta-Cyclodextrins; Circular Dichroism; Deoxycholic Acid; Fluorescent Dyes; Magnetic Resonance Spectroscopy; Models, Molecular; Naphthalimides; Quinolones; Spectrometry, Fluorescence; Structure-Activity Relationship

Using microcalorimetry, we follow changes in the association free energy of beta-cyclodextrin (CD) with the hydrophobic part of adamantane carboxylate (AD) due to added salt or polar (net-neutral) solutes that are excluded from the molecular interacting surfaces. Changes in binding constants with solution osmotic pressure (water activity) translate into changes in the preferential hydration upon complex formation. We find that these changes correspond to a release of 15-25 solute-excluding waters upon CD/AD association. Reflecting the preferential interaction of solute with reactants versus products, we find that changes in hydration depend on the type of solute used. All solutes used here result in a large change in the enthalpy of the CD-AD binding reaction. In one class of solutes, the corresponding entropy change is much smaller, while in the other class, the entropy change almost fully compensates the solute-specific enthalpy. For many of the solutes, the number of waters released correlates well with their effect on air-water surface tensions. We corroborate these results using vapor pressure osmometry to probe individually the hydration of reactants and products of association, and we discuss the possible interactions and forces between cosolute and hydrophobic surfaces responsible for different kinds of solute exclusion.

Topics: Adamantane; beta-Cyclodextrins; Calorimetry; Osmotic Pressure; Thermodynamics; Water

The hydrogen-bond network in mono-altro-beta-cyclodextrin and in its inclusion complex with adamantane-1-carboxylic acid were investigated by (1)H NMR spectroscopy using the chemical shifts, temperature coefficients and vicinal coupling constants of the exchangeable hydroxy protons. The chemical shifts of the 3-OH signals indicated that the hydrogen-bond network between the 2-OH and 3-OH groups was disturbed not only on each side of the altrose residue, but also along the whole dextrin chain. Upon addition of adamantane-1-carboxylic acid, altrose underwent a conformational change from the (1)C(4) to the (O)S(2) form, allowing a more continuous belt of hydrogen bonding, as evidenced by the downfield shift experienced by the 3-OH proton signals of the glucose residues.

Topics: Adamantane; beta-Cyclodextrins; Hydrogen Bonding; Magnetic Resonance Spectroscopy; Molecular Conformation; Protons

Among the different experimental strategies available in capillary electrophoresis (CE) to determine binding parameters, affinity capillary electrophoresis (ACE) has been the most widely embraced due to its easiness of implementation and of data handling. Ligand-substrate binding constants are thus directly derived from the substrate migration time shifts resulting from the variation of ligand concentration introduced in a background electrolyte. Classically, the substrate migration time is measured on top of the electrophoretic peak, assuming symmetrical peak shape. Depending on both substrate and ligand concentrations that may be required to meet detection sensitivity or complexation conditions, zonal migrations in ACE may, however, produce triangular peak shape, most often due to pronounced electromigration dispersion (EMD), and this may result in positively or negatively erroneous migration time assessments. In this work, EMD distorted triangular peak shapes obtained in the course of host-guest complexation studies were fitted with the Haarhoff-Van der Linde function, allowing better estimation of migration time. The model systems studied were those of beta-cyclodextrin and naproxen, 2-naphthalenesulfonate, or 1-adamantanecarboxylate. The impact of this correction on binding isotherms and binding constant evaluation was exemplified. Furthermore, in situations where the substrate concentration injected by far overtakes that of the ligand in the electrolyte, the interest in this peak shape correction was discussed in connection with the question of whether the free ligand concentration can be still considered equal to the ligand concentration introduced, a question that still remains under debate nowadays.

Topics: Adamantane; beta-Cyclodextrins; Electrolytes; Electrophoresis, Capillary; Models, Chemical; Naphthalenesulfonates; Naproxen