Binding affinity properties of dendritic glycosides based on a β-cyclodextrin core toward guest molecules and concanavalin A

The inclusion behavior and concanavalin A binding properties of hepta-antennated and newly synthesized tetradeca-antennated C-6-branched mannopyranosyl. and glueopyrannosyl cyclomalto-heptaose (beta -cyclodextrin) derivatives have been evaluated by isothermal titration microcalorimetry and enzyme-linked lectin assay (ELLA), respectively. The synthesis of three first-order dendrimers based on a beta -cyclodextrin core containing 14 1-thio-beta -D-glucose, 1-thio-beta -mannose, and 1-thio-beta -rhamnose residues was performed following a convergent approach and involving (1) preparation of a thiolated bis-branched glycoside building block and (2) attachment of the building block onto heptakis(6-deoxy-6-iodo)-beta -cyclodextrin. Calorimetric titrations performed at 25 degreesC in buffered aqueous solution (pH 7.4) gave the affinity constants and the thermodynamic parameters for the inclusion complex formation of these beta -cyclodextrin derivatives with guests sodium 8-anilino-1-naphthalensulfonate (ANS) and 2-naphthalenesulfonate. The host capability of the persubstituted beta -cyclodextrins decreased with, respect to the native beta -CD when sodium 2-naphthalenesulfonate was used, as a guest and improved when ANS was used as a guest molecule. Heptavalent mannoclusters based on beta -CD cores enhance the lectin binding affinity due to the cluster effect; however, the increase of the valency from 7 to 14 ligands did not contribute to the improvement of the concanavalin A binding affinity. In addition, the synthesized hyperbranched mannoCDs lost completely the capability as a host molecules.