Conformationally mobile glucosylthioureido-calix[6]- and calix[8]arenes: synthesis, aggregation and lectin binding

Two new glucoclusters 2a and 2b, in which the sugar units are connected to the upper rim of methoxycalix[6]- and calix[8]arene derivatives via thiourea linkages, were synthesised and their aggregation properties in water studied by (1)H NMR, atomic force microscopy and dynamic light scattering. Small size aggregates (2-10nm diameter) are formed by both macrocycles, which become much larger (200-300nm) in the presence of a phosphate buffer, whereas other anions (Cl(-), NO(3)(-), SO(4)(-)) have no effect. The glycoclusters 2a and 2b interact with plasmid DNA but do not condense it, while in the presence of a glucose-specific lectin such as Concanavalin A (ConA) agglutination occurs. The data obtained give useful insights into the mode of binding of calixarene-based glycoclusters with lectins.