A comparison of biological and calorimetric analyses of multivalent glycodendrimer ligands for concanavalin A

The cluster glycoside effect - the observation that multivalent glycosides bind to their polyvalent protein receptors with apparent affinities greater than those that can be rationalized solely on the basis of valency - is by now a well established phenomenon. As part of a continuing effort to provide a molecular basis for the cluster glycoside effect, we report here the synthesis of two series of mannosylated dendritic ligands and their performance in a range of competitive and non-competitive binding assays, including hemeagglutination inhibition (HIA), enzyme-linked lectin assays (ELLA) and isothermal titration microcalorimetry (ITC). The first series of ligands contained a semi-rigid glycylglycine spacer and showed no significant performance enhancement in any binding studies. The second series of ligands contained a flexible tetraethylene glycol spacer; these ligands showed marked enhancements at tetravalent and hexavalent levels in both HIA (IC50=3 and<0.8 μM, respectively) and ITC (K(A)=6.2x104 and 1.5x106 M-1, respectively) studies. In all cases, the thermodynamic parameters of association are consistent with non-specific aggregation rather than enhanced lectin-ligand affinity. This conclusion is reinforced by the lack of enhancements in ligand activity observed in ELLA studies. Copyright (C) 2000 Elsevier Science Ltd.

Duke Scholars

Author Eric John Toone Chemistry