Binding of dipeptides and tripeptides containing lysine or arginine by p-sulfonatocalixarenes in water:: NMR and microcalorimetric studies

The water soluble p-sulfonatocalix[n]arenes (n = 4, 6 and 8) (1(4), 1(6) and 1(8)) show glycosylaminoglycan (GAG) mimicry, being both active antithrombotics and modulators of lysyloxidase activity. In order to understand how these synthetic receptors interact with GAG receptor sequences, we have undertaken a study to thermodynamically characterize the binding of dipeptides and tripeptides bearing lysine or arginine residues by 1(4), 1(6) and 1(8) in aqueous buffer at pH 8.0 and 298.15 K. The association constants, enthalpies and entropies of complexation have been determined using titration microcalorimetry. The structure of the complexes in solution has been studied by H-1 NMR spectroscopy. Combining the microcalorimetric data, the binding shifts and the 2D experiments, the nature of the complexation may be clarified.