Interaction of heparin with Ca2+:: A model study with a synthetic heparin-like hexasaccharide

The binding of Ca(2+) to synthetic hexasaccharide 1, containing the structural motifs of the regular region of heparin, has been investigated using NMR spectroscopy and molecular modeling. The NMR data of the calcium salt of 1 indicate the existence of specific Ca(2+) binding, and molecular modeling results predict three different types of binding sites with different negative potential and preorganized geometry. The presence of Ca(2+) does not seem to affect the overall helical structure of hexasaccharide 1, although it seems to have a marked influence on the flexibility of the oligosaccharide backbone.