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

The binding of Ca2+ to synthetic hexasaccharide 1, containing the structura l 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 Ca2+ binding, and molecular modeling res ults predict three different types of binding sites with different negative potential and preorganized geometry. The presence of Ca2+ does not seem to affect the overall helical structure of hexasaccharide 1, although it seem s to have a marked influence on the flexibility of the oligosaccharide back bone.