Selective binding of zinc ions

The relative binding affinity of Zn2+ to several glycosaminoglycans was determined by gel-filtration chromatography. Binding was observed only between Zn2+ and heparin. No binding was observed between Zn2+ and chondroitin 4-sulphate, chondroitin 6-sulphate, dermatan sulphate or hyaluronic acid. All of the glycosaminoglycans contained carboxy groups, but only heparin bound Zn2+. This observation suggests that, contrary to a previously proposed hypothesis, simple electrostatic interactions between the negatively charged carboxy groups of the glycosaminoglycans and the positively charged Zn2+ cannot explain the observed binding.