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. Author manuscript; available in PMC: 2012 May 14.
Published in final edited form as: Virology. 2009 Dec 11;397(2):389–398. doi: 10.1016/j.virol.2009.11.011

Fig. 1.

Fig. 1

Heparan sulfate modifications. Heparan sulfate chains are initially synthesized as repeating disaccharide units of N-acetylated glucosamine and glucuronic acid. HS can then be modified by a series of enzymatic reactions, including N-deacetylation and N-sulfation of N-acetylated glucosamine converting it to N-sulfo-glucosamine, C5 epimerization of glucuronic acid to iduronic acid, and O-sulfation at the 2-OH, 6-OH, and 3-OH positions. First is 2-O-sulfation of iduronic acid and glucuronic acid, followed by 6-O-sulfation of N-acetylated glucosamine and N-sulfo-glucosamine units, and finally 3-O-sulfation of glucosamine residues. 2-O (red) and 3-O (green) sulfations are highlighted.