Chondroitin sulfate
Each monosaccharide may be left unsulfated, sulfated once, or sulfated twice.  In the most common case, the hydroxyls of the 4 and 6 positions of the N-acetyl-galactosamine are sulfated, with some chains having the 2 position of glucuronic acid.  Sulfation is mediated by specific sulfotransferases.  Sulfation in these different positions gives specific biological activities to chondroitin GAG chains.