Pivotal functions of glycosaminoglycan (GAG) 1 side chains of proteoglycans (PGs), especially heparan sulfate (HS), have been implicated in biological processes such as cell adhesion, proliferation, and differentiation and tissue morphogenesis (1). Chondroitin sulfate (CS) and dermatan sulfate (DS) are also found ubiquitously in the extracellular matrices and at cell surfaces, being main components of cartilage and skin, respectively. CS consists of repeating disaccharide units of -4Gl-cUA1-3GalNAc1-, whereas DS is an isomeric form of CS and is formed from precursor CS through the action of glucuronyl C5 epimerase, thus consisting of disaccharide units of -4Gl-cUA1-3GalNAc1-and -4IdoUA␣1-3GalNAc1-in varying proportions (2). These disaccharide units are modified during chain elongation by specific sulfotransferases at C-2 of GlcUA/ IdoUA and/or C-4 and/or C-6 of GalNAc in various combinations, producing characteristic sulfation patterns critical for binding to various functional proteins displaying enormous structural diversity, comparable with that of HS, by embedding multiple overlapping functional sequences (3). Sulfation profiles of GAGs change during development (4, 5). Growing evidence indicates the involvement of CS and DS in the signaling of various heparin-binding growth factors and cytokines (6 -8).We and others have shown the importance of this class of molecule, from simple chondroitin involved in cell division of a nematode (9) to differentially oversulfated CS-D and CS-E involved in neuroregulatory functions (10 -12) and the binding of growth factors in mammalian systems (13). While pursuing the critical structural elements in the CS variants, we became *