Proteoglycans(PGs)and glycosaminoglycansGAGs a proteoglycan is a poly peptide chain(proteo) with polysaccharide(glycan or GAG)side chains Primary structure modeled as an alternating copolymer of two different glucose-like units, one of them an acidic sugar-like molecule the other an amino sugar with a negatively charged sulfate group (except hyaluronic acid that is not sulfated) Electrostatic interactions between charged groups in GAG side chains of PG responsible for about 50% of stiffness of articular cartilage(Grodzinsky et al.)Proteoglycans (PGs) and glycosaminoglycans (GAGs) • A proteoglycan is a polypeptide chain (proteo) with polysaccharide (glycan or GAG) side chains. • Primary structure modeled as an alternating copolymer of two different glucose-like units, one of them an acidic sugar-like molecule, the other an amino sugar with a negatively charged sulfate group (except hyaluronic acid that is not sulfated). • Electrostatic interactions between charged groups in GAG side chains of PG responsible for about 50% of stiffness of articular cartilage (Grodzinsky et al.). 7