title: Calcium destabilizes and causes conformational changes in hyaluronic acid.
abstract: The physical properties of proteoglycans found in the extracellular matrix influence the behavior of resident macromolecules, micro-ions, and cells. The forces stabilizing structured regions of hyaluronic acid (HA), a major component of extracellular matrix, were measured. The free energy of stability associated with structured regions within human HA was determined by potentiometric titration. A plot of free energy versus temperature demonstrated that the secondary structure was most stable at 25 degrees C and was destabilized at temperatures near 50 degrees C. In the presence of 5 mM CaCl2, the free energy of stability of the structured regions was reduced by 30 cal/mole. Classical light scattering and viscosity measurements confirmed the impact of calcium on HA. CaCl2 (5 mM) reduced the radius of gyration of HA. Above concentrations of 3 mM calcium, the viscosity of 0.1% HA solutions was reduced sharply. The ability of cells to secrete calcium, combined with the exquisite sensitivity of HA to calcium, may permit cell-mediated modification of the extracellular matrix and thus may facilitate cell motility.
authors.affiliation: Center for Thrombosis and Hemostasis, Lineberger Cancer Research Center, U.N.C. School of Medicine, Chapel Hill.
authors.forename: D A
authors.initials: DA
authors.lastname: Gabriel
authors.forename: M E
authors.initials: ME
authors.lastname: Carr
mesh_terms: D002118:Calcium / Q000494:pharmacology*; D006801:Humans; D006820:Hyaluronic Acid; D008027:Light; D008968:Molecular Conformation; D011199:Potentiometry; D012542:Scattering, Radiation; D014783:Viscosity
chemical_list: D006820:Hyaluronic Acid; D002118:Calcium