title: Effect of calcium on structure and function of a hyaluronic acid matrix: carbon-13 nuclear magnetic resonance analysis and the diffusional behavior of small solutes.
abstract: Natural-abundance (13)C NMR at 25.16 MHz has been used to study a 2.5% matrix of hyaluronic acid at various degrees of polymerization and at various ionic strengths. Peak assignment is facilitated by comparing proton-decoupled and off-resonance-decoupled spectra of a hyaluronidase-depolymerized matrix with spectra from relevant monosaccharides. In contrast to the spectrum following depolymerization, the spectrum for intact matrix has considerable broadening, particularly for peaks assigned to the N-acetylglucosamine moiety. This is most dramatic for the hydroxymethylene carbon. With the addition of Ca(2+) above 5 mM these broadened peaks narrow and approach the sharpness observed for the hyaluronidase digest. There is no shift in resonance peak positions. These changes are quantitatively less impressive if Na(+) is substituted for Ca(2+). The data suggest the existence of a considerable degree of order in regions of the matrix at physiological concentrations of Ca(2+). Within such a matrix the translational movement of lysine and glucose is enhanced relative to that in a matrix of agarose. Further addition of Ca(2+) abrogates not only matrix order, but the enhanced diffusivity as well.
mesh_terms: D002118:Calcium / Q000494:pharmacology*; D004058:Diffusion; D005947:Glucose; D006801:Humans; D006820:Hyaluronic Acid; D008239:Lysine; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation / Q000187:drug effects; D009994:Osmolar Concentration
chemical_list: D006820:Hyaluronic Acid; D005947:Glucose; D008239:Lysine; D002118:Calcium