Strong Reduction of the Chain Rigidity of Hyaluronan by Selective Binding of Ca2+ Ions

• DOI: 10.1021/acs.macromol.0c02242
• Publication Date: 2021-01-19T06:49:55Z
• Authors: Giulia Giubertoni; Alberto Pérez de ...; Fouzia Bano; Xing Zhang; Robert J. Linhardt; Dixy E. Green; Paul L. DeAngelis; Gijsje H. Koenderink; Ralf P. Richter; Bernd Ensing; Huib J. Bakker
• Keywords: Divalent; Carboxylate; Side chain

The biological functions of natural polyelectrolytes are strongly influenced by the presence ions, which bind to polymer chains and thereby modify their properties. Although impact such modifications is well recognized, a detailed molecular picture binding process mechanisms that drive subsequent structural changes in lacking. Here, we study mechanism condensation calcium, divalent cation, on hyaluronan, ubiquitous human tissues. By combining two-dimensional infrared spectroscopy experiments with dynamics simulations, find calcium specifically binds hyaluronan at millimolar concentrations. Because its large size charge, cation can simultaneously negatively charged carboxylate group amide adjacent saccharide units. Molecular simulations single-chain force measurements provide evidence ions weakens intramolecular hydrogen-bond network increasing flexibility chain. We also observe saturates maximum fraction ∼10-15 mol %. This saturation indicates Ca