Influence of the Molecular Weight and the Presence of Calcium Ions on the Molecular Interaction of Hyaluronan and DPPC.

Thomas Zander,D C Florian Wieland,Krzysztof Górny,Per M Claesson,Piotr Bełdowski,Andra Dédinaité,Zbigniew Dendzik,Vasil M Garamus,Regine Willumeit-Römer

doi:10.3390/molecules25173907

Abstract

Hyaluronan is an essential physiological bio macromolecule with different functions. One prominent area is the synovial fluid which exhibits remarkable lubrication properties. However, the synovial fluid is a multi-component system where different macromolecules interact in a synergetic fashion. Within this study we focus on the interaction of hyaluronan and phospholipids, which are thought to play a key role for lubrication. We investigate how the interactions and the association structures formed by hyaluronan (HA) and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) are influenced by the molecular weight of the bio polymer and the ionic composition of the solution. We combine techniques allowing us to investigate the phase behavior of lipids (differential scanning calorimetry, zeta potential and electrophoretic mobility) with structural investigation (dynamic light scattering, small angle scattering) and theoretical simulations (molecular dynamics). The interaction of hyaluronan and phospholipids depends on the molecular weight, where hyaluronan with lower molecular weight has the strongest interaction. Furthermore, the interaction is increased by the presence of calcium ions. Our simulations show that calcium ions are located close to the carboxylate groups of HA and, by this, reduce the number of formed hydrogen bonds between HA and DPPC. The observed change in the DPPC phase behavior can be attributed to a local charge inversion by calcium ions binding to the carboxylate groups as the binding distribution of hyaluronan and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine is not changed.

Highlights

Hyaluronan (HA) is one of the important physiological bio macromolecules which is ubiquitous in the body
We decided to use HA of 10 kDa and 1500 kDa for small angle neutron scattering (SANS) measurements as this study focused on the formed structures and the structural arrangement of DPPC and HA to elucidate if the observed changes in the differential scanning calorimetry (DSC) could be attributed to a changed phospholipid packing
This study elucidates the molecular interactions between HA and DPPC to shed light on the synergistic interactions and adds to the understanding of the underlying interaction principles of two of the main synovial fluid components

Summary

Introduction

Hyaluronan (HA) is one of the important physiological bio macromolecules which is ubiquitous in the body. The reason for the interest in the working mechanisms of the synovial joints is due to their excellent lubrication properties with friction coefficients as low as 0.002–0.006 under high shear and load conditions [3,5]. The secret of this performance is thought to be a fluid water layer in between the sliding surfaces and friction reduction occurs via hydration repulsion generated by water interacting with biomolecules adsorbed from the synovial fluid to the cartilage surface, e.g., lubricin, phospholipids and HA [4,6,7,8,9]. The question arises how the association structures adapt to stable well-defined structures that promote a bond but yet retain a fluid and sheared layer of water under high loads and shear conditions

Methods

Results

Discussion

Conclusion