Montmorillonite Clay (MTM) combined with a biological polymer xyloglucan (XG) is a novel bio-nanocomposite material developed recently. Based on its bio-degradability, one has anticipated a wide range of applications in the paper making industry, in the environmental remediation area as well as in the biomedical field. In the present work a molecular dynamics (MD) simulation approach is employed to investigate the details of XG adsorption onto an MTM surface at the atomic level. Aiming at the adsorption mechanism and conformational properties of XGs, two polymer fragments characterized as Native XG (GXXLGXXXG) and Modified XG (GXXXGXXXG) interacting with the MTM surface were built up both in an explicit water model and in vacuo. Here G denotes an unsubstituted �-D-Glcp unit, X a a-D-Xylp-(1-6)-�-D-Glcp-(1-4) and L a �-D(1-2)-Galp(1-2)-a-D-Xylp-(1-6)- �-D-Glcp-(1-4) unit. Our work indicates that in either phase the electrostatic interaction plays a central role of the adsorption process. The existence of water mediates the formation of hydrogen bonds between the XGs molecules and the MTM surface. Moreover, it is predicted that both XGs prefer a orientation parallel to [100] to adsorb onto the MTM surface and that the native XG exhibits higher interaction energy and binding affinity than the modified one. The variation of L in the side chain of XGs shows no significant influence in the view of free energy and entropy change, while it gives conformational suggestions which indicate that an extension of the side chain could facilitate the adsorption interaction of XG/MTM both on the backbone and the side chain residues. All in all, atomistic level theoretical studies of XG/MTM of this kind hold the promise for detailed learning of the adsorption mechanisms and aids the organization of lab experiments for further improvement.

Molecular dynamic simulations of xyloglucan adsorbed onto Na-montmorillonite clay: Exploration of interaction mechanisms and conformational properties

246th National Meeting (2013)

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