Dynamics of cello-oligosaccharides on a cellulose crystal surface

Molecular dynamics (MD) simulations were performed to study the dynamics of cello-oligosaccharides on the cellulose crystal surface in the presence of water. In particular, single chains of cello-oligomers containing 2-10 repeat units, i. e. cellobiose, cellotetraose, cellohexaose, cellooctaose as well as cellodecaose-were simulated separately on the (1,0,0) cellulose crystal surface. The dynamics of cello-oligosaccharides were characterized as a function of the distance from the cellulose crystal surface. When the initial location of the cello-oligosaccharides was in the vicinity of the cellulose crystal (separation distance ~4-5Å), they exhibited very small changes in their location and conformation. The cello-oligosaccharides with initial positions far from the surface moved either towards or away from the surface, as would be expected for diffusive behavior. However, once these molecules came in contact with the cellulose crystal surface, they became effectively immobile and got adsorbed on the surface. The dynamics of cellodecaose were studied in detail. From several MD trajectories, three stable conformations for the alignment of cellodecaose on the crystal surface were identified. These are: chain axis of cellodecaose is aligned parallel to the axes of the chains on the crystal surface, chain axis is approximately at right angles to the axes of the chains on the surface, and an obtuse angle conformation in which part of the chain is parallel and the other part is at an angle to the axes of the chains on the surface. The mechanism of adsorption of the cellodecaose on the surface was also identified.