Structural stability of the solvated cellulose III_I crystal models: a molecular dynamics study

Molecular dynamics (MD) simulations of cellulose III_I crystal models have been carried out. The crystal models were composed by either 24 or 48 cellooligomers consisting of either 20 or 40 residues and were surrounded by waters in a periodic boundary box. Two base plane types differing in a constituent crystal lattice plane, (0 −1 0) × (0 1 0) and (1 0 0) × (0 1 0), were additionally considered. Among the resulting eight crystal models, an overall structure conversion was observed for the seven models. The final structures had a triclinic-like chain arrangement involving one-quarter staggering chains with respect to its axis. The successive, local transformation involving cooperative bends in cellooligomers was observed during the structure conversion. Only the 48 × 20-mer model having the (0 −1 0) lattice plane retained the original crystal structure throughout a 2.5-ns simulation. The MD simulations with an implicit solvent system and a vacuum system were also performed to asses a solvent effect on the structure conversion.