Characterization of cellulose molecules in bio-system studied by modeling methods

Cellulose chains in bio-system were examined. A model system, in which molecular chains were fixed at one end in an aqueous environment, was analyzed as a model bio-system of cellulose. Five cellulose chains (DP = 40), whose one end was fixed (like a cantilever), were placed in 20.0 × 2.8 × 2.8 nm3 cell which was filled up with water molecules. This model cell was thoroughly annealed and then piled up three-dimensionally. The molecular dynamics simulation was applied to this model system at room temperature (298 K) with time step of 1.0 femto-second in AMBER force field with parameter sets for carbohydrates. The molecular motion of cellulose chains in cantilever condition was found to be more moderate compared with case of free chains. The water molecules around the cellulose chains were interrupted directly forming hydrogen bondings among the cellulose chains. This result suggests that degree of crystallinity of cellulose in bio-system is low. The result also reminds us that the cellulose chains are originally able to hold water molecules giving them a gel property, although dried cellulose is not soluble in water.