On the Conformational Properties of Amylose and Cellulose Oligomers in Solution

Molecular dynamics (MD) simulations were used to monitor the stability and conformation of double-stranded and single-stranded amyloses and single-stranded cellulose oligomers containing 9 sugar moieties in solution as a function of solvent composition, ionic strength, temperature, and methylation state. This study along with other previous studies suggests that hydrogen bonds are crucial for guaranteeing the stability of the amylose double helix. Single-stranded amylose forms a helical structure as well, and cellulose stays highly elongated throughout the simulation time, a behavior that was also observed experimentally. In terms of coordination of solute hydroxyl groups with ions, amylose shows entropy-driven coordination of calcium and sulfate ions, whereas cellulose-ion coordination seems to be enthalpy-dominated. This indicates that entropy considerations cannot be neglected when explaining the structural differences between amyloses and celluloses.