The cellobiose structures with global minimum potential energy in vacuum and water: LMOD optimization method

To understand the structure of cellulose, we searched for the global minimum potential energy of cellobiose, a basic structural unit of cellulose, in vacuum and water. We used the Low-MODe (LMOD) optimization method in the Ambertools1.5 package with aGLYCAM-06 force field. The generalized Born model proposed by Hawkins, Cramer, and Trühlar was used as a solvation model. The global minima in vacuum and water had different conformations. These differences were explained by solvation effects, especially the change in electrostatic interaction upon solvation. The global minimum in vacuum was determined by the strength of hydrogen bonding, which was reduced in water. The conformation, which was subject to electrostatic repulsion in vacuum, became the global minimum in water because the electrostatic repulsion decreased as a result of the attractive interaction with water.