Structural rearrangement of chitin molecular sheets in water mechanism of structural formation of regenerated chitin proposed by molecular dynamics simulation

Abstract

Structural rearrangement of chitin molecular sheets with four tetramers along (110) and (020) crystal planes of a-chitin in water was studied by molecular dynamics simulation in order to identify the first structure in course of crystallization. Hydrogen bonded molecular sheet along (110) plane changed into van der Waals associated molecular sheet ; and molecular sheet along (020) plane, which was van der Waals associated molecular sheet, remained unchanged. Both calculated molecular sheets had almost similar structures in view of highly developed hydrogen bonding system, molecular conformation and tilt angle of N-acetyl-D-glucosamine ring. In addition, it is natural that reorganized chitin sheet formed by van der Waals forces is structurally stable in aqueous medium due to its hydrophilic surface and hydrophobic inside. Therefore, formation of chitin crystal in an aqueous medium probably starts from the molecular sheet formed by van der Waals forces.