Single-Helical Structure of Native Curdlan and its Aggregation State

ABSTRACT One of the polymorphs of β-(1→3) glucan, curdlan, was studied by X-ray diffraction and thermal analyses. Different from the molecular models proposed so far, the molecular structure of native curdlan (Form I) was found to be a 6/1-single stranded helix. Therefore, the transformation from Form I to Form II is a conversion process from single to triple. Form I specimen has three kinds of water, bound- and amorphous-water in the crystalline micelles and free water in the intermicelles. The amount of bound water is estimated to be more than 10 %wt. If the specimen is kept at less than 98%RH, the effusion of free water and amorphous water occurs very easily, which causes a drastic decrease of the specimen weight. The bound water is left even at 0%RH.