title: Thermally reversible hydration of beta-chitin.
abstract: Thermally induced transition between anhydrous and hydrated forms of highly crystalline beta-chitin was studied by differential thermal calorimetry (DSC) and X-ray diffraction. DSC of wet beta-chitin in a sealed pan gave two well-defined endothermic peaks at 85.2 and 104.7 degrees C on heating and one broad exothermic peak at between 60 and 0 degrees C on cooling. These peaks were highly reproducible and became more distinct after repeated heating-cooling cycles. The X-ray diffraction pattern of wet beta-chitin at elevated temperature showed corresponding changes in d-spacing between the sheets formed by stacking of chitin molecules. These phenomena clearly show that water is reversibly incorporated into the beta-chitin crystal and that the temperature change induces transitions between anhydrous, monohydrate, and dihydrate forms. The DSC behavior in heating-cooling cycles, including reversion between the two endothermic peaks, indicated that the transition between monohydrate and dihydrate was a fast and narrow-temperature process, whereas the one between the anhydrous and the monohydrate form was a slow and wide-temperature process.
authors: Graduate School of Agricultural and Life Sciences, The University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo 113-8657, Japan. aysaito@mail.ecc.u-tokyo.ac.jp
authors: Yukie
authors: Y
authors: Saito
authors: Hiroko
authors: H
authors: Kumagai
authors: Masahisa
authors: M
authors: Wada
authors: Shigenori
authors: S
authors: Kuga
mesh_terms: D000042:Absorption; D000818:Animals; D002152:Calorimetry, Differential Scanning; D002686:Chitin / Q000378:metabolism*; D003460:Crystallization; D007448:Invertebrates / Q000737:chemistry; D013696:Temperature; D014867:Water / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D014867:Water; D002686:Chitin