Thermally reversible hydration of beta-chitin.
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.
Saito
Yukie
Y
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
Kumagai
Hiroko
H
Wada
Masahisa
M
Kuga
Shigenori
S
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
D014867:Water; D002686:Chitin