Reversible Crystal Phase Change between Guanosine Dihydrate and Anhydrous Guanosine by a Heating-Cooling Process

In this work, the reversible dehydration/hydration process of guanosine dihydrate was studied in detail by a simple heating/cooling process through in situ characterizations such as varying temperature-powder X-ray diffraction (VT-PXRD) and polarizing optical microscopy. Two novel hydrated phases of guanosine, hydrated guanosine I and II phases, were found and characterized in detail for the first time. We found that the reversible crystal phase changes between guanosine dihydrate and anhydrous guanosine contained continuous and discontinuous crystal lattice changes. The four phases of guanosine had similar crystal lattice parameters and there were no obvious changes in varying the temperature of the polarizing optical microscope among the phase change processes. The dehydration/hydration processes of inosine dihydrate and guanine monohydrate were furthered studied and compared with that of guanosine dihydrate. We found that the guanine monohydrate and guanosine dihydrate can keep the structure of the water channels and their own reversible dehydration/hydration processes. In comparison, the dehydration of inosine dihydrate was an irreversible process and anhydrous inosine was very stable and could not transform to inosine dihydrate.