Reversible Crystal Transition of Guanosine between the Dihydrate and Anhydrous States Coupled with Adsorption-Desorption Process

Abstract

Relative humidity induces the reversible crystal transition of guanosine between the dihydrate and the anhydrous state. The characteristics of the transition was investigated by means of X-ray powder diffraction analysis and high-resolution solid-state 13C NMR spectroscopy. Adsorption-desorption hysteresis was observed. Guanosine dihydrate (the H-state) which is crystallized from an aqueous solution rapidly loses crystal water below 10% relative humidity (rh), and is anhydrous at 0% rh (the A-state). The crystals gradually recover the H-state at approximate 20% rh. In the adsorption process between 10-20% rh, there exists one intermediate state, M, with 1.2-1.3 moles water per mole guanosine. The lattice of the M-state was determined to be orthorhombic with the cell parameters of a = 16.248(1), b = 11.603(1), and c = 13.643(2) A. The base-stacking structure is retained throughout the transition. On the other hand, conformational changes of the riboses and break of the hydrogen-bonding network between the bases would be induced in the A-state in conformity with lack of crystal water.

Dependence of 13C NMR Chemical Shifts on Conformations of RNA Nucleosides and Nucleotides

“…The identity of all three polymorphs was confirmed by X-ray powder diffraction. Polymorph A tends to lose water on storage in the laboratory atmosphere, giving polymorph B; guanosine dihydrate has similarly been observed to dehydrate to anhydrous guanosine (33).…”

Hydration of AMP and ATP Molecules in Aqueous Solution and Solid Films

“…Each form of hydrates is stable in particular RH range and is characterized by a specific spatial arrangement of nucleotide groups and water molecules. Detailed structure of crystalline hydrates of ATP 2− was examined by X-ray diffraction and formation of hydrates with one, two and three water molecules coordinated with the Na + ions, negatively charged oxygen atoms of phosphate groups and polar atoms of the nucleoside and ribose has been revealed [14]. Unfortunately, there are no crystallographic data in literature on hydrates of fully ionized species ATP 4− and AMP 2− most probably due to their inability of crystallization [16].…”

Characteristics of Crystal Transitions Among Pseudopolymorphs

“…16.3.3. We examined this transition using not only X-ray analysis but also Raman spectroscopy and molecular dynamics simulation [16,19,24].…”

“…16.12) [18]. A structural transition occurs between the dihydrate (phase H) and anhydride (phase A) in the region of 20-0 %RH [16,19]. The change in the number of crystal water molecules determined by gravimetric measurements and the X-ray powder (Fig.…”