Effect of pressure on slit channels in guanine sodium salt hydrate: a link to nucleobase intermolecular interactions
The crystal structure of a hydrate of the sodium salt of guanine (2Na+·C5H3N5O2−·7H2O) was studied using single-crystal X-ray diffraction and Raman spectroscopy up to ∼2.5 GPa, after which the structure distorted and the diffraction pattern from single crystal fragments disappeared along with the appearance of powder ring fragments. On increasing the pressure the distances between the double walls of the slit channels formed by the guanine moieties became more equal, with the longer one shortening and the shorter one expanding. The topology of the Na+–water intra-channel infinite clusters was preserved, although these clusters became distorted on compression. Among several types of OH⋯O and OH⋯N hydrogen bonds, only two practically did not change with increasing pressure, namely the bonds connecting the guanine walls to the intra-channel water molecules. A possible relationship to the interactions in the ion channels with the walls formed by the guanine species in biological systems is discussed.