X -Ray diffraction and multinuclear solid-state NMR studies of hepatopancreal granules from Helix aspersa and Carcinus maenas

Abstract

Granules isolated from the snail Helix aspersa and the shore crab Carcinus maenas have been studied by using scanning electron microscopy, powder X-ray diffraction and solid-state nuclear magnetic resonance (NMR). These amorphous deposits are largely based on pyrophosphate (P$\_{2}$O$\_{7}{}^{4-}$) and orthophosphate (PO$\_{4}{}^{3-}$) respectively. NMR indicates that water is evenly distributed throughout the pyrophosphate granules and that the PO$\_{4}{}^{3-}$ ions occupy distorted lattice sites. The $^{1}$H NMR spectra of the orthophosphate granules of desiccated and normal deposits indicate that water can move in and out of these solids. This movement is probably facilitated by the organic component, identified by $^{1}$H-$^{13}$C NMR, particularly in the crab granules. The distorted lattice, the presence of hydrated ions and the interactions with the organic matrix probably account for many of the properties of these solids and are relevant to the interpretation of their biological significance.