The Nature and Origin of Chemical Shift for Intracellular Water Nuclei in Artemia Cysts

We investigated the possible existence of chemical shift of water nuclei in Artemia cysts using high resolution nuclear magnetic resonance (NMR) methods. The results conducted at 60, 200, and 500 MHz revealed an unusually large chemical shift for intracellular water protons. After correcting for bulk susceptibility effects, a residual downfield chemical shift of 0.11 ppm was observed in fully hydrated cysts. Similar results have been observed for the deuterium and ¹⁷O nuclei.

We have ruled out unusual intracellular pH, diamagnetic susceptibility of intracellular water, or interaction of water molecules with lipids, glycerol, and/or trehalose as possible origins of the residual chemical shift. We conclude that the residual chemical shift observed for water nuclei (¹H, ²H, and ¹⁷O) is due to significant water-macromolecular interactions.