Organisms which live in the presence of large quantities of salt are known as halophilic (meaningsalt-loving). Halophilic proteins are of great interest due to their ability to remain soluble, flexibleand functional under highly saline conditions, suggesting a delicate balance between theintermolecular interactions of the protein, ions and solvent. The most common feature of halophilicproteins is that they contain a large number of acidic residues. A comprehensive and systematicinvestigation is required which examines the intermolecular interactions between acidic residues,ions and water at the ion concentrations relevant to halophilic protein adaption. Obtainingstructural insight of this system from neutron diffraction is a crucial step in understanding halophilicsystems on the molecular level, and will provide a benchmark for future studies.