Nitrous oxide, N2O, is an inhalant anaesthetic with a long history of use dating back to 1844. It is most commonly used as a light sedative in dentistry, or in child birth and medical emergencies as 50%:50% mixture with oxygen. Despite this long usage the precise mode of action of N2O as a general anaesthetic is not understood. Anaesthetic action is thought to involve specific interactions with protein receptors and yet this seems unlikely for N2O since it will interact only weakly with a protein and must be present at high concentrations. Although changes in membrane dynamics have been discounted as an explanation for anaesthetic action in fact, to date, there are no experimental data on the direct effect of N2O on these dynamics at normal pressures. The aim of the current proposal is thus to investigate whether the dynamics of a phospholipid are modified by the presence of N2O.