Effect of deuteration on lipid monolayer phase behaviour as a function of temperature

A biological cell membrane is based on a bilayer of lipid molecules, which form a selective barrier in which functional molecules are embedded. The nature of the lipid constituents is important for the action of these molecules and our research aims to link lipid structure with the properties of the monolayers and bilayers they form. Studies of model systems often employ isotopic labelling to separate signals from different constituents in the model. Deuterium labelling is used in spectroscopic and neutron studies on the assumption that the chemical and physical behaviour of the molecules is unchanged. In this study, we propose to determine the conditions in which the assumption is valid and those in which it is not, using x-rays (which are insensitive to isotopic substitution) as the probe to compare structure of deuterated and undeuterated lipid monolayers at different temperatures. This experiment was conceived as part of a joint Diamond-ISIS proposal, which was awarded by Diamond. The Diamond portion of the experiment has been successfully carried out and here we request time to carry out the neutron reflectivity component of the experiment.