Ethanol plays an important role in the human metabolism. It is in particular known to act as a drug enhancer by increasing trans-membrane permeability, and as an anesthetic. However, the molecular mechanism behind these functionalities remains largely unknown. In this combined proposal we propose to study molecular structure and dynamics of a lipid membrane containing ethanol. Position and partitioning of ethanol and water molecules will be determined from reflectivity measurements using OFFSPEC. In-plane and trans-membrane dynamics will be determined using the unique capabilities of LET. By using solid supported, highly oriented membranes, we will be able to measure in-plane and trans-membrane diffusive and transport dynamics in-situ, under physiological conditions. Deuterium labeling will be used to emphasize ethanol, water and lipid molecules.