Thermodynamic properties of mixtures of deuterated and undeuterated dipalmitoyl phosphatidylcholines (differential scanning calorimetry/lipid bilayers/membranes)

In need for nonperturbing but spectroscopically unique environments for studies of lipid/lipid and lipid/protein interactions, we have investigated the thermodynamic properties of deuterated and undeuterated dipalmitoyl phosphatidylcholines as well as the mixtures of both. The data have been collected using the highly sensitive differential scanning calorimetry. From the results of these measurements we conclude that mixtures of deuterated and undeuterated lipids behave ideally. The transition enthalpies, transition entropies and the cooperative unit are given as a function of the input ratio of the components and the phase diagram is constructed, showing that the deuterated lipids are suitable as nonperturbing probes.