Analysis of Maxwell displacement current generated from chiral phospholipid monolayers

The Maxwell-displacement-current measurement (MDC) and surface pressure of chiral, racemic and their mixture of phospholipid [α-phosphatidylcholine dipalmitoyl (DPPC)] monolayers at the air–water interface by monolayer compression were performed. Some critical MDC peaks were generated with different amplitude and sign depending on the chirality of the phospholipids in the plateau region. Using a model based on the Bragg–Williams theory for binary mixtures, the contribution of the mixing effect to the generation of MDC is analyzed. It is revealed that the formation of the homogeneous and intimate mixture of the left- and right-handed chiral enantiomers gives rise to the additional MDC generation due to the dipole–dipole interaction between the left- and right-handed chiral enantiomer molecules by the molecular twist transition during monolayer compression.