Molecular twist transition in chiral and racemic phospholipid monolayers detected by Maxwell-displacement-current measurements

The physicochemical properties of chiral and racemic phospholipid (alpha-ph osphatidylcholine dipalmitoyl) monolayers at the air-water interface were i nvestigated using Maxwell-displacement-current (MDC) and surface pressure m easurements by monolayer compression. The chiral and racemic phospholipid m onolayers exhibited the same pressure-area isotherm with a pressure plateau at a temperature of 20 degrees C. However, some critical MDC peaks were ge nerated with different amplitude and sign depending on the chirality of the phospholipids in the plateau region. This anomalous MDC generation is theo retically interpreted on the basis of the molecular twist transition induce d by monolayer compression.