Effect of dodecyl dimethyl phosphine oxide penetration into phospholipid monolayers: morphology and dynamics

The penetration kinetics of dodecyl dimethyl phosphine oxide (C12DMPO) into a Langmuir monolayer of dipalmitoylphosphatidylcholine (DPPC) and the corresponding morphology were experimentally studied. It was found that under proper conditions the penetration of dodecyl dimethyl phosphine oxide could induce a first-order phase transition in the fluid-like lipid Langmuir monolayer. The transition is indicated by a break point in the Π(t) penetration kinetics curves and can be visualized by BAM. The dynamics of the penetrated layer and the subphase effect on the Langmuir monolayer were also investigated. The experimental results show that the adsorption of soluble molecules increases the surface density, which in turn causes the first-order phase transition in the monolayer. When the surface density reaches a certain critical value, the main phase transition sets in.