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 corr esponding morphology were experimentally studied. It was found that under p roper conditions the penetration of dodecyl dimethyl phosphine oxide could induce a first-order phase transition in the fluid-like lipid Langmuir mono layer. The transition is indicated by a break point in the Pi(t) penetratio n kinetics curves and can be visualized by BAM. The dynamics of the penetra ted layer and the subphase effect on the Langmuir monolayer were also inves tigated. The experimental results show that the adsorption of soluble molec ules increases the surface density, which in turn causes the first-order ph ase transition in the monolayer. When the surface density reaches a certain critical value, the main phase transition sets in. (C) 2000 Elsevier Scien ce B.V. All rights reserved.