INTERACTION OF DPPC MONOLAYERS WITH SOLUBLE SURFACTANTS - ELECTROSTATIC EFFECTS OF MEMBRANE PERTURBANTS

We studied the effects of four soluble surfactants on DPPC monolayers to elucidate the action of these membrane perturbants. The presence of nonionic N-9 and amphoteric C31G strongly affected the pure DPPC isot herm, while anionic SDS and cationic DTAB had little effect. The impac t of surfactant on DPPC domain shape in the liquid condensed-liquid ex panded coexistence region showed the opposite result. Neutral surfacta nts had minimal effect on the shape of DPPC domains; charged surfactan ts, on the other hand, induced a new shape transition at high surface pressures previously unreported for DPPC domains. All of these results are discussed with particular attention given to electrostatic effect s at the interface. (C) 1998 Elsevier Science B.V. All rights reserved .