Fig. 4.

Glycerophospholipid headgroups do not alter PEG-induced isotherm variations. DPPC, DPPE and DPPS were applied on Milli-Q water subphase and monolayer compression was performed at 37°C without (zero reference) or with 30 g/L of PEG of different molecular weights (ethylene glycol (EG), PEG 400 Da, PEG 4,000 Da, PEG 10,000 Da, PEG 20,000 Da, PEG 35,000 Da). Surface pressure/mean molecular area isotherms were obtained as described in the “Materials and methods” section. Relative modification from pure Milli-Q water subphase was expressed as the percentage of variation in mean molecular area (mma) measured at the lift-off point (a) or at 30 mN/m (b) or as the percentage of variation in surface pressure (Π) measured at the collapse-point (c). Results are means ± SD of two independent experiments