Fig. 6.

Ionic strength and pH solution modifications increase PEG-induced isotherm variations at low surface area and decrease PEG-induced isotherm variations at the collapse-point on DPPC monolayer. DPPC was applied on Milli-Q water subphase or on EC solution subphase and monolayer compression was performed at 37°C without (zero reference) or with 1 g/L of PEG 20,000 Da or 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. *p < 0.05, **p < 0.001, EC solution subphase versus pure Milli-Q water subphase or PEG 20,000 Da versus PEG 35,000 Da