In the current work we study with monolayer tensiometry and Brewster angle microscopy (BAM) the surface properties of Dipalmitoleoylphosphatidylethanolamine (DPoPE) films at the air/water interface in presence and absence of specific surfactant protein C (SP-C). DPoPE is used, as it readily forms both lamellar (L(alpha)) and non-lamellar inverted hexagonal (H(II)) phases and appears as a suitable model phospholipid for probing the interfacial properties of distinct lipid phases. At pure air/water interface L(alpha) shows faster adsorption and better surface disintegration than H(II) phase. The interaction of DPoPE molecules with SP-C (predeposited at the interface) results in equalizing of the interfacial disintegration of the both phases (reaching approximately the same equilibrium surface tension) although the adsorption kinetics of the lamellar phase remains much faster. Monolayer compression/decompression cycling revealed that the effect of SP-C on dynamic surface tensions (gamma (max) and gamma (min)) of mixed films is remarkably different for the two phases. If gamma (max) for L(alpha) decreased from the first to the third cycle, the opposite effect is registered for H(II) where gamma (max) increases during cycling. Also the significant decrease of gamma (min) for L(alpha) in SP-C presence is not observed for H(II) phase. BAM studies reveal the formation of more uniform and homogeneously packed DPoPE monolayers in the presence of SP-C.

The aim of the study is to examine the influence of the lysophosphatidylcholine (lysoPC) to surface properties of INFASURF, a replacement lung surfactant, using the methods of thin foam films and Wilhelmy method. By the latter it is shown the change of surface tension (γ, mN/m) during time of the pure INFASURF and their mixture with lysoPC. Foam films are an efficient and useful model for the study of many surface phenomena especially for investigating the surface properties of pulmonary surfactant. Formation and stability of common black foam films (CBF) of pure INFASURF and of mixtures with various concentrations of lysoPC indicate the influence of low concentrations of lysoPC for the stability of CBF from INFASURF. It is proved that the curve W/C (where W is probability and C -concentration) is shifted to the lower concentrations.

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