title: Relation between rheological properties and structural changes in monolayers of model lung surfactant under compression.
abstract: rSP-C surfactant monolayers spread on a native physiological model substrate show two plateau regions in the pi/A-isotherm. The first corresponds to the main phase transition in the monolayer from a LE to a LC phase. Its course is non-horizontal because of the complex composition of the lung surfactant. The second plateau, which is much more pronounced, cannot be attributed to a change of the phase state. Brewster angle microscopy images taken in this region show a sharp apparent decrease of the aggregation degree from the LE to the LC state. This process can be considered as a change in the monolayer orientation relative to the direction of the propagated light. Such a change can be the result of monolayer folding and formation of a thicker layer, which is supported by results of rheological measurements. The dilatation elasticity obtained from oscillating barrier and longitudinal wave measurements reveals a pure elastic behaviour with a steep increase in the second plateau region. Because of the insolubility of the pure lipid components, a possible explanation is squeezing protein components of rSP-C or its complexes with lipids out of the monolayer into the bulk.
authors.affiliation: Max-Planck Institut für Kolloid-und Grenzflächenforschung, 14424 Potsdam, Germany. dima@mpikg-golm.mpg.de
authors.forename: D O
authors.initials: DO
authors.lastname: Grigoriev
authors.forename: J
authors.initials: J
authors.lastname: Krägel
authors.forename: A V
authors.initials: AV
authors.lastname: Akentiev
authors.forename: B A
authors.initials: BA
authors.lastname: Noskov
authors.forename: R
authors.initials: R
authors.lastname: Miller
authors.forename: U
authors.initials: U
authors.lastname: Pison
mesh_terms: D015060:1,2-Dipalmitoylphosphatidylcholine / Q000737:chemistry; D008567:Membranes, Artificial; D010169:Palmitic Acids / Q000737:chemistry; D044367:Phase Transition; D010715:Phosphatidylglycerols / Q000737:chemistry; D011312:Pressure; D037721:Pulmonary Surfactant-Associated Protein C / Q000737:chemistry; D011663:Pulmonary Surfactants / Q000737:chemistry*; D011994:Recombinant Proteins / Q000737:chemistry; D012212:Rheology; D013499:Surface Properties
chemical_list: D008567:Membranes, Artificial; D010169:Palmitic Acids; D010715:Phosphatidylglycerols; D037721:Pulmonary Surfactant-Associated Protein C; D011663:Pulmonary Surfactants; D011994:Recombinant Proteins; D015060:1,2-Dipalmitoylphosphatidylcholine