An analysis of the interaction of protein with lipid monolayers at the air/water interface

1. Measurements have been made of the interaction of cytochrome c, bovine serum albumin and synthetic oxytocin with low-pressure (2dyn/cm) monolayers of stearic acid, phosphatidylcholine and phosphatidylethanolamine. 2. [14C]Carboxymethylation of the cytochrome c and albumin followed by surface-radioactivity determinations have shown that only a proportion of the protein added to the subphase is bound to the monolayers and that initially the degree of binding is dependent on the protein concentration. The binding is irreversible in the sense that the adsorbed protein cannot be removed by transferring the film containing the interacted protein to a fresh subphase containing no protein. 3. Three successive types of interaction can usually be recognized. (a) Initially, whole molecules of protein penetrate the lipid film and occupy the same area as those of the protein spread at the air/water interface. (b) Above certain film pressures a part of each protein molecule, probably hydrophobic side chains, penetrates the film. The change in surface pressure per unit of bound protein is much smaller than in (a). (c) At higher film pressures, adsorption without penetration occurs. With cytochrome c this is initially dependent on a favourable electrostatic interaction.

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Absorption of Bovine Serum Albumin at Air-Water Interface and Penetration into Lipid Monolayers

YAKUGAKU ZASSHI ◽

10.1248/yakushi1947.99.10_999 ◽

1979 ◽

Vol 99 (10) ◽

pp. 999-1006 ◽

Cited By ~ 3

Author(s):

MASAYUKI NAKAGAKI ◽

HITOSHI ICHIHASHI

Keyword(s):

Bovine Serum Albumin ◽

Serum Albumin ◽

Bovine Serum ◽

Lipid Monolayers ◽

Water Interface ◽

Air Water Interface

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Nanoparticle interaction with model lung surfactant monolayers

Journal of The Royal Society Interface ◽

10.1098/rsif.2009.0329.focus ◽

2009 ◽

Vol 7 (suppl_1) ◽

Cited By ~ 83

Author(s):

Rakesh Kumar Harishchandra ◽

Mohammed Saleem ◽

Hans-Joachim Galla

Keyword(s):

Surface Properties ◽

Self Assembly ◽

Current Knowledge ◽

Surface Film ◽

Lung Surfactant ◽

Hydrophobic Surface ◽

Surface Pattern ◽

Lipid Monolayers ◽

Water Interface ◽

Air Water Interface

One of the most important functions of the lung surfactant monolayer is to form the first line of defence against inhaled aerosols such as nanoparticles (NPs), which remains largely unexplored. We report here, for the first time, the interaction of polyorganosiloxane NPs (AmorSil20: 22 nm in diameter) with lipid monolayers characteristic of alveolar surfactant. To enable a better understanding, the current knowledge about an established model surface film that mimics the surface properties of the lung is reviewed and major results originating from our group are summarized. The pure lipid components dipalmitoylphosphatidylcholine and dipalmitoylphosphatidylglycerol have been used to study the biophysical behaviour of their monolayer films spread at the air–water interface in the presence of NPs. Film balance measurements combined with video-enhanced fluorescence microscopy have been used to investigate the formation of domain structures and the changes in the surface pattern induced by NPs. We are able to show that NPs are incorporated into lipid monolayers with a clear preference for defect structures at the fluid–crystalline interface leading to a considerable monolayer expansion and fluidization. NPs remain at the air–water interface probably by coating themselves with lipids in a self-assembly process, thereby exhibiting hydrophobic surface properties. We also show that the domain structure in lipid layers containing surfactant protein C, which is potentially responsible for the proper functioning of surfactant material, is considerably affected by NPs.

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