The Accelerated Late Adsorption of Pulmonary Surfactant

Loney, Ryan W.; Rananavare, Shankar B.; Hall, Stephen B.

doi:10.1016/j.bpj.2010.12.3642

Cited by 3 publications

(6 citation statements)

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“…The proteins greatly accelerate the adsorption of the lipids, which by themselves adsorb slowly and incompletely. 17 The surface tension at end-adsorption provided the lower boundary of the coexistence region. With progressive increases in surface concentration, produced either by added constituents or decreasing area, conversion of the monolayer to the bulk phase continues until the three-dimensional structure exists in excess.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

The Equilibrium Spreading Tension of Pulmonary Surfactant

Dagan

Hall

2015

Langmuir

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Monomolecular films at an air/water interface coexist at the equilibrium spreading tension (γe) with the bulk phase from which they form. For individual phospholipids, γe is single-valued, and separates conditions at which hydrated vesicles adsorb from tensions at which overcompressed monolayers collapse. With pulmonary surfactant, isotherms show that monolayers compressed on the surface of bubbles coexist with the three-dimensional collapsed phase over a range of surface tensions. γe therefore represents a range rather than a single value of surface tension. Between the upper and lower ends of this range, rates of collapse for spread and adsorbed films decrease substantially. Changes during adsorption across this narrow region of coexistence between the two- and three-dimensional structures at least partially explain how alveolar films of pulmonary surfactant become resistant to collapse.

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Section: ■ Results and Discussionmentioning

confidence: 99%

The Equilibrium Spreading Tension of Pulmonary Surfactant

Dagan

Hall

2015

Langmuir

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“…Phosphatidylethanolamines (PEs) and gramicidin-A induce lipid leaflets to adopt curvature that is negative, with a concave hydrophilic face. These compounds promote faster adsorption (7)(8)(9)(10). Lysophosphatidylcholine, which contributes to positive curvature of a leaflet (11), inhibits adsorption (12).…”

Section: Introductionmentioning

confidence: 99%

“…The hydrophobic surfactant proteins (SPs), SP-B and SP-C, greatly accelerate adsorption of the surfactant lipids (10,13). The relationship between curvature and kinetics established for exogenous modulators suggests that the proteins may achieve their effect by promoting the formation of a negatively curved, rate-limiting structure.…”

Section: Introductionmentioning

confidence: 99%

An Anionic Phospholipid Enables the Hydrophobic Surfactant Proteins to Alter Spontaneous Curvature

Chavarha

Loney

Rananavare

et al. 2013

Biophysical Journal

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The hydrophobic surfactant proteins, SP-B and SP-C, greatly accelerate the adsorption of the surfactant lipids to an air/water interface. Previous studies of factors that affect curvature suggest that vesicles may adsorb via a rate-limiting structure with prominent negative curvature, in which the hydrophilic face of the lipid leaflets is concave. To determine if SP-B and SP-C might promote adsorption by inducing negative curvature, we used small-angle x-ray scattering to test whether the physiological mixture of the two proteins affects the radius of cylindrical monolayers in the inverse hexagonal phase. With dioleoyl phosphatidylethanolamine alone, the proteins had no effect on the hexagonal lattice constant, suggesting that the proteins fail to insert into the cylindrical monolayers. The surfactant lipids also contain ∼10% anionic phospholipids, which might allow incorporation of the cationic proteins. With 10% of the anionic dioleoyl phosphatidylglycerol added to dioleoyl phosphatidylethanolamine, the proteins induced a dose-related decrease in the hexagonal lattice constant. At 30°C, the reduction reached a maximum of 8% relative to the lipids alone at ∼1% (w/w) protein. Variation of NaCl concentration tested whether the effect of the protein represented a strictly electrostatic effect that screening by electrolyte would eliminate. With concentrations up to 3 M NaCl, the dose-related change in the hexagonal lattice constant decreased but persisted. Measurements at different hydrations determined the location of the pivotal plane and proved that the change in the lattice constant produced by the proteins resulted from a shift in spontaneous curvature. These results provide the most direct evidence yet that the surfactant proteins can induce negative curvature in lipid leaflets. This finding supports the model in which the proteins promote adsorption by facilitating the formation of a negatively curved, rate-limiting structure.

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“…Studies in vitro show that the hydrophobic surfactant proteins (SPs), SP–B and SP–C, greatly increase the rate at which the surfactant lipids adsorb. With a clean interface, devoid of a film, the high surface tension can drive adsorption of vesicles containing only lipids . Approaching the equilibrium spreading tension, adsorption requires the proteins …”

Section: Introductionmentioning

confidence: 99%

“…With a clean interface, devoid of a film, the high surface tension can drive adsorption of vesicles containing only lipids. 4 Approaching the equilibrium spreading tension, adsorption requires the proteins. 4 Any model of how the proteins promote adsorption must explain a fundamental observation.…”

Section: ■ Introductionmentioning

confidence: 99%

Differential Effects of the Hydrophobic Surfactant Proteins on the Formation of Inverse Bicontinuous Cubic Phases

et al. 2012

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Prior studies have shown that the biological mixture of the two hydrophobic surfactant proteins, SP–B and SP–C, produces faster adsorption of the surfactant lipids to an air/water interface, and that they induce 1-palmitoyl-2-oleoyl phosphatidylethanolamine (POPE) to form inverse bicontinuous cubic phases. Previous studies have shown that SP–B has a much greater effect than SP–C on adsorption. If the two proteins induce faster adsorption and formation of the bicontinuous structures by similar mechanisms, then they should also have different abilities to form the cubic phases. To test this hypothesis, we measured small angle X-ray scattering on the individual proteins combined with POPE. SP–B replicated the dose-related ability of the combined proteins to induce the cubic phases at temperatures more than 25°C below the point at which POPE alone forms the curved inverse-hexagonal phase. With SP–C, diffraction from cubic structures was either absent or present at very low intensities only with larger amounts of protein. The correlation between the structural effects of inducing curved structures and the functional effects on the rate of adsorption fits with the model in which SP–B promotes adsorption by facilitating formation of an inversely curved, rate-limiting structure.

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The Accelerated Late Adsorption of Pulmonary Surfactant

Cited by 3 publications

References 0 publications

The Equilibrium Spreading Tension of Pulmonary Surfactant

The Equilibrium Spreading Tension of Pulmonary Surfactant

An Anionic Phospholipid Enables the Hydrophobic Surfactant Proteins to Alter Spontaneous Curvature

Differential Effects of the Hydrophobic Surfactant Proteins on the Formation of Inverse Bicontinuous Cubic Phases

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