Surfactant Surface Film Research Articles

Lo, and the Niche Is Knit: Lysyl Oxidase Activity and Maintenance of Lung, Aorta, and Skin Integrity

Lo, and the Niche Is Knit: Lysyl Oxidase Activity and Maintenance of Lung, Aorta, and Skin Integrity

Short wave damping in the simultaneous presence of a surface film and turbulence

Spatial decay rates of short gravity waves and gravity‐capillary waves in the frequency range of 3 to 8 Hz were measured in a laboratory wave tank equipped with a submerged oscillating grid to generate turbulence. Experiments were conducted with: clean fresh water, fresh water with an oleyl alcohol insoluble surfactant surface film, fresh water with a Triton X‐100 soluble surfactant surface film, and with sea water having a surface film of its own natural surfactants. With each material, decay rate tests were conducted with and without turbulence. The principal purpose of the study was to determine the extent to which turbulence modified the wave decay due to the presence of surface films. This is of importance for modeling the energy balance of short sea waves which influence microwave backscattering used for remote sensing of the ocean. The results show that the wave decay rate is equal to the sum of the rates due to surfactant alone and with turbulence alone. It is concluded that the statistically stationary component of the turbulence that exists near the free surface does not significantly modify the decay mechanism associated with the presence of the surfactant.

Surface chemistry of binary mixtures of phospholipids in monolayers. Infrared studies of surface composition at varying surface pressures in a pulmonary surfactant model system.

Phospholipid monomolecular films at the air/water interface were studied using Langmuir-Blodgett (L-B) surface chemistry, 31P NMR spectroscopy, and infrared (IR) spectroscopy. These monolayers were composed of binary mixtures of acyl chain perdeuterated 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (i.e., DPPC-d62) with 1,2-dipalmitoyl-sn-glycero-3-phosphoglycerol (i.e., DPPG). This particular PC-PG binary mixture was chosen for study since this lipid system has been used as a model for pulmonary surfactant, especially in conjunction with the so-called "squeezing-out" hypothesis of pulmonary mechanics. This theory predicts that upon successive compression-expansion cycles, a surfactant surface film will reorganize to exclude all components except DPPC, thus resulting in a stable, low surface tension film. Several general results were obtained from these experiments. First, we have developed a combined spectroscopic assay using high-resolution 31P NMR spectroscopy in combination with the C-H and C-D vibrational intensities obtained from the IR spectroscopy of binary mixtures in which one component is acyl chain perdeuterated. Using attenuated total reflectance IR spectroscopy of transferred L-B films, this combined spectroscopic approach allows us to quantitatively describe the fractional composition of each component in the binary monomolecular film. Second, when these methods are applied to transferred monolayer films of DPPC-d62 and DPPG (at an initial PC:PG mole ratio of 7:1), we find no evidence for a "squeezing-out" of the DPPG monolayer component at high surface pressure resulting in an enrichment of the DPPC component in the transferred monolayer film.(ABSTRACT TRUNCATED AT 250 WORDS)

Reversible and irreversible inactivation of preformed pulmonary surfactant surface films by changes in subphase constituents

Several mechanisms for surfactant inactivation have been reported. In this study, we have measured the reversibility of surfactant inactivation caused by various lipid or protein constituents of plasma or by pH changes. A surfactant of bovine origin was studied in a pulsating surfactometer either when surfactants were premixed with different serum constituents (inactivators) or when inactivators were introduced into subphase fluid surrounding surfactant films formed at an air-liquid interface. Subphase exchanges with sodium bicarbonate or sodium borate raised pH and raised minimal surface tensions either when premixed with surfactant or when introduced with saline subphase beneath a preformed surfactant surface film. The pH effects on surfactant film function were reversible for sodium bicarbonate but not for sodium borate when the subphase with bicarbonate or borate was replaced with saline. Lipids (platelet-activating factor or lysophosphatidylcholine) had non-reversible effects on preformed films. Proteins (fibrinogen or C reactive protein) had reversible effects at low concentrations, but reversibility was less evident at high concentrations. Effects with whole serum were non-reversible at low protein concentrations (0.5 mg/ml). These results add evidence that surfactant inactivation can be caused by multiple mechanisms, both reversible and irreversible.

Electrochemical and immunoelectron microscopy evidence of lipid-protein interaction in Langmuir-Blodgett films of the human lung surfactant

The extracellular lung surfactant surface film (ELSSF) which lines the mammalian lung alveoli at the alveolar air-aqueous cell surface interface is vital in both the breathing and the pulmonary defence processes. The molecular composition of, the structure of and the interaction in the ELSSF was studied, after the ELSSF of human lung lavages could be separated from the subphase and reassembled from its components by using the multicompartment Fromherz-type Langmuir-Blodgett trough. Transmission electron microscopy images of immunogold- labelled and negatively stained isolated film specimens were seen in a continuous layer of mostly phospholipid head groups surfactant-specific protein SpA molecules. Electrical double-layer capacitance and oxygen reduction potential measurements carried out by transferring the surface film from the air-water to a mercury-saline interface of a hanging mercury drop electrode revealed a strong lipid-protein SpA interaction. SpA molecules were partly squeezed out from the film by compression; a proteinless lipid film proved to be a condensed multilayer. Contact with SpA transformed the multilayer into a loose monomolecular film. It is suggested that SpA molecules play a lipid-transporting role, removing lipids in excess from the air-water interface into the aqueous subphase and vice versa. Lipid- protein interaction can be of importance in vivo. An explanation of how the surfactant film works during the two phases of breathing is proposed.

On the slow motion of a solid submerged in a fluid with a surfactant surface film

This paper continues the work of Shail and Gooden [1–4] on the motion generated in a semi-infinite fluid by a singularity or submerged solid moving particle when the surface of the fluid is contaminated with a surfactant film. The fluid motion is assumed to be slow and quasi-steady, but the restriction to axially symmetric flows of earlier investigations is removed. The various linearised models of Shail and Gooden [3,4] governing the variation of film concentration are discussed, the constitutive properties of the film being expressed in terms of Boussinesq coefficients of surface shear and dilatational viscosities. The resulting film boundary conditions are applied to solve the non-axially symmetric problem of a Stokeslet placed in the bulk fluid with its axis parallel to the surface (assumed planar throughout the motion), and the results used to calculate approximate expressions for the resistive force on a particle which translates far from and parallel to the surface. A similar analysis is given for the case of a rotelet whose axis is parallel to the surface.

On the slow translation of a solid submerged in a fluid with a surfactant surface film—II

In Shail & Gooden (1982) the problem of a solid particle translating in a semi-infinite fluid, whose surface is contaminated with a surfactant film, was examined in the quasi-steady Stokes flow régime. Various linearised models governing the variation of film concentration were considered, but the analysis was approximate in that the fluid motion generated was represented by that due to a Stokeslet situated at the centre of the particle. In this paper we remove the latter restriction and treat two specific solids, namely a rigid flat circular disk and a sphere, which move axisymmetrically perpendicular to the fluid surface. This surface is assumed to remain plane throughout the motion. The velocity field in the translating-disk problem is represented in terms of harmonic functions, and the resulting mixed boundary-value problems are reduced, for each of the film behaviours examined, to the solution of sets of simultaneous Fredholm integral equations of the second kind. These equations are solved both iteratively and numerically, and the drag on the disk is computed. For the sphere a stream-function formulation in bispherical coordinates is used. Application of the boundary conditions at the sphere and film results in infinite sets of simultaneous linear equations for the coefficients in the eigenfunction expansion of the stream function. These equations are solved by the method of truncation, and the drag on the sphere is determined.

On the slow translation of a solid submerged in a fluid with a surfactant surface film—I

In this paper a class of problems is examined in which a solid particle translates in a semi-infinite fluid whose surface is contaminated with a surfactant film. The fluid motion generated is assumed to be slow, quasi-steady, and axisymmetric. Various linearised models governing the variation of film concentration are encompassed, and the constitutive properties of the film are described in terms of coeficients of surface shear and surface dilatational viscosity. The problem of a Stokeslet whose direction is normal to the film is solved, and the results are applied to computing approximate expressions for the force on a translating particle when far from the surface.

On the flow field induced by an oscillating disk submerged in a semi-infinite viscous fluid with a surfactant surface film

On the basis of the unsteady Stokes' equation the problem of the flow field induced by an oscillating disk fully immersed in a semi-infinite viscous fluid with a surfactant surface layer is solved. The effect of the insoluble surfactant on the hydrodynamics of the oscillating disk is found for varying values of the ratio of the coefficient of the surface shear viscosity to the coefficient of viscosity of the substrate fluid, and depth of the disk below the surface. A new theoretical analysis for obtaining the surface shear viscosity is suggested.