Biophysical characterization and modeling of lung surfactant components

The present study characterizes the dynamic interfacial properties of calf lung surfactant (CLS) and samples reconstituted in a stepwise fashion from phospholipid (PL), hydrophobic apoprotein (HA), surfactant apoprotein A (SP-A), and neutral lipid fractions. Dipalmitoylphosphatidylcholine (DPPC), the major PL component of surfactant, was examined for comparison. Surface tension was measured over a range of oscillation frequencies (1–100 cycles/min) and bulk phase concentrations (0.01–1 mg/ml) by using a pulsating bubble surfactometer. Distinct differences in behavior were seen between samples. These differences were interpreted by using a previously validated model of surfactant adsorption kinetics that describes function in terms of 1) adsorption rate coefficient ( k 1), 2) desorption rate coefficient ( k 2), 3) minimum equilibrium surface tension (γ*), 4) minimum surface tension at film collapse (γmin), and 5) change in surface tension with interfacial area for γ < γ* ( m 2). Results show that DPPC and PL have k 1 and k 2 values several orders of magnitude lower than CLS. PL had a γmin of 19–20 dyn/cm, significantly greater than CLS (nearly zero). Addition of the HA to PL restored dynamic interfacial behavior to nearly that of CLS. However, m 2 remained at a reduced level. Addition of the SP-A to PL + HA restored m 2 to a level similar to that of CLS. No further improvement in function occurred with the addition of the neutral lipid. These results support prior studies that show addition of HA to the PL markedly increases adsorption and film stability. However, SP-A is required to completely normalize dynamic behavior.

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Effects of fixatives on function of pulmonary surfactant

Journal of Applied Physiology ◽

10.1152/japplphysiol.00227.2002 ◽

2002 ◽

Vol 93 (3) ◽

pp. 911-916 ◽

Cited By ~ 9

Author(s):

H. Bachofen ◽

U. Gerber ◽

S. Schürch

Keyword(s):

Surface Tension ◽

Pulmonary Surfactant ◽

Osmium Tetroxide ◽

Uranyl Acetate ◽

Film Stability ◽

Minimum Surface ◽

Natural Surfactant ◽

Equilibrium Surface Tension ◽

Minimum Surface Tension ◽

Surface Active

The structure of pulmonary surfactant films remains ill defined. Although plausible film fragments have been imaged by electron microscopy, questions about the significance of the findings and even about the true fixability of surfactant films by the usual fixatives glutaraldehyde (GA), osmium tetroxide (OsO4), and uranyl acetate (UA) have not been settled. We exposed functioning natural surfactant films to fixatives within a captive bubble surfactometer and analyzed the effect of fixatives on surfactant function. The capacity of surfactant to reach near-zero minimum surface tension on film compression was barely impaired after exposure to GA or OsO4. Although neither GA nor OsO4 prevented the surfactant from forming a surface active film, GA increased the equilibrium surface tension to above 30 mN/m, and both GA and OsO4 decreased film stability as seen in the slowly rising minimum surface tension from 1 to ∼5 mN/m in 10 min. In contrast, the effect of UA seriously impaired surface activity in that both adsorption and minimum surface tension were substantially increased. In conclusion, the fixatives tested in this study are not suitable to fix, i.e., to solidify, surfactant films. Evidently, however, OsO4 and UA may serve as staining agents.

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Alterations in the surface properties of lung surfactant in the torpid marsupial Sminthopsis crassicaudata

Journal of Applied Physiology ◽

10.1152/jappl.1998.84.1.146 ◽

1998 ◽

Vol 84 (1) ◽

pp. 146-156 ◽

Cited By ~ 21

Author(s):

Olga V. Lopatko ◽

Sandra Orgeig ◽

Christopher B. Daniels ◽

David Palmer

Keyword(s):

Surface Tension ◽

Surface Properties ◽

Surface Activity ◽

Pulmonary Surfactant ◽

Lung Surfactant ◽

Lung Compliance ◽

Equilibrium Surface Tension ◽

Sminthopsis Crassicaudata

Lopatko, Olga V., Sandra Orgeig, Christopher B. Daniels, and David Palmer. Alterations in the surface properties of lung surfactant in the torpid marsupial Sminthopsis crassicaudata. J. Appl. Physiol. 84(1): 146–156, 1998.—Torpor changes the composition of pulmonary surfactant (PS) in the dunnart Sminthopsis crassicaudata [C. Langman, S. Orgeig, and C. B. Daniels. Am. J. Physiol. 271 ( Regulatory Integrative Comp. Physiol. 40): R437–R445, 1996]. Here we investigated the surface activity of PS in vitro. Five micrograms of phospholipid per centimeter squared surface area of whole lavage (from mice or from warm-active, 4-, or 8-h torpid dunnarts) were applied dropwise onto the subphase of a Wilhelmy-Langmuir balance at 20°C and stabilized for 20 min. After 4 h of torpor, the adsorption rate increased, and equilibrium surface tension (STeq), minimal surface tension (STmin), and the %area compression required to achieve STmin decreased, compared with the warm-active group. After 8 h of torpor, STmin decreased [from 5.2 ± 0.3 to 4.1 ± 0.3 (SE) mN/m]; %area compression required to achieve STmindecreased (from 43.4 ± 1.0 to 27.4 ± 0.8); the rate of adsorption decreased; and STeqincreased (from 26.3 ± 0.5 to 38.6 ± 1.3 mN/m). ST-area isotherms of warm-active dunnarts and mice at 20°C had a shoulder on compression and a plateau on expansion. These disappeared on the isotherms of torpid dunnarts. Samples of whole lavage (from warm-active and 8-h torpor groups) containing 100 μg phospholipid/ml were studied by using a captive-bubble surfactometer at 37°C. After 8 h of torpor, STmin increased (from 6.4 ± 0.3 to 9.1 ± 0.3 mN/m) and %area compression decreased in the 2nd (from 88.6 ± 1.7 to 82.1 ± 2.0) and 3rd (from 89.1 ± 0.8 to 84.9 ± 1.8) compression-expansion cycles, compared with warm-active dunnarts. ST-area isotherms of warm-active dunnarts at 37°C did not have a shoulder on compression. This shoulder appeared on the isotherms of torpid dunnarts. In conclusion, there is a strong correlation between in vitro changes in surface activity and in vivo changes in lipid composition of PS during torpor, although static lung compliance remained unchanged (see Langman et al. cited above). Surfactant from torpid animals is more active at 20°C and less active at 37°C than that of warm-active animals, which may represent a respiratory adaptation to low body temperatures of torpid dunnarts.

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Evaluation of pressure-driven captive bubble surfactometer

Journal of Applied Physiology ◽

10.1152/jappl.1994.76.4.1417 ◽

1994 ◽

Vol 76 (4) ◽

pp. 1417-1424 ◽

Cited By ~ 50

Author(s):

G. Putz ◽

J. Goerke ◽

S. Schurch ◽

J. A. Clements

Keyword(s):

Surface Tension ◽

Surface Properties ◽

Lung Surfactant ◽

Surface Adsorption ◽

Accurate Information ◽

Equilibrium Surface Tension ◽

Adsorption Rates ◽

Surface Balance ◽

Good Agreement ◽

Made In

We modified the captive bubble surfactometer [S. Schurch et al. J. Appl. Physiol. 67: 2389–2396, 1989] to facilitate the measurement of surface adsorption rates and to simplify its construction. We used a range of standards and monolayers of dipalmitoylphosphatidylcholine to check the calibration of the device against measurements made in a Wilhelmy surface balance and in the captive bubble by using a cathetometer, and we found good agreement. As a further test we measured the surface properties of rabbit lavage lung surfactant (60,000 x average g for 60 min) at 1.0 mg phospholipid/ml. This material adsorbed within 1 s to near-equilibrium surface tension, reached surface tensions of < 5 mN/m on the second compression, and formed very stable films. We conclude that a captive bubble surfactometer can provide accurate information about important surface properties of lung surfactant films.

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Mechanisms of peroxynitrite-induced injury to pulmonary surfactants

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.1993.265.6.l555 ◽

1993 ◽

Vol 265 (6) ◽

pp. L555-L564 ◽

Cited By ~ 28

Author(s):

I. Y. Haddad ◽

H. Ischiropoulos ◽

B. A. Holm ◽

J. S. Beckman ◽

J. R. Baker ◽

...

Keyword(s):

Surface Tension ◽

Dynamic Compression ◽

Lung Surfactant ◽

Thiobarbituric Acid ◽

Surfactant Protein ◽

Surfactant Proteins ◽

Minimum Surface ◽

Surfactant Protein B ◽

Minimum Surface Tension ◽

By Products

Activated alveolar macrophages secrete both nitric oxide and superoxide in the alveolar lining fluid which combine rapidly to form peroxynitrite, a potent oxidizing agent capable of damaging lipids and proteins in biological membranes. Peroxynitrite (1 mM) plus 100 microM Fe3+EDTA inhibited calf lung surfactant extract (CLSE) from reaching a minimum surface tension below 10 mN/m on dynamic compression. Peroxynitrite and its by-products reacted with the unsaturated lipid components of CLSE, as evidenced by the appearance of conjugated dienes and thiobarbituric acid products, and damaged all surfactant proteins. A mixture of the hydrophobic proteins [surfactant protein B (SP-B) and surfactant protein C (SP-C)] exposed to peroxynitrite became incapable of lowering phospholipid minimum surface tension on dynamic compression. Exposure of SP-A to peroxynitrite decreased its ability to cause lipid aggregation and to act synergistically with SP-B and SP-C in lowering surface tension of surfactant lipids. Western blot analysis of SP-A exposed to peroxynitrite was consistent with fragmentation and polymerization of the 28- to 36-kDa triplet band, and amino acid analysis revealed the presence of significant levels of 3-nitro-L-tyrosine. We conclude that peroxynitrite and its reactive intermediates inhibit pulmonary surfactant function by lipid peroxidation and damaging surfactant proteins.

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Dependence of surfactant function on extracellular pH: mechanisms and modifications

Journal of Applied Physiology ◽

10.1152/jappl.1994.76.2.657 ◽

1994 ◽

Vol 76 (2) ◽

pp. 657-662 ◽

Cited By ~ 12

Author(s):

I. Y. Haddad ◽

B. A. Holm ◽

L. Hlavaty ◽

S. Matalon

Keyword(s):

Surface Tension ◽

Ph Value ◽

Dynamic Compression ◽

Lung Surfactant ◽

Protein A ◽

Lung Mechanics ◽

Normal Lung ◽

Surfactant Mixtures ◽

Minimum Surface ◽

Minimum Surface Tension

We investigated alterations in pH on the surface properties of natural lung surfactant and the calf lung surfactant extract (CLSE), suspended in 10 mM N-2-hydroxyethylpiperazine-N′-2-ethanesulfonic acid, using a pulsating bubble surfactometer. Increasing the pH value of the medium to > 7.4 decreased the ability of CLSE, but not of natural lung surfactant mixtures (2 mg phospholipid/ml), to achieve a low minimum surface tension during dynamic compression and enhanced their sensitivity to albumin inactivation. These detrimental effects on surface tension were reversed by addition of surfactant protein A (SP-A; 3% by weight) or by increasing the lipid concentration to 4 mg/ml. SP-A-induced lipid aggregation at pH 10 was not different than at pH 7.4. Alkalinization impaired the ability of CLSE to restore normal lung mechanics in excised surfactant-deficient rats lungs. These results indicate that cooperation between SP-A and the hydrophobic surfactant proteins has an important role in achieving low minimum surface tension at pH > or = 7.6.

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A pH-Responsive Foam Formulated with PAA/Gemini 12-2-12 Complexes

Colloids and Interfaces ◽

10.3390/colloids5030037 ◽

2021 ◽

Vol 5 (3) ◽

pp. 37

Author(s):

Hernán Martinelli ◽

Claudia Domínguez ◽

Marcos Fernández Leyes ◽

Sergio Moya ◽

Hernán Ritacco

Keyword(s):

Surface Tension ◽

Dynamic Surface Tension ◽

Foam Formation ◽

Ph Responsive ◽

Dynamic Surface ◽

X Ray ◽

Equilibrium Surface Tension ◽

Potential Applications ◽

The Stability ◽

Air Interfaces

In the search for responsive complexes with potential applications in the formulation of smart dispersed systems such as foams, we hypothesized that a pH-responsive system could be formulated with polyacrylic acid (PAA) mixed with a cationic surfactant, Gemini 12-2-12 (G12). We studied PAA-G12 complexes at liquid–air interfaces by equilibrium and dynamic surface tension, surface rheology, and X-ray reflectometry (XRR). We found that complexes adsorb at the interfaces synergistically, lowering the equilibrium surface tension at surfactant concentrations well below the critical micelle concentration (cmc) of the surfactant. We studied the stability of foams formulated with the complexes as a function of pH. The foams respond reversibly to pH changes: at pH 3.5, they are very stable; at pH > 6, the complexes do not form foams at all. The data presented here demonstrate that foam formation and its pH responsiveness are due to interfacial dynamics.

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