Phase transitions in thin smectic films at the air-water interface

Rapp, Bertram; Gruler, Hans

doi:10.1103/physreva.42.2215

Cited by 80 publications

(75 citation statements)

References 12 publications

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“…Movement of constituents from the interface into the third dimension, regardless of the process by which it occurs, represents a flow, which can define a viscosity (Rapp and Gruler, 1990). At the lowest γ, where the driving force for collapse is greatest, the absence of collapse in the alveolus again demonstrates the high viscosity that defines a solid film.…”

Section: Stability Of the Interfacial Filmmentioning

confidence: 99%

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The biophysical function of pulmonary surfactant

Rugonyi

Biswas

Hall

2008

Respiratory Physiology & Neurobiology

102

153

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Pulmonary surfactant lowers surface tension in the lungs. Physiological studies indicate two key aspects of this function: that the surfactant film forms rapidly; and that when compressed by the shrinking alveolar area during exhalation, the film reduces surface tension to very low values. These observations suggest that surfactant vesicles adsorb quickly, and that during compression, the adsorbed film resists the tendency to collapse from the interface to form a three-dimensional bulk phase. Available evidence suggests that adsorption occurs by way of a rate-limiting structure that bridges the gap between the vesicle and the interface, and that the adsorbed film avoids collapse by undergoing a process of solidification. Current models, although incomplete, suggest mechanisms that would partially explain both rapid adsorption and resistance to collapse as well as how different constituents of pulmonary surfactant might affect its behavior.

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Section: Stability Of the Interfacial Filmmentioning

confidence: 99%

“…The much larger changes in area following compression to γ just below γ e must reflect collapse. The slow collapse rates at low γ, however, also indicates a viscous film (Rapp and Gruler, 1990). Slow relaxation then indicates that at low γ, the viscosity of the fluid film must increase dramatically.…”

Section: Stability Of the Interfacial Filmmentioning

confidence: 99%

The biophysical function of pulmonary surfactant

Rugonyi

Biswas

Hall

2008

Respiratory Physiology & Neurobiology

102

153

View full text Add to dashboard Cite

show abstract

“…The Ͼ e observed in static lungs, therefore, indicate that the alveolar films deviate from equilibrium and must by definition be metastable. The rate at which a film flows into the bulk phase in response to the thermodynamic driving force of ( Ϫ e ) can be used to calculate an effective viscosity (27). The very slow rates at which films in the lungs undergo this process of collapse from the interface indicate that they have achieved the high viscosities that define a solid (2).…”

mentioning

confidence: 99%

The melting of pulmonary surfactant monolayers

Yan¹,

Biswas²,

Laderas

et al. 2007

Journal of Applied Physiology

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Yan W, Biswas SC, Laderas TG, Hall SB. The melting of pulmonary surfactant monolayers. J Appl Physiol 102: 1739 -1745, 2007. First published December 28, 2006; doi:10.1152/japplphysiol.00948.2006.-Monomolecular films of phospholipids in the liquid-expanded (LE) phase after supercompression to high surface pressures (), well above the equilibrium surface pressure ( e) at which fluid films collapse from the interface to form a three-dimensional bulk phase, and in the tiltedcondensed (TC) phase both replicate the resistance to collapse that is characteristic of alveolar films in the lungs. To provide the basis for determining which film is present in the alveolus, we measured the melting characteristics of monolayers containing TC dipalmitoyl phosphatidylcholine (DPPC), as well as supercompressed 1-palmitoyl-2-oleoyl phosphatidylcholine and calf lung surfactant extract (CLSE). Films generated by appropriate manipulations on a captive bubble were heated from Յ27°C to Ն60°C at different constant above e. DPPC showed the abrupt expansion expected for the TC-LE phase transition, followed by the contraction produced by collapse. Supercompressed CLSE showed no evidence of the TC-LE expansion, arguing that supercompression did not simply convert the mixed lipid film to TC DPPC. For both DPPC and CLSE, the melting point, taken as the temperature at which collapse began, increased at higher , in contrast to 1-palmitoyl-2-oleoyl phosphatidylcholine, for which higher produced collapse at lower temperatures. For between 50 and 65 mN/m, DPPC melted at 48 -55°C, well above the main transition for bilayers at 41°C. At each , CLSE melted at temperatures Ͼ10°C lower. The distinct melting points for TC DPPC and supercompressed CLSE provide the basis by which the nature of the alveolar film might be determined from the temperature-dependence of pulmonary mechanics. captive bubble; dipalmitoyl phosphatidylcholine; jammed; monolayer; pulmonary mechanics; supercompressed THE BEHAVIOR OF PULMONARY surfactant indicates that films at the air/water interface in the alveoli are solid. Multiple approaches consistently indicate that, when compressed by the decreasing alveolar surface area during exhalation, the films of pulmonary surfactant reach high surface pressures () (13,19,30,35,37,39). The observed values are well above the equilibrium spreading pressure ( e ) of ϳ46 mN/m, at which two-dimensional monomolecular films coexist at equilibrium with their three-dimensional bulk phases (14). Films under equilibrium conditions never reach Ͼ e , because compression produces only flow of constituents into the bulk phase, with no increase in the density of material within the interface. The Ͼ e observed in static lungs, therefore, indicate that the alveolar films deviate from equilibrium and must by definition be metastable. The rate at which a film flows into the bulk phase in response to the thermodynamic driving force of ( Ϫ e ) can be used to calculate an effective viscosity (27). The very slow rates at which films in the lungs undergo this p...

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“…Investigated topics are, for example, novel colloidal interactions between isotropic droplets in a nematic matrix [1,2], pressure-induced layering transitions in smectic Langmuir films [3][4][5], electro-optic properties of nematic emulsions [6,7], defect structures in nematic droplets and shells [8][9][10][11], the anchoring behavior of LCs at surfactant-laden LC-water interfaces [12][13][14][15], or the assembly of biomolecules, polymers, and similar species at nematic LC-water interfaces [16][17][18][19][20].…”

Section: Introductionmentioning

confidence: 99%

Surface order at surfactant-laden interfaces between isotropic liquid crystals and liquid phases with different polarity

Feng

Bahr

2011

Phys. Rev. E

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We present an ellipsometry study of the interface between thermotropic liquid crystals and liquid phases consisting of various binary mixtures of water and glycerol. The liquid-crystal samples contain a small constant amount of a surfactant which induces a homeotropic anchoring at the interface. We determine the smectic or nematic order at the interface in the temperature range above the liquid-crystal-isotropic transition while the water to glycerol ratio is varied, corresponding to a systematic modification of the polarity of the liquid phase. The surface-induced order becomes less pronounced with increasing glycerol concentration in the liquid phase. The observed behavior is compared with previous studies in which the surfactant concentration in the liquid-crystal bulk phase was varied. The results indicate that in both cases the magnitude of the surfactant coverage at the interface is the key quantity which determines the liquid-crystal surface order at the interface.

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Phase transitions in thin smectic films at the air-water interface

Cited by 80 publications

References 12 publications

The biophysical function of pulmonary surfactant

The biophysical function of pulmonary surfactant

The melting of pulmonary surfactant monolayers

Surface order at surfactant-laden interfaces between isotropic liquid crystals and liquid phases with different polarity

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