Design and construction of an epifluorescence microscopic surface balance for the study of lipid monolayer phase transitions

Nag, Kaushik; Boland, Carl; Rich, Nathan H.; Keough, K. M. W.

doi:10.1063/1.1141596

Cited by 37 publications

(41 citation statements)

References 11 publications

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“…1 a) occurred due to increased packing density of the lipids and is equivalent to the increase in ir seen during compression of solvent-spread monolayers. The LC domains of DPPC in solvent-spread monolayers that have been compressed relatively slowly display a kidney bean shape (Florsheimer and Mohwald, 1989;McConnell, 1991;Nag et al, 1990;Weis and Mc-Connell, 1985), and these are seen at similar 7r in the adsorbed monolayers ( Fig. 1 b, B).…”

Section: Resultsmentioning

confidence: 83%

“…Adsorption was observed on a modified version of an epifluorescent microscopic surface balance (Nag et al, 1990). The original surface balance consisted of a custom-designed Langmuir trough with epifluorescence microscopic attachments.…”

Section: Epifluorescence Microscopic Adsorption Apparatusmentioning

confidence: 99%

“…Vesicular suspensions of DPPC or DPPC plus protein were injected under the air-buffer interface of the surface balance discussed above. The change of surface pressure (jr) during adsorption from vesicles was monitored by a roughened platinum Wilhelmy dipping plate attached to a pressure transducer connected to a personal computer, as discussed in detail elsewhere (Nag et al, 1990(Nag et al, , 1991. Experiments were performed at a temperature of 22 ± 2°C.…”

Section: Monolayer Formation and Visual Observationmentioning

confidence: 99%

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Spontaneous formation of interfacial lipid-protein monolayers during adsorption from vesicles

Nag¹,

Pérez‐Gil²,

Cruz³

et al. 1996

Biophysical Journal

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Spread and adsorbed monolayers of lipid-protein mixtures have served as models for biomembranes and pulmonary surfactant, but their similarity was unclear. Epifluorescence microscopy of monolayers spontaneously adsorbed from vesicles of dipalmitoylphosphatidylcholine or dipalmitoylphosphatidylcholine plus surfactant protein C (SP-C) showed gas, liquid expanded, and liquid condensed (LC) domains. The shapes and distribution of LC domains in the adsorbed and solvent-spread monolayers were quite similar. Labeled SP-C adsorbed into the air-water interface in the company of the lipids. In both forms of monolayers, SP-C occupied the fluid phase and reduced the size and amount of the LC domains. The properties suggest that these adsorbed and spread monolayers are analogous to one another.

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Section: Resultsmentioning

confidence: 83%

Section: Epifluorescence Microscopic Adsorption Apparatusmentioning

confidence: 99%

Section: Monolayer Formation and Visual Observationmentioning

confidence: 99%

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Spontaneous formation of interfacial lipid-protein monolayers during adsorption from vesicles

Nag¹,

Pérez‐Gil²,

Cruz³

et al. 1996

Biophysical Journal

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“…The BLES in chloroform:methanol (3:1) containing 1 mol % (total BLES phospholipids by weight) of NBD-PC was spread on the air-water interface of a epifluorescence microscopic surface balance (Kibron Scientific, Helsinki, Finland). Details of design and performance of a similar surface balance has been discussed elsewhere (Nag et al, 1990). All studies were performed on the surface balance at an ambient room temperature (23°C Ϯ 1°C).…”

Section: Film Preparation and Imagingmentioning

confidence: 99%

Segregation of Saturated Chain Lipids in Pulmonary Surfactant Filmsand Bilayers

Nag

Pao

Harbottle

et al. 2002

Biophysical Journal

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The physical properties of organized system (bilayers and monolayers at the air water interface) composed of bovine lipid extract surfactant (BLES) were studied using correlated experimental techniques. 6-Dodecanoyl-2-dimethylamino-naphthalene (LAURDAN)-labeled giant unilamelar vesicles (mean diameter approximately 30 microm) composed of BLES were observed at different temperatures using two-photon fluorescence microscopy. As the temperature was decreased, dark domains (gel-like) appeared at physiological temperature (37 degrees C) on the surface of BLES giant unilamelar vesicles. The LAURDAN two-photon fluorescent images show that the gel-like domains span the lipid bilayer. Quantitative analysis of the LAURDAN generalized polarization function suggests the presence of a gel/fluid phase coexistence between 37 degrees C to 20 degrees C with low compositional and energetic differences between the coexisting phases. Interestingly, the microscopic scenario of the phase coexistence observed below 20 degrees C shows different domain's shape compared with that observed between 37 degrees C to 20 degrees C, suggesting the coexistence of two ordered but differently organized lipid phases on the bilayer. Epifluorescence microscopy studies of BLES monomolecular films doped with small amounts of fluorescent lipids showed the appearance and growth of dark domains (liquid condensed) dispersed in a fluorescent phase (liquid expanded) with shapes and sizes similar to those observed in BLES giant unilamelar vesicles. Our study suggests that bovine surfactant lipids can organize into discrete phases in monolayers or bilayers with equivalent temperature dependencies and may occur at physiological temperatures and surface pressures equivalent to those at the lung interface.

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“…Solvent-spread or vesicle-spread monolayers were tested on an epi¯uorescence surface balance (Nag et al 1990). The trough of the balance had a total surface of 160 cm 2 and all experiments were performed at a temperature of 21 1°C.…”

Section: P-a and Monolayer Relaxation Measurementsmentioning

confidence: 99%

Microstructure and dynamic surface properties of surfactant protein SP-B/dipalmitoylphosphatidylcholine interfacial films spread from lipid-protein bilayers

Cruz¹,

Worthman

Serrano³

et al. 2000

Eur Biophys J

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Suspensions of dipalmitoylphosphatidylcholine (DPPC) bilayers containing 5, 10 or 20% (w/w) surfactant protein SP-B have been reconstituted and spread at air-liquid interfaces. Compression isotherms of DPPC/SP-B monolayers spread from these preparations were qualitatively comparable to the isotherms of the corresponding DPPC/SP-B monolayers spread from solvents. SP-B was squeezed-out at higher pressures from vesicle-spread films than from solvent-spread monolayers. SP-B caused a marked decrease on the rate of relaxation of DPPC collapse phases to equilibrium pressures in all the lipid/protein films assayed. This stabilizing effect was higher in vesicle-spread than in solvent-spread monolayers. Inclusion in the films of traces of the fluorescent probe NBD-PC (1 mol%) and use of a fluorescent derivative of SP-B labeled with a rhodamine derivative, Texas Red, allowed for direct observation of protein and lipid domains at the interface by epifluorescence microscopy. Upon compression, SP-B altered the packing of phospholipids in the bilayer-spread films, observed as a SP-B-induced reduction of the area of liquid-condensed domains, in a way similar to its effect in solvent-spread monolayers. SP-B was not associated with condensed regions of the films. Fluorescence images from vesicle-spread films showed discrete fluorescent aggregates that could be consistent with the existence of lipid-protein vesicles in close association with the monolayer. Both the retention of SP-B at higher surface pressures and the greater stability of collapse phases of DPPC/SP-B films prepared by spreading from liposomes in comparison to those spread from solvents can be interpreted as a consequence of formation of complex bilayer-monolayer interacting systems.

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Design and construction of an epifluorescence microscopic surface balance for the study of lipid monolayer phase transitions

Cited by 37 publications

References 11 publications

Spontaneous formation of interfacial lipid-protein monolayers during adsorption from vesicles

Spontaneous formation of interfacial lipid-protein monolayers during adsorption from vesicles

Segregation of Saturated Chain Lipids in Pulmonary Surfactant Filmsand Bilayers

Microstructure and dynamic surface properties of surfactant protein SP-B/dipalmitoylphosphatidylcholine interfacial films spread from lipid-protein bilayers

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