Investigations of monolayers by fluorescence microscopy

Stine, Keith J.

doi:10.1002/jemt.1070270510

Cited by 28 publications

(24 citation statements)

References 73 publications

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“…Dark domains generally indicate a liquid-condensed phase in lipid monolayers (Knobler, 1990;Stine, 1994). Fractallike lipid domains have been previously observed with fluorescence microscopy in phospholipid monolayers.…”

Section: Discussionmentioning

confidence: 82%

Atomic Force Microscopy of Nonhydroxy Galactocerebroside Nanotubes and Their Self-Assembly at the Air–Water Interface, with Applications to Myelin

Ohler

Revenko

Husted

2001

Journal of Structural Biology

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Myelin is one of the few biological membranes to contain the lipid galactocerebrosides, although their role in myelin is unclear. To explore its structural role, we used fluorescence and atomic force microscopy (AFM) to study nonhydroxy galactocerebrosides (NCer) at the air-water interface of a Langmuir-Blodgett trough. Fluorescence microscopy at the air-water interface indicated that NCer forms micrometer scale domains of varying radii with six fractal-like extensions. Atomic force microscopy using TappingMode in water on samples transferred to mica confirmed the fractal-like domain structure in the absence of dye and showed that the domains consisted of many aggregated nanotubes with a diameter of 30 nm. The Hausdorf fractal dimension was estimated to be 1.26 and 1.11 for two domains imaged with AFM. This evidence indicates that NCer forms a bulk phase of nanotubes at the air-water interface, unlike the liquidcondensed phase of a phospholipid monolayer. That NCer forms bilayer nanotubes that aggregate strongly suggests NCer helps maintain the stability of myelin by contributing to the curvature and adhesion of the membrane. We found that NCer appears to be decreased in myelin from multiple sclerosis normal appearing white matter, which could be an important event in the loss of myelin stability.

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Section: Discussionmentioning

confidence: 82%

Atomic Force Microscopy of Nonhydroxy Galactocerebroside Nanotubes and Their Self-Assembly at the Air–Water Interface, with Applications to Myelin

Ohler

Revenko

Husted

2001

Journal of Structural Biology

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“…Any deviations from the characteristics observed in DPPC and DPPG isotherms obtained in the absence of P188 are attributed to the presence of P188 at the air-water interface. ence (Andelman et al, 1994;Kaganer et al, 1999;Knobler and Desai, 1992;Lee et al, 1998;Lipp et al, 1997;Mc-Connell, 1991;Möhwald, 1990Möhwald, , 1993Stine, 1994;Weis, 1991). As the surface area for each molecule was reduced, the onset of the LE/LC phase transition occurred at 20 mN/for DPPC, and at 6 mN/m for DPPG, each lipid forming condensed domains in a LE background.…”

Section: Lateral Compression Resultsmentioning

confidence: 99%

Direct Observation of Poloxamer 188 Insertion into Lipid Monolayers

Maskarinec

Hannig

Lee

et al. 2002

Biophysical Journal

206

215

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P188, a triblock copolymer of the form poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) helps seal electroporated cell membranes, arresting the leakage of intracellular materials from the damaged cells. To explore the nature of the interaction between P188 and cell membranes, we have constructed a model system that assesses the ability of P188 to insert into lipid monolayers. Using concurrent Langmuir isotherm and fluorescence microscopy measurements, we find that P188 changes the phase behavior and morphology of the monolayers. P188 inserts into both dipalmitoylphosphatidlycholine and dipalmitoylphosphatidylglycerol monolayers at surface pressures equal to and lower than approximately 22 mN/m at 30 degrees C; this pressure corresponds to the maximal surface pressure attained by P188 on a pure water subphase. Similar results for the two phospholipids indicate that P188 insertion is not influenced by headgroup electrostatics. Because the equivalent surface pressure of a normal bilayer is on the order of 30 mN/m, the lack of P188 insertion above 22 mN/m further suggests the poloxamer selectively adsorbs into damaged portions of electroporated membranes, thereby localizing its effect. P188 is also found to be "squeezed out" of the monolayers at high surface pressures, suggesting a mechanism for the cell to be rid of the poloxamer when the membrane is restored.

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“…In the first, the initial period of constant tension is due to a gaseous/liquid phase transition in the monolayer that occurs during adsorption. While the phase behavior of bulk soluble surfactants has not been extensively studied, polymorphism in insoluble monolayers spread and compressed at the air/water interface of a Langmuir trough has been well documented by surface pressure/area (9), fluorescence (10) and Brewster angle microscopy (11)(12)(13), X-ray (14) and electron diffraction (15), and neutron reflectivity (16)(17)(18). It is generally recognized that for medium-to long-hydrocarbon-chain-length (e.g., [16][17][18][19][20] carbons) insoluble alcohols and carboxylic acids at room temperature, monolayers exist (in order of increasing density) in a dilute gaseous state (G), an amorphous liquid expanded (LE) phase, liquid condensed (LC) phases in which the chains are tilt ordered, and a solid (LS) state with vertical chains and positional ordering of the head group.…”

Section: Introductionmentioning

confidence: 99%