Optical studies of lecithin-membrane melting

Harbich, W.; Servuss, R.M.; Helfrich, W.

doi:10.1016/0375-9601(76)90071-2

Cited by 36 publications

(28 citation statements)

References 8 publications

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“…The formation occurs either spontaneously [1,9] or under slight and probably immaterial agitation [11,12], Also, the complete mathematical analysis [13,14] of photographed shapes of axi-symmetric, oblate vesicles of egg lecithin whose membrane was in contact with itself over a certain area did not provide any evidence of mutual attraction. The membranes of these vesicles were judged from experience to consist of only a few bilayers.…”

Section: Discussionmentioning

confidence: 95%

“…The derivation of the entrop} 7 ASq per mode is not so easy and, perhaps, preferably done in terms of real sinusoidal rather than complex modes. We may express the new modes by the old aq cos q r = uq e iqr -u_qe 1 bq sin q r = i(uq e iqr -u_qe~ (8) recalling that uq = u_q. Denoting the amplitude of some sinusoidal mode simply by a, we may write for the Gaussian…”

Section: Theory Employing Smectic Compressibilitymentioning

confidence: 99%

“…Fluid membranes undergo out-of-plane fluctuations analyzable in terms of undulation modes. The out-of-plane fluctuations of lecithin membranes reveal themselves in the slight and constantly changing bumpiness of large thinw-alled vesicles observed under a phase contrast microscope [1]. Undulation modes have also found some theoretical attention [2,3], one reason being that the ripples may use up a small fraction of the effective membrane area.…”

Section: Introductionmentioning

confidence: 99%

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Steric Interaction of Fluid Membranes in Multilayer Systems

Helfrich

1978

Zeitschrift Für Naturforschung A

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1,056

435

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The out-of-plane fluctuations of fluid membranes are sterically hindered in multilayer systems. The repulsive interaction associated with the steric or excluded-volume effect is studied theoretically by two methods. The interaction energy per unit area of membrane is derived as a function of temperature, membrane curvature elasticity and mean membrane spacing; it is inversely proportional to the square of the latter. Steric repulsion is estimated for lecithin bilayers in water. There and in other cases, it may compete with van der Waals attraction.

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Section: Discussionmentioning

confidence: 95%

Section: Theory Employing Smectic Compressibilitymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Steric Interaction of Fluid Membranes in Multilayer Systems

Helfrich

1978

Zeitschrift Für Naturforschung A

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435

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“…The adhesive behaviour of tension-free and, later, slightly stressed lecithin membranes has been investigated with optical microscopy in our group. In a large excess of water, lecithins above the main transition temperature always swelled and usually disintegrated, forming giant, often unilamellar vesicles in the process [7][8][9][10]. Furthermore, vesicles displaying well visible undulations (up to 10 % of the radius for spheres) were never seen to adhere on collisions [9].…”

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confidence: 99%

Mutual adhesion of lecithin membranes at ultralow tensions

1989

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2014 On présente une étude par microscopie optique de l'adhésion mutuelle de doubles couches de lécithine d'0153uf ou dimyristoyl dans des échantillons très gonflés. Les tensions latérales permettant l'adhésion, en dessous de 3 x 10-4 dyn cm-1, sont déterminées à partir de la courbure de la membrane à proximité de la zone de contact. L'angle de contact maximal des deux membranes soumises à des tensions égales à une valeur maximale de 45°. En dépit de quelque dispersion, cet angle ne semble pas dépendre de la tension jusqu'à sa valeur observable la plus faible, 3 x 10-6 dyn cm-1. L'angle de contact maximal d'une membrane isolée adhérant à un ensemble de membranes est proche de 70°. Les données indiquent que l'adhésion mutuelle est toujours induite par la tension latérale. La valeur constante des angles de contact semble compatible avec la théorie des ondulations, mais cette valeur nous pousse à postuler une rugosité de la membrane, non détectable optiquement, qui servirait de réserve d'aire. Abstract. 2014 We present an extensive light-microscopic study of mutual adhesion of egg (and dimyristoyl) lecithin bilayers in highly swollen samples, including adhesion brought about by osmotic inflation of vesicles. The lateral tensions associated with adhesion, if below ca. 3 x 10-4 dyn cm-1, could be read from a rounding of the membrane next to the contact area. The contact angle of symmetric adhesion, i.e. of two membranes under equal tension, had a maximum of 45°. While showing some scatter, it did not seem to depend on tension down to 3 x 10-6 dyn cm-1, the lowest tension observed. The maximum contact angle of single membranes adhering to bundles of membranes was near 70°. The data indicate that mutual adhesion of lecithin membranes is always induced by lateral tension. The constancy of the contact angles appears to be compatible with undulation theory, but their magnitude compels us to postulate an unknown, optically unresolvable roughness of lecithin membranes which serves as an area reservoir.

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“…Large thin-walled vesicles with radii mostly between 5 and 50 ,m were prepared by simple swelling as described elsewhere (9,10). Subsequently, they were allowed to stand for several days.…”

Section: Methodsmentioning

confidence: 99%

Osmotic Shrinkage of Giant Egg-Lecithin Vesicles

Elwenspoek¹,

Boroske²,

Helfrich³

1980

Springer Series in Chemical Physics

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Osmotic shrinkage of giant egg-lecithin vesicles was observed by phase-contrast microscopy. The vesicles remained or became spherical when shrinking. Small and thickwalled vesicles formed visible fingers attached to the sphere. The water permeability of the single bilayer was found to be 41 ,m/s. A variety of observations indicate that osmosis induces a parallel lipid flow between the monolayers of the bilayer, leading to a strong positive spontaneous curvature. They also suggest the formation of mostly submicroscopic daughter vesicles. The estimated coupling constant, 2 * 10-6 mol/mol, is large enough to be biologically significant.

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Optical studies of lecithin-membrane melting

Cited by 36 publications

References 8 publications

Steric Interaction of Fluid Membranes in Multilayer Systems

Steric Interaction of Fluid Membranes in Multilayer Systems

Mutual adhesion of lecithin membranes at ultralow tensions

Osmotic Shrinkage of Giant Egg-Lecithin Vesicles

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