Hydrophilic/Hydrophobic Nanostripes in Lipopolymer Monolayers

Ahrens, H.; Baekmark, T. R.; Merkel, Rudolf; Schmitt, Johannes; Graf, Karlheinz; Raiteri, Roberto; Helm, Christiane A.

doi:10.1002/1439-7641(20000915)1:2<101::aid-cphc101>3.3.co;2-f

Cited by 23 publications

(97 citation statements)

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“…From the ellipsometric images, we observed no heterogeneity in the contact angle corresponding to the thickness and periodicity of the stripe patterns, suggesting that the phase separation of lipids and lipopolymers is not caused by the local heterogeneity of the three-phase contact line. This is in contrast to previous reports on lipid−lipopolymer membranes, in which packing mismatch between polymer head groups and hydrocarbon chains , or random grafting of polymer chains to surfaces caused topographic roughening of the membranes. It should be noted that the combination of a Langmuir film balance and an imaging ellipsometer is a powerful tool to spatially resolve the height profile of very thin ( h < micrometers) liquid films near the interface, which would not be accessible with other experimental techniques.…”

Section: Resultscontrasting

confidence: 99%

Dissipative Structure Formation in Lipid/Lipopolymer Monolayers

et al. 2011

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We study the formation of dissipative microstructures in monomolecular films of surfactant mixtures, which occur near the three-phase contact line during Langmuir-Blodgett transfer onto a solid substrate. Continuous stripes parallel to the transfer direction are generated over several centimeters, indicating the phase separation of phospholipids and lipids with polymer head groups (lipopolymers). The systematic variation of transfer conditions revealed that transfer speed and subphase viscosity determine the stripe-to-stripe distance from several micrometers to submicrometers. To account for the physical mechanism of such pattern formation, we characterize the local film thickness and the membrane composition in the vicinity of the three-phase contact line using imaging ellipsometry and fluorescence microscopy. At relatively slow rates of substrate lifting, the power law exponent that we found between the interstripe distance and the transfer speed suggests that the stripe formation is due to spinodal decomposition, which can be accounted under the framework of the Cahn-Hilliard equation, whereas at relatively high rates, the distance is found to be proportional to the substrate speed, suggesting a dominant effect of the shear force on the stripe formation.

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Section: Resultscontrasting

confidence: 99%

Dissipative Structure Formation in Lipid/Lipopolymer Monolayers

et al. 2011

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“…Additionally, the compression of the adsorbed polymer might affect the surface pressure. Transitions between different phases of polymeric monolayers have been observed in the past. ,, If the polymer monolayer undergoes a first-order transition, a plateau region in the isotherm is observed and a transition enthalpy can be determined. In some cases, the surface pressure of the disordered-to-ordered phase transition decreases with increasing molar mass for a given temperature.…”

Section: Resultsmentioning

confidence: 99%

Lipid Monolayers and Adsorbed Polyelectrolytes with Different Degrees of Polymerization

et al. 2014

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Polystyrene sulfonate (PSS) of different molecular weight M(w) is adsorbed to oppositely charged DODAB monolayers from dilute solutions (0.01 mmol/L). PSS adsorbs flatly in a lamellar manner, as is shown by X-ray reflectivity and grazing incidence diffraction (exception: PSS with M(w) below 7 kDa adsorbs flatly disordered to the liquid expanded phase). The surface coverage and the separation of the PSS chains are independent of PSS M(w). On monolayer compression, the surface charge density increases by a factor of 2, and the separation of the PSS chains decreases by the same factor. Isotherms show that on increase of PSS M(w) the transition pressure of the LE/LC (liquid expanded/liquid condensed) phase transition decreases. When the contour length exceeds the persistence length (21 nm), the transition pressure is low and constant. For low-M(w) PSS (<7 kDa) the LE/LC transition of the lipids and the disordered/ordered transition of adsorbed PSS occur simultaneously, leading to a maximum in the contour length dependence of the transition enthalpy. These findings show that lipid monolayers at the air/water interface are a suitable model substrate with adjustable surface charge density to study the equilibrium conformation of adsorbed polyelectrolytes as well as their interactions with a model membrane.

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“…We assume that the second kink is the onset of the liquid expanded/liquid condensed-transition of the phospholipids released from the oleosomes after rupture. Another possible explanation for this kink would be desorption of the oleosin proteins, comparable to the desorption transition of lipopolymers . However, for oleosins, such a behavior seems to be unlikely.…”

Section: Discussionmentioning

confidence: 99%

“…Another possible explanation for this kink would be desorption of the oleosin proteins, comparable to the desorption transition of lipopolymers. 37 However, for oleosins, such a behavior seems to be unlikely. First, the strong hydrophobicity suggests an aggregation to micelles, which would be stabilized in the subphase by the two hydrophilic tails of each oleosin.…”

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Soybean Oleosomes Behavior at the Air–Water Interface

et al. 2012

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Soy milk is a highly stable emulsion, the stability being mainly due to the presence of oleosomes or oil bodies, spherical structures filled with triacylglycerides (TAGs) and surrounded by a monolayer of phospholipids and proteins called oleosins. For oleosomes purified from raw soymilk, surface pressure investigations and Brewster angle microscopy have been performed to unveil their adsorption, rupture and structural changes over time at different subphase conditions (pH, ionic strength). Such investigations are important for (industrial) food applications of oleosomes, but are also useful for the understanding of the general behavior of proteins and phospholipids at interfaces. In addition a better comprehension of the highly stable oleosomes can lead to advancements in liposome manufacturing, e.g., for storage and transport applications. Although oleosomes have their origin in food systems, their unique stability and physical behavior show transferable characteristics which lead to a much better understanding of the description of any kind of emulsion. This study is one of the first steps toward the comparison of natural emulsification concepts based on different physical structures: e.g., the animals' low density lipoproteins, where apolipoproteins with phospholipids are located only at the interface and plant oleosomes with its oleosins, which are embedded in a phospholipid monolayer and reach deep inside the oil phase.

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Hydrophilic/Hydrophobic Nanostripes in Lipopolymer Monolayers

Cited by 23 publications

References 0 publications

Dissipative Structure Formation in Lipid/Lipopolymer Monolayers

Dissipative Structure Formation in Lipid/Lipopolymer Monolayers

Lipid Monolayers and Adsorbed Polyelectrolytes with Different Degrees of Polymerization

Soybean Oleosomes Behavior at the Air–Water Interface

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