Microcrystallinity of Solid-State Langmuir-Blodgett Films of Saturated Fatty Acids Studied by Scanning Force Microscopy and Brewster Angle Microscopy

Wolthaus, L.; Schaper, A.; Moebius, D.

doi:10.1021/j100093a022

Cited by 21 publications

(11 citation statements)

References 11 publications

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“…This is also in agreement with the differences in monolayer thickness of -5 A that we found in the ECerHlI-Chol mixed monolayers. The expected difference in thickness is somewhat greater because the difference in fatty acid chain length is 6 C atoms, but that can be explained by the depression of the monolayer by the AFM tip (Wolthaus et al, 1994). At cholesterol concentrations higher than 1:1 the interaction between cholesterol and the long-chain :CerIII fraction has become high enough to incorporate the longchain XCerIII fraction into the mixed short-chain ECerIII fraction-cholesterol phase, resulting in one homogeneous phase.…”

Section: Mixtures Of Ceramides and Cholesterolmentioning

confidence: 99%

Phase behavior of stratum corneum lipids in mixed Langmuir-Blodgett monolayers

Grotenhuis

Demel

Ponec

et al. 1996

Biophysical Journal

112

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The lipids found in the bilayers of the stratum corneum fulfill the vital barrier role of mammalian bodies. The main classes of lipids found in stratum corneum are ceramides, cholesterol, and free fatty acids. For an investigation of their phase behavior, mixed Langmuir-Blodgett monolayers of these lipids were prepared. Atomic force microscopy was used to investigate the structure of the monolayers as a function of the monolayer composition. Three different types of ceramide were used: ceramide extracted from pigskin, a commercially available ceramide with several fatty acid chain lengths, and two synthetic ceramides that have only one fatty acid chain length. In pigskin ceramide-cholesterol mixed monolayers phase separation was observed. This phase separation was also found for the commercially available type III Sigma ceramide-cholesterol mixed monolayers with molar ratios ranging from 1:0.1 to 1:1. These monolayers separated into two phases, one composed of the long fatty acid chain fraction of Sigma ceramide III and the other of the short fatty acid chain fraction of Sigma ceramide III mixed with cholesterol. Mixtures with a higher cholesterol content consisted of only one phase. These observations were confirmed by the results obtained with synthetic ceramides, which have only one fatty acid chain length. The synthetic ceramide with a palmitic acid (16:0) chain mixed with cholesterol, and the synthetic ceramide with a lignoceric acid (24:0) chain did not. Free fatty acids showed a preference to mix with one of these phases, depending on their fatty acid chain lengths. The results of this investigation suggest that the model system used in this study is in good agreement with those of other studies concerning the phase behavior of the stratum corneum lipids. By varying the composition of the monolayers one can study the role of each lipid class in detail.

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Section: Mixtures Of Ceramides and Cholesterolmentioning

confidence: 99%

Phase behavior of stratum corneum lipids in mixed Langmuir-Blodgett monolayers

Grotenhuis

Demel

Ponec

et al. 1996

Biophysical Journal

112

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“…Traditionally information on the organization of the monolayers has been obtained from surface pressure-area isotherms. During the past decade more sophisticated methods have been developed such as fluorescence microscopy, 1 Brewster-angle microscopy (BAM), 2 and synchrotron X-ray diffraction, 3 which provide a much more detailed picture of the molecular organization in the monolayer. However, these methods show a limited lateral resolution of structures existing in the plane of the film.…”

Section: Introductionmentioning

confidence: 99%

An AFM Study of Lipid Monolayers. 1. Pressure-Induced Phase Behavior of Single and Mixed Fatty Acids

et al. 1999

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Monolayers of palmitic (C16:0) and lignoceric acid (C24:0) and their equimolar mixture were transferred to a hydrophilic mica substrate at various surface pressures and investigated by means of atomic force microscopy (AFM) in contact and lateral force modes. The first-order transition of lignoceric acid gives a plateau region, representing a liquid expanded to liquid condensed phase transition in the pressure-area isotherm. This was visualized by AFM as stripes of a condensed phase within the expanded phase, exhibiting a small height difference but a significant difference in friction. The corresponding phase transition of the palmitic acid was continuous, and no changes of the Langmuir-Blodgett films with respect to pressure were observed with AFM. Both the surface pressure-area isotherms and the direct observations of domains of irregular size and shape using the AFM showed that lignoceric and palmitic acid were immiscible. The height difference between the domains was 1.1 nm corresponding to the difference in hydrocarbon chain length of the two fatty acids.

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“…Two-dimensional phase separations and phase transitions in LB films have therefore been intensively studied. Classically, the phase behavior of surfactant mixtures at the gas−liquid interface has been characterized by means of surface pressure−area isotherms. , Fluorescence microscopy, Brewster-angle microscopy, and X-ray diffraction have also been used to study lateral arrangement of lipids at the interface, although none of these techniques can provide information on heterogeneous domain formation as well as on nanometer scale structures. AFM is a surface imaging technique with very high lateral resolution.…”

Section: Introductionmentioning

confidence: 99%

An AFM Study of Lipid Monolayers. 2. Effect of Cholesterol on Fatty Acids

et al. 1999

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In this study the effect of cholesterol in Langmuir-Blodgett monolayers of fatty acids of varying chain lengths was investigated by atomic force microscopy (AFM). Domain formation due to lateral phase separation was studied at different lipid compositions and surface pressures. A small amount of cholesterol is miscible with palmitic acid (C16:0) and forms a flat monolayer while excess cholesterol forms a rougher cholesterolrich phase. No miscibility was observed in monolayers of lignoceric acid (C24:0) and cholesterol. For the ternary mixed monolayer (palmitic acid, lignoceric acid, and cholesterol) the two fatty acids formed separate domains and the miscibility of cholesterol in the two phases showed behavior corresponding to that of the binary fatty acid-cholesterol systems. From the shape, size, and height differences of the domains one can conclude that the driving force to minimize the interfacial length between different phases is reduced in the presence of cholesterol. This can be attributed to line active properties of cholesterol.

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Microcrystallinity of Solid-State Langmuir-Blodgett Films of Saturated Fatty Acids Studied by Scanning Force Microscopy and Brewster Angle Microscopy

Cited by 21 publications

References 11 publications

Phase behavior of stratum corneum lipids in mixed Langmuir-Blodgett monolayers

Phase behavior of stratum corneum lipids in mixed Langmuir-Blodgett monolayers

An AFM Study of Lipid Monolayers. 1. Pressure-Induced Phase Behavior of Single and Mixed Fatty Acids

An AFM Study of Lipid Monolayers. 2. Effect of Cholesterol on Fatty Acids

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