PubMed · 10810921
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P K Kinnunen. 1999. Peripheral interactions on lipid membrane surfaces.. https://doi.org/10.1016/s0009-3084(99)00051-1
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We study the dynamics and final wetting state of skin lipids on water and brine by fluorescence microscopy and ellipsometry. When a lipid droplet is brought into contact with the water surface, a lipid wetting film spreads out rapidly by a Marangoni effect. Subsequently, this film undergoes a dewetting instability. However, the final equilibrium is not partial wetting. The film breaks up into droplets with a mesoscopic (approximately 50 A) film in between. These observations result from a subtle interplay between short- and long-range forces: surfactants naturally present in the lipids favor wetting, while the van der Waals forces oppose it. In addition, this reveals the likely organization of the hydrolipid film that covers and protects the skin.
Lipid-modified proteins play decisive roles in important biological processes such as signal transduction, organization of the cytoskeleton, and vesicular transport. Lipidated peptides embodying the characteristic partial structures of their parent lipidated proteins and semisynthetic proteins synthesized from such peptides are valuable tools for the study of these biological phenomena. We have developed an efficient synthesis strategy that allows for the synthesis of long multiply lipidated peptides embodying various side chain functional groups. The strategy was successfully applied in the synthesis of the N-terminal undetrigintapeptide of endothelial NO-synthase and related lipopeptides. Key elements of the synthesis strategy are the combined use of the enzyme-labile para-phenylacetoxybenzyloxycarbonyl (PhAcOZ) urethane as N-terminal blocking group, the Pd0-sensitive allyl ester as C-terminal protecting function and acid-labile side chain protecting groups for solution-phase synthesis of labile S-palmitoylated building blocks under the mildest conditions with solid-phase techniques and solution-phase fragment condensations. The successful synthesis of the triply lipidated 29-mer eNOS peptide convincingly demonstrates the full capacity of the protecting group methods.
In dealing with the passive transport of organic contaminants from soils to plants (including crops), a partition-limited model is proposed in which (i) the maximum (equilibrium) concentration of a contaminant in any location in the plant is determined by partition equilibrium with its concentration in the soil interstitial water, which in turn is determined essentially by the concentration in the soil organic matter (SOM) and (ii) the extent of approach to partition equilibrium, as measured by the ratio of the contaminant concentrations in plantwater and soil interstitial water, alphapt (< or = 1), depends on the transport rate of the contaminant in soil water into the plant and the volume of soil water solution that is required for the plant contaminant level to reach equilibrium with the external soil-water phase. Through reasonable estimates of plant organic-water compositions and of contaminant partition coefficients with various plant components, the model accounts for calculated values of alphapt in several published crop-contamination studies, including near-equilibrium values (i.e., alphapt approximately equals 1) for relatively water-soluble contaminants and lower values for much less soluble contaminants; the differences are attributed to the much higher partition coefficients of the less soluble compounds between plant lipids and plant water, which necessitates much larger volumes of the plant water transport for achieving the equilibrium capacities. The model analysis indicates that for plants with high water contents the plant-water phase acts as the major reservoir for highly water-soluble contaminants. By contrast, the lipid in a plant, even at small amounts, is usually the major reservoir for highly water-insoluble contaminants.