Unsaturation of serine lipids modulating the interaction of a cytosporone with models of the external leaflet of tumorigenic cell membranes.

Cytosporone-B was isolated from fungi and incorporated in models of tumorigenic cell membranes using palmitoyloleoylglycerophosphoserine (POPS) and dipalmitoyl glycerophosphoserine (DPPS) lipids. While for DPPS, the compound condensed the monolayer and decreased the surface compressional modulus, it expanded and kept the compressional modulus for POPS. Hysteresis for compression-expansion cycles was more sensitive for POPS than for DPPS, while a high degree of destabilization was observed for POPS. As observed with infrared spectroscopy and Brewster angle microscopy, specific changes were selective regarding molecular organization and morphology. Atomic force microscopy for transferred monolayers as Langmuir-Blodgett films also confirmed such specificities. We believe these data can help understand the mechanism of action of bioactive drugs in lipid interfaces at the molecular level.

Peptidoglycans modulating the interaction of a bactericide compound with lipids at the air-water interface.

A known monoterpene, named γ-terpineol, was incorporated in mixed Langmuir monolayers composed of dipalmitoyl-phosphoethanolamine (DPPE) and peptidoglycans as a model of microbial membranes. Surface pressure and surface potential isotherms, dynamical surface rheology, Brewster angle microscopy (BAM), and infrared spectroscopy were employed to characterize the compound-membrane interactions. The compound expanded the monolayers denoting repulsive interactions. At 30 mN/m, the monolayer presented lower viscoelastic and in-plane elasticity parameters and an increased all-trans/gauche conformers ratio for the alkyl chains, confirming molecular order. The morphology of the monolayer was analyzed by BAM, which revealed a heterogeneous distribution of γ-terpineol along the mixed monolayer, which tends to segregate. In conclusion, the compound changes the thermodynamic, electric, rheological, morphological, and structural properties of the peptidoglycan-DPPE monolayer, which may be essential to understand, at the molecular level, the action of bioactives in selected membrane models.

The effect of the monocyclic monoterpene tertiary alcohol γ-terpineol on biointerfaces containing cholesterol.

The compound γ-terpineol, which presents potential as microbicide and anticancer drug, was incorporated in cholesterol Langmuir monolayers, pure or mixed with DPPC. The compound expands the monolayers at higher molecular areas, but condenses them at lower areas, indicating a structural molecular rearrangement of γ-terpineol at the-water interface upon compression. Such effect was confirmed with rheological, surface potential, Brewster angle microscopy and infrared data, which indicated, respectively, reduction of the compressional modulus of the lipid monolayer, decrease of the surface potential, formation of aggregates, and alteration of the trans/gauche conformers ratio for methylene groups. Distinctive effects were observed for cholesterol monolayers without or with the presence of DPPC. Such results may help understand how the interaction of γ-terpineol with lipidic surfaces is modulated by lipids able to mediate the packing state of biointerfaces.

Interfacial vibrational spectroscopy and Brewster angle microscopy distinguishing the interaction of terpineol in cell membrane models at the air-water interface.

In this paper, γ-terpineol, a known monoterpene with biological activity, including in lipidic interfaces, was incorporated in Langmuir monolayers of selected phospholipids as a model for cellular membranes. Surface pressure-area isotherms showed that selected amounts of γ-terpineol expand DPPC and DPPE monolayers and decreased the monolayer elasticity, confirming the lipid/compound interaction. Characterization with vibrational spectroscopy and Brewster angle microscopy pointed that γ-terpineol adsorbs on the polar heads of the phospholipids, affecting the gauche conformations of the aliphatic chains, and different patterns were observed for DPPC and DPPE monolayers, indicating a characteristic molecular accommodation of γ-terpineol along the polar head of the phospholipids. Therefore, distinctive interactions with DPPC and DPPE could be observed regarding the incorporation of γ-terpineol with each lipid, leading to particular molecular arrangements at the air-water interface and pointing the modulation of the interaction according to the chemical composition of the monolayer.