Membrane Models and Experiments Suitable for Studies of the Cholesterol Bilayer Domains

Abstract

Cholesterol (Chol) is an essential component of animal cell membranes and is most abundant in plasma membranes (PMs) where its concentration typically ranges from 10 to 30 mol%. However, in red blood cells and Schwann cells, PMs Chol content is as high as 50 mol%, and in the PMs of the eye lens fiber cells, it can reach up to 66 mol%. Being amphiphilic, Chol molecules are easily incorporated into the lipid bilayer where they affect the membrane lateral organization and transmembrane physical properties. In the aqueous phase, Chol cannot form free bilayers by itself. However, pure Chol bilayer domains (CBDs) can form in lipid bilayer membranes with the Chol content exceeding 50 mol%. The range of Chol concentrations surpassing 50 mol% is less frequent in biological membranes and is consequently less investigated. Nevertheless, it is significant for the normal functioning of the eye lens and understanding how Chol plaques form in atherosclerosis. The most commonly used membrane models are unilamellar and multilamellar vesicles (MLVs) and supported lipid bilayers (SLBs). CBDs have been observed directly using confocal microscopy, X-ray reflectometry and saturation recovery electron paramagnetic resonance (SR EPR). Indirect evidence of CBDs has also been reported by using atomic force microscopy (AFM) and fluorescence recovery after photobleaching (FRAP) experiments. The overall goal of this review is to demonstrate the advantages and limitations of the various membrane models and experimental techniques suitable for the detection and investigation of the lateral organization, function and physical properties of CBDs.

Resveratrol Liposomes for Buccal Formulations: Suitability for Chemoprevention and Treatment of Oral Cancer

“…According to our results, RSV molar fractions ≥ 0.3 lead to RSV excess retained in the filter during the extrusion process. According to this finding, molecular packing restriction for RSV in lipid EPC bilayer seems to be different that reported for CHOL, the latter able to incorporate into lipid bilayers up to 0.5-0.6 molar fraction (42).…”

“…The permeability assay was carried out with liposomes produced from 0.3 molar fraction and 1.98 mg/mL RSV concentration with or without vitamin C. PermeaPad® membranes were used in this study because these have proven functionality in predicting drug transport across biological barriers, including buccal epithelium (42). Figure 6 shows the mean cumulative amounts of RSV quantified in the receptor compartment of the diffusion cell (individual values in figure S2 of supplementary material).…”

Enhancing Bovine Embryo Development In Vitro Using Oil-in-Water Nanoemulsions as Specific Carriers for Essential Lipids

“…This means that cholesterol had an important surfactant effect in this system. This phenomenon could be attributed to the surfactant-like amphiphilic nature of cholesterol, since its structure consists of a sizable, nonpolar rigid planar fused-ring structure featuring a smooth side and a rough side, along with a brief flexible isooctyl tail and a small hydrophilic moiety in the form of a hydroxyl (−OH) group [ 31 , 32 ].…”

Anisotropia de fluorescência da sonda AHBA em lipossomas de misturas lipídicas e contendo colesterol

“…bem como para o desenvolvimento de novos fármacos capazes de atuar em membranas. Dada a complexidade natural das membranas celulares, sistemas modelos como micelas de surfactantes e vesículas fosfolipídicas são amplamente utilizados em estudos biofísicos e bioquímicos (1)(2)(3)(4)(5).…”