Molecular organization in cholesterol-lecithin bilayers by x-ray and electron diffraction measurements

Location of Cholesterol in Liposomes by Using Small-angle X-ray Scattering (SAXS) Data and the Generalized Indirect Fourier Transformation (GIFT) Method

“…SAXS peaks of both samples were positioned at a q ratio of 1:2:3 owing to the lamellar structure with the identical face-to-face distance in the small-angle region. By contrast, the Chol system also showed a narrow peak q 14.7 nm 1 and a broad peak q 15.2 nm 1 in the wide-angle region, which are characteristic of the L β phase 25,26 , whereas the Chol system showed a single broader peak. The addition of Chol to phospholipids compacts the packing of the phospholipid acyl chain, which increases the freedom of acyl chains because the range of the phase transition temperature is broadened and T c starting point shifts toward lower temperatures 11 13 .…”

Modulation of the bilayer thickness of exocytic pathway membranes by membrane proteins rather than cholesterol

“…Analogously to simple model bilayers, acyl chain ordering in biological membranes has been extrapolated to effect an increase in membrane thickness. According to data obtained from model phospholipid͞cholesterol bilayers, molar cholesterol to phospholipid ratios of 0.12 and 1 should lead to increases in bilayer thickness of 2 and 7 Å, respectively, compared with systems with no cholesterol (18)(19)(20). Thus, the predicted decrease in bilayer thickness on cholesterol depletion would have been Ϸ2 Å (instead of Յ1 Å) for ER and Golgi membranes and Ϸ5 Å (instead of Յ1 Å) for basolateral and apical plasma membranes, given cholesterol-tophospholipid molar ratios of 0.08-0.1, 0.16-0.2, and 0.4-0.76, respectively (22,(48)(49)(50)(51).…”

“…Additionally, cholesterol has also been shown to affect the thickness of artificial bilayer systems in vitro. Extensive experimental and computational data for pure phospholipid͞cholesterol systems have demonstrated that, under certain circumstances, cholesterol increases bilayer thickness (18)(19)(20), presumably due to the ordering of the acyl chains of phospholipids. Because cholesterol is ubiquitous in eukaryotic cell membranes, it has been suggested that cholesterol is a principal modulator of bilayer thickness in these cells.…”

On the phase diagram of an L‐dipalmitoylphosphatidylcholine/cholesterol mixture

“…However, there is no consent on the size and pattern of the compositional domains in the plane of the membrane. For example, two different points of view oppose a phase separation in the gel phase into a phase of almost pure PC and a mixed PC-Chol phase at about 20-25 mol% Chol [3][4][5] against an ordered single-phase mixture of PC and Chol [6].…”