Sterols interactions

In another study, the in vitro modulation of rat adipocyte ghost membrane fluidity by cholesterol oxysterols was investigated [55]. It was found that cholesterol oxy-sterols interact differently with rat adipocyte membranes. Cholestanone interacts predominantly with the phospholipids located at the inner leaflet (e.g. PE), whereas cholesterol interacts preferably with the phospholipids (PC) of the outer layer. 

The effect of cholesterol on the thermotropic phase behavior of PC bilayer also varies significantly with the structure, particularly the degree of unsaturation, of the hydrocarbon chains, with more highly unsaturated PCs exhibiting a reduced miscibility with cholesterol and other sterols. Moreover, the structure of the lipid polar headgroup is also important in determining the effect of cholesterol on the host lipid, as is the structure of the sterol molecule itself. For more information on the application of DSC to the biologically important area of lipid-sterol interactions, the reader is referred to recent reviews (23-25). 

AndreollTE. On the anatomy of amphotericin B-cholesterol pores in lipid bilayer membranes. Kidney Int 1973 4 337-45. DeKruijiff B, Demel RA. Polyene antibiotic-sterol interactions in membranes of Acholeplesma laidlawii cellsand lecithin liposomes. III. Molecular structure of the polyene antibiotic-cholesterol complexes. Biochem Biophys Acta 1974 339 57-70. HoIzRW.Theeffectsofthe polyene antibiotics nystatin and amphotericin Bon thin lipid membranes. Ann N Y Acad Sell 974 235 469-79. 

Polyene-sterol interaction has been demonstrated in vitro... 

The polyene sterol interaction did not merely nullify the effect of sterol addition. Polyenes appeared to combine with liposome sterols and this combination destroyed the permeability properties of the liposome. 

It is interesting to note than the structural requirement for the maximal interaction between sterols and lecithin monolayers [196] and for sterol-mediated reduction of liposome permeability [179] are a 3j3-hydroxyl group, a planar sterol nucleus and an intact C17 sidechain, which is identical with the requirement for maximal polyene sterol interaction [101,146]. 

Whether phase transition changes are directly responsible for the permeability changes observed in liposomes and bilayers is debatable but results obtained by DSC are indicative that polyene addition to sterol-containing liposomes, bilayers or membranes markedly alters the molecular structure of the membrane by reducing the phospholipid-sterol interaction. Such alterations may be the basis for the observed polyene-mediated permeability changes to ions and small nonelectrolytes [ 101,103-106,201 -212,216]. 

C.-H. Huang, Roles of Carbonyl Oxygens at the Bilayer Interface in Phospholipid-Sterol Interaction, Nature 259, 242-244 (1976). 

Researchers have studied whether acyl-chain order could be responsible for the preferred sterol interaction with SMs. Acyl-chain order was deduced from diphenylhexatriene anisotropy and from the deuterium order parameter obtained by H-NMR on bilayers made from either 14 0/14 0(d27)-PC, or 14 0(d27)-SM7 Some researcher analyzed the ground and excited states of phospholamban (PLN), a membrane protein that regulates sarcoplasmic reticulum (SR) calcium ATPase (SERCA), in dilferent membrane mimetic environments. Gustavsson et al. have previously proposed that the conformational equilibrium of PLN are central to SERCA regulation. They have now shown that these equilibrium detected in micelles and bicelles are also present in native sarcoplasmic reticulum lipid membranes as probed by MAS solid-state NMR. ... 

Sterol Interaction with tubule membranes leads to chloride leakage reduced rertal blood flow, and deceased CFR... 

A number of people who were attending the Symposium for the first time commented on the open and friendly atmosphere. There is a family feeling since the community of people who work on plant lipids is still fairly small. At this Symposium however, there were several friends of the family, people accustomed to reporting their research in other areas who have much to contribute to the field of plant lipids. We think in particular of the contribution of Leo Parks on the function of sterols in yeast, the presentation of Joe Kuc on the importance of lipids in host-pathogen interactions, and the paper of Rudy Demel on the dynamics of glycerolipid, sphingolipid and sterol interaction in membranes. 

Mannock, D.A., Lewis, R.N.A.H., McMullen, T.P.W., and McElhaney, R.N. (2010) The effect of variations in phospholipid and sterol structure on the nature of lipid-sterol interactions in lipid bilayer model membranes. Chem. Phys. Lipids, 163, 403—448. 

Cholesterol in membrane bilayers has an important modulatory effect on the bilayer phase of phospholipids [2,15]. The sterol interacts strongly with phospholipids and keeps them in an intermediate fluid condition. Thus, above its transition temperature, the presence of cholesterol tends to increase the packing and rigidity of bilayers [19], and below its transition temperature, it expands and fluidizes the bilayers [20]. 

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