Effect of cholesterol content on the structural and dynamic membrane properties of DMPC/DSPC large unilamellar bilayers

Abstract

In this study, we report the effect of cholesterol content on the dynamic and structural properties of a dimyristoyl-phosphatidylcholine and distearoyl-phosphatidylcholine mixture in large unilamellar vesicles. The range of cholesterol concentrations studied varied around approximately 33.3mol%, where it has been postulated that an abrupt change in bilayer organization occurs. Steady-state fluorescence measurements demonstrated a typical behavior; at low temperatures in the main phase transition, the cholesterol concentration did not affect the gel phase, but at 37.5°C (phase coexistence) and in the liquid crystalline phase, the presence of cholesterol produced an increase in the fluorescence anisotropy of DPH and the generalized polarization of Laurdan. The greater effect was observed in the liquid crystalline phase, in which the bilayer became a mixture of fluid-like and liquid-ordered phases. The results obtained at approximately 33.3mol% of Cholesterol demonstrated that the Generalized Polarization of Laurdan, the DPH lifetime, the limiting anisotropy and the rotational correlation time, as well as the fluorescence quenching of DPH by TEMPO, are at maxima, while the fluorescence intensity of dehydroergosterol and the lipid solubility in TritonX-100 are at minima. These results correlate well with the hypothesis of domain segregation in the DMPC/DSPC/Cholesterol LUV system. In this context, we postulate that at 33.3mol% of Cho, the proportion of ordered domains reaches a maximum.

Atomic Force Microscopic Analysis of the Effect of Lipid Composition on Liposome Membrane Rigidity

“…In this regard, quantitative AFM analysis is advantageous over the conventional qualitative method that uses the Laurdan GP value because the Laurdan method cannot capture the difference in membrane rigidity, especially for liposomes containing saturated lipids and Chol in the So or Lo phase (Figure B). The absence of a notable effect of Chol content on the GP value of Laurdan in Lo- and So-phase liposomes containing saturated lipids such as dimyristoyl­phosphatidyl­choline (DMPC), DPPC, or DSPC has also been reported previously. , …”

“…The absence of a notable effect of Chol content on the GP value of Laurdan in Lo-and So-phase liposomes containing saturated lipids such as dimyristoylphosphatidylcholine (DMPC), DPPC, or DSPC has also been reported previously. 55,56 Chol content is important not only for improving liposomal stability 7 but also for enhancing the gene transfection efficiency of liposomes such as DOTAP liposomes. 5 The several studies using giant unilamellar vesicles have reported the effects of cholesterol on bending rigidity.…”

Label-Free Macroscopic Fluorescence Lifetime Imaging of Brain Tumors

“…Tyrosine and tryptophan are major aminoacids that constitute myelin sheath but their excitation bands are around 280 nm, which is far away from the excitation wavelength for NAD(P)H. Therefore, only lipids with the excitation wavelengths around 340-400 nm and detection in the spectral range of 400-500 nm may be responsible for the long fluorescence lifetime. Indeed, cholesterol, one of the major components of lipids, is known to have long fluorescence lifetimes on the order of 9 ns ( 46 , 47 ). Moreover, time-resolved measurements of fluorescence from phospholipids, another major component of lipids, showed fluorescence lifetimes in the range from 7.0 to 12.0 ns, depending on the microenvironment ( 48 ).…”

A designed lipopeptide with a leucine zipper as an imbedded on/off switch for lipid bilayers

“…There was no obvious phase transition point on these curves, which was thought to result from the high content of cholesterol in the bilayer. 31 However, the data could be used to compare the fluidity of the membranes under various temperatures. Lipo-LPe showed higher r values than pure liposomes through almost the entire temperature range, indicating that the insertion of lipopeptides helped improve the stability of the liposomal bilayer.…”