Clustering of spin-labeled cholesterol analog diluted in bilayers of saturated and unsaturated phospholipids.

Clustering of spin-labeled cholesterol analog, 3β-doxyl-5α-cholestane (DChl), diluted in bilayers comprised of either saturated dipalmitoyl-glycero-phosphocholine (DPPC) or unsaturated dioleoyl-glycero-phosphocholine (DOPC) phospholipids was studied. DChl molar fraction X varied between 0.005 and 0.

Lipid-Mediated Clusters of Guest Molecules in Model Membranes and Their Dissolving in the Presence of Lipid Rafts.

The clustering of molecules is an important feature of plasma membrane organization. It is challenging to develop methods for quantifying membrane heterogeneities because of their transient nature and small size. Here, we obtained evidence that transient membrane heterogeneities can be frozen at cryogenic temperatures which allows the application of solid-state experimental techniques sensitive to the nanoscale distance range.

Heterogeneities in Cholesterol-Containing Model Membranes Observed by Pulsed Electron Paramagnetic Resonance of Spin Labels.

Biological membranes are supposed to have heterogeneous structure containing lipid rafts-lateral micro- and nanodomains enriched in cholesterol (chol) and sphingolipids. In this work, lipid bilayers containing a small amount of the spin-labeled chol analogue 3β-doxyl-5α-cholestane (chlstn) were studied using electron spin echo (ESE) spectroscopy, which is a pulsed version of electron paramagnetic resonance (EPR). Bilayers were prepared from an equimolecular mixture of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) with chol added at different concentrations.

Communication: Orientational self-ordering of spin-labeled cholesterol analogs in lipid bilayers in diluted conditions.

Lipid-cholesterol interactions are responsible for different properties of biological membranes including those determining formation in the membrane of spatial inhomogeneities (lipid rafts). To get new information on these interactions, electron spin echo (ESE) spectroscopy, which is a pulsed version of electron paramagnetic resonance (EPR), was applied to study 3β-doxyl-5α-cholestane (DCh), a spin-labeled analog of cholesterol, in phospholipid bilayer consisted of equimolecular mixture of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine and 1,2-dioleoyl-sn-glycero-3-phosphocholine. DCh concentration in the bilayer was between 0.