Molecular aspects of the interaction between plants sterols and DPPC bilayers: An experimental and theoretical approach

The effect of sterols composition in a lipid bilayer was investigated on membranes of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and mixtures with the plant sterols β-sitosterol and stigmasterol. Differential scanning calorimetry, 1,6-diphenyl-1,3,5-hexatriene (DPH) fluorescence polarization and infrared spectroscopy studies showed that both sterols changed the packing of the membrane and the hydration of the polar headgroup of the phospholipids, disordering the gel phase and, vice versa, ordering the membrane in the liquid crystalline phase. In all cases some differences among β-sitosterol and stigmasterol could be observed, being β-sitosterol slightly more efficient than stigmasterol in ordering a fluid membrane, bringing the membrane to a more packed liquid ordered phase. Molecular dynamic simulations were carried out to better characterize the distinct behavior of both sterols in a DPPC-membrane. The calculated parameters agreed quite well with the experimental results and a molecular model is proposed to explain differences in the sterols molecules and their effect on the DPPC-bilayer.

Molecular conformers of DPPC predicted in the presence of plant sterols. In gray it is shown the tilting effect caused in a DPPC molecule by the inclusion of sitosterol or stigmasterol in a DPPC membrane.Figure optionsDownload high-quality image (80 K)Download as PowerPoint slideResearch highlights
► We have studied the differential effects between sitosterol and stigmasterol on a DPPC membrane.
► Sitosterol results to be more efficient in ordering a fluid DPPC membrane than stigmasterol.
► Molecular dynamics studies are carried out to understand the effect of both sterols.
► A molecular model is proposed to explain sterol-DPPC interactions and membrane structure.