Effect of Desmosterol, Lathosterol and Coprostanol on the phase behaviour of phospholipid membranes

Sterols have played an important role in membrane evolution. The effect of these molecules, particularly the naturally occurring ones, such as cholesterol, ergosterol, lanosterol, phytosterols and oxysterols on the properties of lipid model membranes have been extensively investigated. Unfortunately, other naturally occurring sterols such as desmosterol and lathosterol have received very little attention. Using small angle X-ray scattering (SAXS), we have carried out detailed investigations on the influence of desmosterol and lathosterol along with coprostanol on the phase behaviour of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) membranes. SAXS results indicate both that these sterols modulate the properties of the DPPC bilayer in a manner similar to cholesterol. However, we have found desmosterol to be more efficient than cholesterol in suppressing the main transition of DPPC, with the fluid phase stabilized at around 15 mol% (compared to around 20 mol% in cholesterol). Coprostanol on the other hand was found to be less efficient in stabilizing the fluid phase than the other two. The results obtained from our study in combination with those existing in the literature will help in establishing a complete picture of how different sterols influence the properties of lipid membranes.