The comparison of zymosterol vs cholesterol membrane properties –The effect of zymosterol on lipid monolayers

In this work systematic investigations on the influence of zymosterol (zymo), which is one of cholesterol precursors, on lipid monolayers were done. The aim of these studies was to perform thorough comparison of zymosterol vs cholesterol membrane activity and fill the gap in the studies on the effect of sterols on membranes. The Langmuir monolayers experiments combined with Brewster angle microscopy studies were performed on binary (SM:zymo, POPC:zymo, GM3:zymo) and ternary (SM:POPC:zymo, SM:GM3:zymo) films differing in the sterol content. The obtained results evidenced differences in the influence of both sterols on lipid monolayers, which was manifested in the parameters calculated based on the isotherms as well is in monolayers morphology. It was found that zymosterol is of condensing, ordering and domain promoting abilities thus this molecule can be included to the group of membrane active sterols. However, zymosterol is much less effective than cholesterol as condensing and ordering agent. These findings were attributed to the differences in the structure of both sterols and their ability to pack tightly with other lipids in the mixed systems.