The magnitude of condensation induced by cholesterol on the mixtures of sphingomyelin with phosphatidylcholines—Study on ternary and quaternary systems

The studies on the condensing and ordering effect of cholesterol by application of the Langmuir monolayer technique are usually performed on binary lipid/cholesterol systems. The results concerning a quantitative analysis of these effects in multicomponent monolayers are very limited. In this work the condensing and ordering effect of cholesterol in ternary (SM/DSPC/Chol and SM/DOPC/Chol) and quaternary (SM/DSPC/DOPC/Chol) films was investigated. It was evidenced that the systems containing saturated PC (both SM/DSPC and SM/DSPC/Chol) are always more condensed and chain-ordered than the systems containing unsaturated PC (SM/DOPC and SM/DSPC/DOPC and their mixtures with cholesterol). However, the magnitude of condensation provoked by cholesterol at higher surface pressures is stronger on the monolayers containing unsaturated PC. The addition of cholesterol into SM/PC films induces the increase of chain-ordering however, the effectiveness of cholesterol as an ordering agent is determined by the presence/absence of unsaturated phospholipid. The magnitude of the effect of cholesterol on the investigated mixed monolayer was analyzed in the context of the influence of sterol on lipid chains (ordering, straightening and reorientation of chains) as well as the reorientation of polar heads.

Figure optionsDownload as PowerPoint slideResearch highlights▶ Ternary and quaternary mixtures were studied in term of the effect of cholesterol. ▶ Magnitude of condensation is stronger on SM/DOPC/Chol than on SM/DSPC/Chol films. ▶ Magnitude of condensation is also related to reorientation of lipids polar heads. ▶ The presence of unsaturated PC strongly affects ordering effectiveness of sterol.