Cholesterol induces specific spatial and orientational order in cholesterol/phospholipid membranes

Area of Science:

• Membrane biophysics
• Molecular dynamics simulations
• Lipid-cholesterol interactions

Background:

• Cholesterol is crucial for ordered lipid phases and lipid rafts in cell membranes.
• The atomic-level mechanisms of cholesterol's ordering and packing capabilities are not fully understood.

Purpose of the Study:

• To elucidate the atomic-scale mechanisms behind cholesterol's ordering and packing in lipid bilayers.
• To differentiate cholesterol's membrane ordering properties from other sterols.

Main Methods:

• Atomic-scale molecular dynamics simulations were employed.
• Analysis focused on cholesterol molecule positioning and arrangement within lipid bilayers.

Main Results:

• Cholesterol molecules form a three-fold symmetric arrangement, avoiding direct contacts.
• This specific arrangement is attributed to cholesterol's unique molecular structure, particularly off-plane methyl groups.
• Other sterols with less asymmetry exhibit a significantly reduced three-fold arrangement.

Conclusions:

• Cholesterol molecules exhibit collective self-organization in lipid membranes, essential for the liquid-ordered phase.
• The emergence of the liquid-ordered phase requires specific molecular features, explaining differential sterol effects.
• The three-fold symmetry is key to identifying raft-promoting sterols.