Common anesthetic molecules prefer to partition in liquid disorder phase domain in a composite multicomponent membrane

Abstract

Despite a vast clinical application of anesthetics, the molecular level of understanding of general anesthesia is far from our reach. Using atomistic molecular dynamics simulation, we study the effects of common anesthetics: ethanol, chloroform and methanol in the fully hydrated symmetric multicomponent lipid bilayer membrane comprising of an unsaturated palmitoyl-oleoyl-phosphatidyl-choline (POPC), a saturated palmitoyl-sphingomyelin (PSM) and cholesterol (Chol) which exhibits phase coexistence of liquid-ordered (lo) - liquid disordered (ld) phase domains. We find that the mechanical and physical properties such as the thickness and rigidity of the membrane are reduced while the lateral expansion of the membrane is exhibited in presence of anesthetic molecules. Our simulation shows both lateral and transverse heterogeneity of the anesthetics in the composite multicomponent lipid membrane. Both ethanol and chloroform partition in the POPC-rich ld phase domain, while methanol is distributed in both lo-ld phase domains. Chloroform can penetrate deep into the membrane, while methanol partitions mostly at the water layer closed to the head-group and ethanol at the neck of the lipids in the membrane.