Interaction of hydroxy-xanthones with phosphatidylcholines: The effector decreases compressibility and increases the fluidity of membranes

Abstract

This work reports the effect of hydroxy-xanthones (XAs) on 1,2-Dipalmitoyl-sn-glycero-3-phosphocholine(DPPC) and 1,2-Dimyristoyl-sn-glycero-3-phosphocholine (DMPC) bilayers as determined by ultrasound velocimetry,densimetry and molecular dynamics simulations. XAs with different number of hydroxyl group werestudied. Experimental results, in good agreement with molecular dynamics simulations, revealed that the presenceof XAs in the systems studied increases fluidity while simultaneously decreses the compressibility of bothmembranes. This ´apparent contradiction´ ceases to exist when the particular geometrical structure of thexanthones is taken into account: the planar shape of their fused aromatic rings might allow them to pack efficientlyamong the hydrocarbon tails of the lipids, thus decreasing compressibility, while their presence weakensor disrupts methylene-methylene interchain interactions, thus increasing membrane fluidity and decreasing theirmelting temperature.