Hybrid coarse-grained and all-atom molecular dynamics simulation studies of binary biological lipid membranes containing chlorosulfolipids

Chlorosulfolipids are the main component of the polar lipid of the flagellar membrane in sea algae and are also known as the major cause of seafood poisoning. Despite the active research on the synthesis of these chlorosulfolipids as potential new drugs, there has been no clear understanding of how they are organized into a stable biological membrane, which is mainly due to their peculiar structure containing hydrophilic sulfate and chloro groups in their tail region. In this study, we have performed hybrid coarse-grained and all-atom molecular dynamics simulations to understand the structural, dynamical, and thermodynamical properties of binary mixture membrane systems consisting of Danicalipin A (DANI), one of the representative chlorosulfolipids, and 1,2-dipalmitoyl-sn-glycero-3-O-4'-(N,N,N-trimethyl)-homoserine (DPTS) lipids. We have observed that at low DANI concentration, DANI is intercalated into one of the leaflets of DPTS bilayer membranes with a y-shaped conformation, consistent with previous experiments. On the other hand, at high DANI concentration, DANI forms a stable monolayer membrane as predicted by our previous simulation study. In the intermediate DANI concentrations, however, DANI molecules tend to reside near the bilayer membrane center to facilitate water penetration through the membrane, affecting the stability of the biological membrane. In addition, there exists a gel-to-liquid crystalline transition in the DANI concentration between 30% and 40%, which was confirmed by both structural and dynamical properties such as the membrane volume, pair distribution function, and diffusion coefficients. We have also investigated the effects of temperature on the phase behavior of the mixture membrane system and found little sensitivity in the range of T = 273-323 K.