Is the tilt of the lipid head group correlated with the number of intermolecular interactions at the bilayer interface?

Abstract

Lipid and water molecules comprising the bilayer form an integral entity owing to only weak physical interactions. At the bilayer interface, these interactions chiefly involve hydrogen bonding and charge pairing. Lipid head groups make hydrogen bonds (H-bonds) predominantly with water, whereas interlipid H-bonds and charge pairs are less numerous. Both interlipid H-bonding and charge pairing depend on the distance and relative orientation of the interacting head groups. In this computational paper, correlations are analysed between the orientation of the lipid head group and the number of interlipid interactions at the interface of a bilayer made of galactolipids, forming direct interlipid H-bonds, and of phosphatidylcholines forming interlipid charge pairs. The correlations are not strong, however, in both bilayers they show a similar trend.