Headgroup interactions have been suggested to have a crucial impact on the ability of certain lipids to form interdigitated structures below T m . This was explored by analyzing hydrogen bonding, hydration, and dynamics of the MMG hydrophilic region, which was considered here to consist of the glycerol moiety and the hydrophilic part of the lipid acid moiety. Hydrogen bonding analysis revealed that MMG-1 generally forms fewer intermolecular hydrogen bonds than MMG-6 (Table ). The differences are most evident in the non-interdigitated double bilayer system. These results possibly reflect the discrepancies in the headgroup interactions within the inner leaflets of the double bilayer. The hydrogen bond analysis also shows that MMG-1 is more inclined to form intramolecular bonds both in single and double bilayers.