Stabilization of DPPC lipid bilayers in the presence of co-solutes: molecular mechanisms and interaction patterns

We study the interactions between dipalmitoylphosphatidylcholine (DPPC) lipid bilayers in the gel and the fluid phase with ectoine, amino ectoine and water molecules by means of atomistic molecular dynamics (MD) simulations and conceptual density functional theory (DFT) calculations. Our results reveal a pronounced preferential exclusion of both co-solutes from the DPPC lipid bilayer which is stronger for the fluid phase. The corresponding outcomes can be brought into relation with the Kirkwood-Buff theory of solutions in order to provide a thermodynamic rationale for the experimentally observed stabilization of the gel phase. Closely related to preferential exclusion of both co-solutes, our simulations also highlight a preferential hydration behavior as manifested by an increased number of hydrogen bonds between water and DPPC molecules. All results are rationalized by conceptual DFT calculations with regard to differences in the electronic properties between ectoine and amino ectoine.

Automated summary

The study used MD simulations and DFT calculations to investigate the interactions between DPPC lipid bilayers and ectoine, amino ectoine, and water molecules. The results showed a pronounced preferential exclusion of the co-solutes from the lipid bilayers, with stronger exclusion in the fluid phase. The simulations also revealed a preferential hydration behavior with increased hydrogen bonds between water and DPPC molecules, which could be rationalized by differences in electronic properties between ectoine and amino ectoine.