Structural ordering of lipid bilayers induced by surfactant molecules with small hydrophilic head group

Abstract

A series of 100 ns-long molecular dynamics calculations for binary bilayers of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and 33 mol% ethylene-glycol-ethers () were performed under the isothermal–isobaric condition ( K and  atm) to investigate systematically changes in physico-chemical properties of the binary bilayer depending on the length of the hydrophilic head group and the hydrophobic tail. Remarkable differences were observed in membrane properties between the bilayers mixed with surfactants with a large hydrophilic head group and a small hydrophilic head group. In the former, the binary bilayers extended laterally with more disorder in lateral arrangement of the lipid molecules and more disordered acyl tail conformation of the DMPC molecules in the binary bilayers than those in pure DMPC bilayer. In the latter, the bilayers shrunk laterally with more order in lateral arrangement of the lipids and more ordered DMPC acyl tail conformation. The molecular mechanism of these changes in membrane properties is discussed on the basis of two-dimensional radial distribution functions of the lipid mass centres, radius of gyration of lipids and void distribution in membranes. The umbrella effect of phosphocholine head groups was investigated.

Keywords:

• Molecular dynamics calculation
• lipid bilayer
• DMPC
• ethylene-glycol-ethers
• membrane ordering

Acknowledgements

This research used the computational resources of K computer at RIKEN Advanced Institute for Computational Science (AICS) (Proposal number: hp160225). Calculations were mainly performed at the Information Technology Center of Nagoya University, partially at the Institute for Solid State Physics, the University of Tokyo, and partially at the Research Center for Computational Science, Okazaki, Japan.

Notes

No potential conflict of interest was reported by the authors.

Supplemental data for this article can be accessed here. [https://doi.org/10.1080/08927022.2017.1319061]

Additional information

Funding

This work is supported by the FLAGSHIP2020, MEXT within the priority study5 (Development of new fundamental technologies for high-efficiency energy creation, conversion/storage and use). This work was partially supported by the ‘Joint Usage/Research Center for Interdisciplinary Large-scale Information Infrastructures’ in Japan. This work is also supported by JSPS KAKENHI [grant number 16K21094] (Y.A.).