Effect of Bio-compatible Ionic Liquid-Choline Glycinate on the Structure of Lipid Membranes

Pratibha Kumari and Hemant K. Kashyap

Department of Chemistry, IIT Delhi, Delhi, India.

 

Choline amino acid ionic liquids (ChAAILs) are considered as highly bio-degradable and bio-compatible solvents and have been attracted scientific community to explore their uses in various industrial applications. The toxicological scrutening and environmental fate analysis of these ILs are requisite to employ these IL solvents on large scale. In the present work, we have investigated how the presence of simplest form of ChAAILs, choline glycinate (ChGly), affects the structure and stability of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylethanolamine (POPE) lipid bilayer via molecular dynamics simulation. The study reveals a considerable compression of POPC bilayer along with an enhanced ordering of hydrocarbon lipid tails on increasing the concentration of ChGly IL. On the other hand, the stability and structure of the POPE bilayer is hardly affected at lower concentration of ChGly, but at higher concentration (20 mol %) the structure of the bilayer is slightly changed. The H-bond analysis reveal that choline cations have similar propensity to H-bond with phosphate and carbonyl oxygens of POPC and POPE lipid molecules whereas the glycinate anions have more tendency to H-bond to POPE lipid molecules due to the presence of H-bond donor ammonium group. However, the structural properties of POPE bilayer are influenced by ChGly IL to lesser extent compared to POPC bilayer which is a direct consequence of the ability of POPE lipid to form strong inter- as well as intra-molecular H-bonding network and adopting a more compact packed bilayer structure.

References:

1.Liu, Q.-P.; Hou, X.-D.; Li, N.; Zong, M.-H. Ionic liquids from renewable biomaterials:synthesis, characterization and application in the pretreatment of biomass.Green Chem. 2012, 14, 304-307
2.Yoo, B.; K., S. J.; Yingxi, Z.; J., M. E. Amphiphilic interactions of ionic liquids with lipid biomembranes: a molecular simulation study. Soft Matter 2014, 10, 8641-8651
3.Clarke, C. J.; Tu, W.-C.; Levers, O.; Brohl, A.; Hallett, J. P. Green and Sustainable Solvents in Chemical Processes. Chem. Rev. 2018, 118, 747-800