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Effects of Ionic Liquids on the Nanoscopic Dynamics and Phase Behaviour of a Phosphatidylcholine Membrane


Ionic liquids (ILs) are potential candidates for new antimicrobials due to their tunable antibacterial and antifungal properties that are required to keep pace with the growing challenge of bacterial resistance. To a great extent their antimicrobial actions are related to the interactions of ILs with cell membrane. Here, we report effects of ILs on the dynamics and phase behaviour of the membrane of dimyristoylphosphatidylcholine (DMPC), a model cell membrane, as studied using neutron scattering techniques. Two prototypical imidazolium-based ILs 1-butyl-3-methylimidazolium tetrafluoroborate (BMIM[BF4]) and 1-decyl-3-methylimidazolium tetrafluoroborate (DMIM [BF4]) which differs only in terms of the alkyl chain length of cation, have been used for the present study. Fixed Elastic Window Scan (FEWS) shows that incorporation of ILs affects the phase behaviour of the phospholipid membrane significantly and the transition from solid gel to fluid phase shifts to lower temperature. This is found to be consistent with our differential scanning calorimetry measurements. The pressure-area isotherms of DMPC monolayer measured at air-water interface show that in the presence of ILs, isotherms shift towards the higher area-per lipid molecules. Quasielastic neutron scattering (QENS) data shows that both ILs act as a plasticizer, which enhances the fluidity of the membrane. DMIM[BF4] which has longer alkyl chain cation, affects phase behaviour and dynamics more strongly in comparison to BMIM[BF4]. Incorporation of DMIM[BF4] enhances not only the long range lateral motion but also the localised internal motion of the lipids. On the other hand, BMIM[BF4] mainly alters the localised internal motion of the lipid. Any subtle change in the dynamical properties of the membrane can profoundly affect the stability of the cell. Hence, the dominant effect of the IL with longer chain length on the dynamics of the phospholipid membrane might be correlated with their cytotoxic activity.

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Publication details

The article was received on 07 Sep 2017, accepted on 07 Nov 2017 and first published on 07 Nov 2017

Article type: Paper
DOI: 10.1039/C7SM01799E
Citation: Soft Matter, 2017, Accepted Manuscript
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    Effects of Ionic Liquids on the Nanoscopic Dynamics and Phase Behaviour of a Phosphatidylcholine Membrane

    V. Sharma, S. K. Ghosh, P. Mandal, T. Yamada, K. Shibata, S. Mitra and R. Mukhopadhyay, Soft Matter, 2017, Accepted Manuscript , DOI: 10.1039/C7SM01799E

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