Structure and Stability of Phospholipid Bilayers Hydrated by a Room-Temperature Ionic Liquid/Water Solution: a Neutron Reflectometry Study

Published

October 23, 2014

Author(s)

Antonio Benedetto, Frank Heinrich, Miguel A. Gonzalez, Giovanna Fragneto, Erik Watkins, Pietro Ballone

Abstract

Neutron reflectometry measurements (NR) have been carried out to probe the structure and stability of two model bio-membranes consisting of POPC and DMPC phospholipid bilayers hydrated by water solutions of two prototypical room-temperature ionic liquids (RTIL), i.e., 1- butyl-3-methyl-imidazolium chloride ([bmim][Cl]) and choline chloride ([Chol][Cl]) at concentration 0.1M and 0.5M. The raw data have been analysed by fitting a distribution of scattering length densities arising from the different chemical species in the system. The results of this analysis show that: (a) for all systems and concentrations that we considered, the thickness of the bilayers shrinks by 1 A upon dissolving the ionic liquid into water; (b) the RTIL ions enter the bilayer, finding their way to a preferred location in the lipid range that is nearly independent of the lipid and of the [bimim]+ or [Chol]+ choice. The volume fraction of RTIL sorbed in/on the bilayer, however, does depend on the lipid, but, again, is the same for [bmim][Cl] and for [Chol][Cl]. Thus, the RTIL occupies 5% of the bilayer volume in POPC, rising to 10% in DMPC. Repeating the measurements and data analysis after rinsing in pure water shows that the changes in the bilayer due to the RTIL sorption are irreversible, and that a measurable amount of IL remains in the lipid fraction, i.e. 2.5% of the bilayer volume in POPC, and 8% in DMPC.

Citation

Journal of Physical Chemistry B

Volume

118

Pub Type

Journals

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Keywords

neutron reflectometry, lipid bilayer, ionic liquids

Citation

Benedetto, A. , Heinrich, F. , Gonzalez, M. , Fragneto, G. , Watkins, E. and Ballone, P. (2014), Structure and Stability of Phospholipid Bilayers Hydrated by a Room-Temperature Ionic Liquid/Water Solution: a Neutron Reflectometry Study, Journal of Physical Chemistry B, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=916596 (Accessed December 26, 2024)