Abstract
The effect of lipid composition on models of the inner leaflet of mammalian cell membranes has been investigated. Grazing incidence X-ray diffraction and X-ray and neutron reflectivity have been used to characterize lipid packing and solvation, while electrochemical and infrared spectroscopic methods have been employed to probe phase behavior in an applied electric field. Introducing a small quantity of the anionic lipid dimyristoylphosphatidylserine (DMPS) into bilayers of zwitterionic dimyristoylphosphatidylethanolamine (DMPE) results in a significant change in the bilayer response to an applied field: the tilt of the hydrocarbon chains increases before returning to the original tilt angle on detachment of the bilayer. Equimolar mixtures, with slightly closer chain packing, exhibit a similar but weaker response. The latter also tend to incorporate more solvent during this electrochemical phase transition, at levels similar to those of pure DMPS. Reflectivity measurements reveal greater solvation of lipid layers for DMPS > 30 mol %, matching the greater propensity for DMPS-rich bilayers to incorporate water. Taken together, the data indicate that the range of 10-35 mol % DMPS provides optimum bilayer properties (in flexibility and function as a barrier), which may explain why the DMPS content of cell membranes tends to be found within this range.
Original language | English |
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Journal | Langmuir |
DOIs | |
State | Accepted/In press - 2022 |
Externally published | Yes |
Funding
A.L.M., P.N.J., and T.H. are grateful to the BBSRC-funded Midlands Integrative Biosciences Training Partnerships (BB/M01116X/1, BB/J014532/1, and BB/T00746X/1, respectively) and to the University of Birmingham for studentships. A.W.B. thanks the University of Birmingham for a studentship. The electrochemical and infrared measurements were funded by an EPSRC project (EP/D05561X/1) and a Royal Society Small Equipment Grant. This work was carried out with the support of Diamond Light Source (experiments SI-14670, SI-16423), the Birmingham-Diamond Collaboration (experiment SI-19542), and ISIS Neutron and Muon Source (experiment RB1620500). Neutron reflectivity data are openly available from ISIS at 10.5286/ISIS.E.RB1620500 . Other data supporting this publication are openly available from the UBIRA eData repository at 10.25500/edata.bham.00000866 .