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Formation of Inverse Topology Lyotropic Phases in Dioleoylphosphatidylcholine/Oleic Acid and Dioleoylphosphatidylethanolamine/Oleic Acid Binary Mixtures

Gillams, Richard J.; Nylander, Tommy LU ; Plivelic, Tomás LU ; Dymond, Markus K. and Attard, George S. (2014) In Langmuir 30(12). p.3337-3344
Abstract
The addition of saturated fatty acids (FA) to

phosphatidylcholine lipids (PC) that have saturated acyl chains

has been shown to promote the formation of lyotropic liquidcrystalline

phases with negative mean curvature. PC/FA

mixtures may exhibit inverse bicontinuous cubic phases

(Im3m, Pn3m) or inverse topology hexagonal phases (HII),

depending on the length of the acyl chains/fatty acid. Here we

report a detailed study of the phase behavior of binary

mixtures of dioleoylphosphatidylcholine (DOPC)/oleic acid

(OA) and dioleoylphosphatidylethanolamine (DOPE)/oleic

acid at limiting hydration, constructed using small-angle X-ray

diffraction (SAXD)... (More)
The addition of saturated fatty acids (FA) to

phosphatidylcholine lipids (PC) that have saturated acyl chains

has been shown to promote the formation of lyotropic liquidcrystalline

phases with negative mean curvature. PC/FA

mixtures may exhibit inverse bicontinuous cubic phases

(Im3m, Pn3m) or inverse topology hexagonal phases (HII),

depending on the length of the acyl chains/fatty acid. Here we

report a detailed study of the phase behavior of binary

mixtures of dioleoylphosphatidylcholine (DOPC)/oleic acid

(OA) and dioleoylphosphatidylethanolamine (DOPE)/oleic

acid at limiting hydration, constructed using small-angle X-ray

diffraction (SAXD) data. The phase diagrams of both systems

show a succession of phases with increasing negative mean

curvature with increasing OA content. At high OA concentrations, we have observed the occurrence of an inverse micellar Fd3m

phase in both systems. Hitherto, this phase had not been reported for phosphatidylethanolamine/fatty acid mixtures, and as such

it highlights an additional route through which fatty acids may increase the propensity of bilayer lipid membranes to curve. We

also propose a method that uses the temperature dependence of the lattice parameters of the HII phases to estimate the

spontaneous radii of curvature (R0) of the binary mixtures and of the component lipids. Using this method, we calculated the R0

values of the complexes comprising one phospholipid molecule and two fatty acid molecules, which have been postulated to drive

the formation of inverse phases in PL/FA mixtures. These are −1.8 nm (±0.4 nm) for DOPC(OA)2 and −1.1 nm (±0.1 nm) for

DOPE(OA)2. R0 values estimated in this way allow the quantification of the contribution that different lipid species make to

membrane curvature elastic properties and hence of their effect on the function of membrane-bound proteins. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Langmuir
volume
30
issue
12
pages
3337 - 3344
publisher
The American Chemical Society
external identifiers
  • scopus:84897498067
ISSN
0743-7463
DOI
10.1021/la404275u
language
English
LU publication?
yes
id
3187b261-3f2a-43f7-93f8-e54100e5e57c (old id 4905283)
date added to LUP
2015-01-05 16:45:59
date last changed
2017-11-19 03:05:31
@article{3187b261-3f2a-43f7-93f8-e54100e5e57c,
  abstract     = {The addition of saturated fatty acids (FA) to<br/><br>
phosphatidylcholine lipids (PC) that have saturated acyl chains<br/><br>
has been shown to promote the formation of lyotropic liquidcrystalline<br/><br>
phases with negative mean curvature. PC/FA<br/><br>
mixtures may exhibit inverse bicontinuous cubic phases<br/><br>
(Im3m, Pn3m) or inverse topology hexagonal phases (HII),<br/><br>
depending on the length of the acyl chains/fatty acid. Here we<br/><br>
report a detailed study of the phase behavior of binary<br/><br>
mixtures of dioleoylphosphatidylcholine (DOPC)/oleic acid<br/><br>
(OA) and dioleoylphosphatidylethanolamine (DOPE)/oleic<br/><br>
acid at limiting hydration, constructed using small-angle X-ray<br/><br>
diffraction (SAXD) data. The phase diagrams of both systems<br/><br>
show a succession of phases with increasing negative mean<br/><br>
curvature with increasing OA content. At high OA concentrations, we have observed the occurrence of an inverse micellar Fd3m<br/><br>
phase in both systems. Hitherto, this phase had not been reported for phosphatidylethanolamine/fatty acid mixtures, and as such<br/><br>
it highlights an additional route through which fatty acids may increase the propensity of bilayer lipid membranes to curve. We<br/><br>
also propose a method that uses the temperature dependence of the lattice parameters of the HII phases to estimate the<br/><br>
spontaneous radii of curvature (R0) of the binary mixtures and of the component lipids. Using this method, we calculated the R0<br/><br>
values of the complexes comprising one phospholipid molecule and two fatty acid molecules, which have been postulated to drive<br/><br>
the formation of inverse phases in PL/FA mixtures. These are −1.8 nm (±0.4 nm) for DOPC(OA)2 and −1.1 nm (±0.1 nm) for<br/><br>
DOPE(OA)2. R0 values estimated in this way allow the quantification of the contribution that different lipid species make to<br/><br>
membrane curvature elastic properties and hence of their effect on the function of membrane-bound proteins.},
  author       = {Gillams, Richard J. and Nylander, Tommy and Plivelic, Tomás and Dymond, Markus K. and Attard, George S.},
  issn         = {0743-7463},
  language     = {eng},
  number       = {12},
  pages        = {3337--3344},
  publisher    = {The American Chemical Society},
  series       = {Langmuir},
  title        = {Formation of Inverse Topology Lyotropic Phases in Dioleoylphosphatidylcholine/Oleic Acid and Dioleoylphosphatidylethanolamine/Oleic Acid Binary Mixtures},
  url          = {http://dx.doi.org/10.1021/la404275u},
  volume       = {30},
  year         = {2014},
}