Unwin, Nigel. "Refined Structurerapid of thesolvent nAChRexchange." at

Unwin, Nigel. "Refined Structurerapid of thesolvent nAChRexchange." at

Unwin,
Nigel. "Refined
Structurerapid
of thesolvent
nAChRexchange."
at 4 resolution."
JMB, 2004: 967-989.
Buboltz, Jeffrey T, and Gerald W Feigenson. "A novel strategy for
the preparation
of liposomes:
BBA-Biomembranes,
1999: 232-245.
Unwin,
Nigel.
"Refined
Structure
of
the
nAChR
at
4

resolution."
JMB,
2004:
967-989.
Buboltz,
Jeffrey
T,
and
Gerald
W
Feigenson.
"A
novel
strategy
for
the
preparation
of
liposomes:
rapid
solvent
exchange."
BBA-Biomembranes,
1999:
232-245.
Hassan-Zadeh, E, F Hussain, and J Huang. "Gramicidin Peptides Alter Global Lipid Compositions and Bilayer Thicknesses of Coexisting Liquid-Ordered
and
Liquid-Disordered Membrane Domains." Langmuir, 2017: 3324-3332.
Hassan-Zadeh,
E, F Hussain,
and
Huang.
"Gramicidin
Peptides JMB,
Alter 2004:
Global967-989.
Lipid Compositions and Bilayer Thicknesses of Coexisting Liquid-Ordered and Liquid-Disordered Membrane Domains." Langmuir, 2017: 3324-3332.
Unwin,
Nigel. "Refined
Structure
of Jthe
nAChR
at 4 resolution."
Unwin,
Nigel.
Structure
of the nAChR
at 4 resolution."
JMB, 2004:
Zhao,
Jiang,
et al."Refined
"Phase studies
of model
biomembranes:
Complex behavior
of 967-989.
DSPC/DOPC/Cholesterol." BBA-Biomembranes, 2007: 2764-2776.
Zhao, Jiang, et al. "Phase studies of model biomembranes: Complex behavior of DSPC/DOPC/Cholesterol." BBA-Biomembranes, 2007: 2764-2776.

Alteration of membrane domain compositions by Protein
nAChRs
Jigesh Patel, Robert Fisher, Dr. Juyang Huang
Abstract

A

B

In this study, the effects of adding membrane protein nAChRs to
DOPC/DSPC/cholesterol lipid bilayers containing coexisting phases are
investigated. This work is the first study of its kind that investigates the
effect of ion-transmitter nAChRs on Lo+Ld phase boundaries. The
modification of phase boundary by nAChRs is determined using
fluorescence microscopy on Giant Unilamellar Vesicles (GUVs). After
phase boundaries are determined, thermodynamic tie-lines and
protein's partition coefficients will be measured. Those data will allow
us to precisely determine the exact concentrations of nAChRs in
various cell membrane domains. Accurate measurement of the
perturbations of the phase boundaries by the protein could serve as an
important means to quantitatively understand the universal behavior of
a range of membrane proteins.

Determining the Phase Boundary of Lo + Ld
Coexisting Region

nAChRs
The nicotinic ACh receptor (Fig. 3) is fairly large channel protein
consisting of 2200 amino acids, weighs approximately 290 kDa and
spans ~160 across the cell membrane. It is mainly found at the
nerve-muscle synapse, where it mediates fast chemical transmission of
electrical signal in response to ACh released into the synaptic cleft.

Figure 2 A) Damp-film method B) Electroformation of GUVs

The liposomes were produced using the RSE procedure (Fig. 1). The
GUVs were then prepared using the damp-film method (Fig. 2A)
followed by electroformation (Fig 2B). Fluorescence images and videos
of GUVs were captured using CCD camera on an inverted microscope
with a 40 objective. All images and videos were captured at 25 C.
The mole fraction of nAChR in all samples was fixed. The overall lipid
composition of a sample is specified by two parameters: the R value [R
= DSPC/(DSPC + DOPC)] and cholesterol mole fraction C. In order to
simplify the comparison of results with and without nAChR, the protein
is not included in lipid composition calculation.

Figure 3 Nicotinic acetylcholine receptors (nAChRs)

Conclusion
In DOPC/DSPC/Cholesterol ternary mixtures containing coexisting
Lo+Ld phases, nAChRs alters the phase boundary and thermodynamic
tie-lines. Our study shows that trans-membrane proteins play a
significant role in the controlling of the lipid composition of membrane
domains. Membrane domain size, composition, order, and protein
partition behavior are important to biomembrane function, membrane
protein activity, disease development and diagnosis, and drug design.
Our studies advances our knowledge about fundamental protein-lipid
interactions.

A

References:
Buboltz, Jeffrey T, and Gerald W Feigenson. "A novel strategy for the
preparation of liposomes: rapid solvent exchange." BBABiomembranes, 1999: 232-245.
Hassan-Zadeh, E, F Hussain, and J Huang. "Gramicidin Peptides Alter
Global Lipid Compositions and Bilayer Thicknesses of Coexisting
Liquid-Ordered and Liquid-Disordered Membrane Domains." Langmuir,
2017: 3324-3332.
Unwin, Nigel. "Refined Structure of the nAChR at 4 resolution." JMB,
2004: 967-989.
Zhao, Jiang, et al. "Phase studies of model biomembranes: Complex
behavior of DSPC/DOPC/Cholesterol." BBA-Biomembranes, 2007:
2764-2776.

Figure 1 RSE apparatus and cross-sectional schematic

Figure 4 Ternary phase diagrams of DOPC/DSPC/Cholesterol with nAChRs (the dashed line) and
without the protein (the solid line). Blue dots: GUVs having coexisting Lo+Ld phases; red dots: GUVs
having only one phase.

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