Spontaneous Aggregation

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Spontaneous Aggregation of Lipids and
Surfactants
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Biological membranes
composition complex mixture of lipids and
proteins
structure fluid mosaic model
structure lipid raft
http//www.bms.ed.ac.uk/research/others/smaciver/C
yto-Topics/ lipid_rafts_and_the_cytoskeleton.htm
How do membrane composition and structure
relate to membrane function?
http//sun.menloschool.org/cweaver/cells/c/cell_m
embrane/
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Spontaneous Aggregation of Phospholipid Bilayers.

• DPPC naturally occurring phospholipid
• well studied computationally

Temp 323 K (fluid phase) 64 DPPC 3000 SPC water
dipalmitoylphosphatidylcholine (DPPC)
S.J. Marrink, E. Lindahl, O. Edholm and A.E. Mark
J. Am. Chem. Soc. 123 (2001) 8638-8639
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Random initial mixture of phospholipid and water
S.J. Marrink
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Equilibrated Bilayer
S.J. Marrink
6
Spontaneous assembly of phospholipds into a
bilayer
A
C
B
0 ns
0.2 ns
3 ns
Ceq
Deq
C
25 ns
20 ns
10 ns
S.J. Marrink
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Density Evolution
density
water
head groups
lipid tails
S.J. Marrink
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Mechanism
S.J. Marrink
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Pore Closure
S.J. Marrink
10
Rate Limiting Step Collapse of water pores
Water pore
S.J. Marrink
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Stabilize pore by application of tension
within membrane.
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DOPE 128 lipids 4566 SPC water
DOPE dioleylphosphatidylethanolamine
181c9/181c9
Experimentally DOPE adopts inverted hexagonal
phase at 300K
19 ns
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Mixed Systems
Lipids 6464 8500 SPC water
DOPC 5050 DOPE
0 ns
24 ns
DOPC dioleylphosphatidylcholine
181c9/181c9 DOPE dioleylphosphatidylethanolamine
181c9/181c9
21 ns
16 ns