RELEASE OF CONTENT
THROUGH MECHANOSENSITIVE GATES IN
PRESSURISED LIPOSOMES
Martti Louhivuori
University of Groningen

M. Louhivuori / ISSP workshop / Tokyo, 24.8.2010

www.cgmartini.nl

MARTINIcoarse-grained model

M. Louhivuori / ISSP workshop / Tokyo, 24.8.2010

DPPC
Qo

water

cholesterol

Qa

SP1

peptide !ALYWK"
C1C5SC3Na

P4

SP1
SNdbutane

SC1SC4C1

Qd

C1
SC4C3

SC4MARTINI CG modelinteraction sites
M. Louhivuori / ISSP workshop / Tokyo, 24.8.2010Noparametrisation of MARTINI
experimental !thermodynamic" data! non#bonded interactions
atomistic MD simulations! bonded interactions

M. Louhivuori / ISSP workshop / Tokyo, 24.8.2010

distribution

angle

parametrisation
bonded interactions
M. Louhivuori / ISSP workshop / Tokyo, 24.8.2010

parametrisation
non#bonded interactions
M. Louhivuori / ISSP workshop / Tokyo, 24.8.2010

THE VALIDATION

comparing to experimental measurements

Rhombohedral phase (experimentally observed for DOPC/DOPE 3:1 and 2:1 Lyan & Huang, 2002)

side view

top view

Reproduced in CG simulation (Marrink & Mark, Biophys. J., 2004)
M. Louhivuori / ISSP workshop / Tokyo, 24.8.2010

bilayers

rafts

vesiclesvesicles w/ proteinssugarsmembrane proteins

M. Louhivuori / ISSP workshop / Tokyo, 24.8.2010

bilayers

rafts

vesiclesvesicles w/ proteinssugarsmembrane proteins

M. Louhivuori / ISSP workshop / Tokyo, 24.8.2010

DPPC

SPEED
Qa
water
short#range interactions
large time#step
few degrees
offreedom
NaQo

P4

butanecholesterol

peptide !ALYWK"

GENERAL
SP1
consistent C1
modeling
biomolecular systems
SP1
SC3 easily extended

C5

SNd
SC1

EASE of USE
C1
building#block approach
limited # of particles
SC4 physical units

SC4ACCURACY
parametrisation based on
C1
SC4Qd
thermodynamic data
C3
multi#level optimisation No

MARTINI CG modelinteraction sites
M. Louhivuori / ISSP workshop / Tokyo, 24.8.2010

mmm!
ouch!

drugs

patient

targeted drug release.
how?
M. Louhivuori / ISSP workshop / Tokyo, 24.8.2010

drug delivery vehicle“nanobot”

BOOM

M. Louhivuori / ISSP workshop / Tokyo, 24.8.2010

drug delivery vehicle“nanobot”

M. Louhivuori / ISSP workshop / Tokyo, 24.8.2010

mechano-sensitive channels“safety valves” of cell
sense tension in themembrane
MscL, MscK, MscS,MscM< 10 mN/m
PDB: 2VV5

M. Louhivuori / ISSP workshop / Tokyo, 24.8.2010

topbottom

MscL
controllable activation & non!selective conductance
M. Louhivuori / ISSP workshop / Tokyo, 24.8.2010

MscL activity
flickering conductivity
multiple levels! subconductive states
activation < 1 ms
de#activation 1$100 ms

Sukharev et al. !1997"
Annu Rev Physiol 59: 633$657

M. Louhivuori / ISSP workshop / Tokyo, 24.8.2010

non-selective channel
no ion selectivity
even smallproteins passthrough! 15$20 Å

Cruickshank et al. !1997"
Biophys J 73: 1925$1931
M. Louhivuori / ISSP workshop / Tokyo, 24.8.2010

photosensitivivity
attached
compoundundergoes light
induced charge
separation
reversible
localised

Koçer et al. !2005"
Science 309: 755$758

M. Louhivuori / ISSP workshop / Tokyo, 24.8.2010

photosensitivivity
photosensitive lipids
used to transfer signal
to mechanical stressreversible
localised

Folgering et al. !2004"
Langmuir 20: 6985$6987
M. Louhivuori / ISSP workshop / Tokyo, 24.8.2010

nano-container

nano-particlesaka liposome

aka drugs

M. Louhivuori / ISSP workshop / Tokyo, 24.8.2010

nano-transporter
liposomes
tiny lipid vesicles
membrane fusiontrans#membrane transport
drug delivery
curvature e%ects

MscL
mechano#sensitive
pressure valves of cells
touch & hearnon#selective, large
membrane channel
M. Louhivuori / ISSP workshop / Tokyo, 24.8.2010

game plan

BOOM

M. Louhivuori / ISSP workshop / Tokyo, 24.8.2010

MscL saves the day
M. Louhivuori / ISSP workshop / Tokyo, 24.8.2010

660 kN/m·s ! lysis
140 kN/m·s ! okoh-oh!

M. Louhivuori / ISSP workshop / Tokyo, 24.8.2010

analysis

M. Louhivuori / ISSP workshop / Tokyo, 24.8.2010

analysis
closedopen

M. Louhivuori / ISSP workshop / Tokyo, 24.8.2010

5 us

activation
mechanism

M. Louhivuori / ISSP workshop / Tokyo, 24.8.2010

postactivation
67 mN/m" 24 nm1.04 H2O / ns

M. Louhivuori / ISSP workshop / Tokyo, 24.8.2010

140

equilibrium?

tension (mN/m) / pressure (bar)120

tensionpressure100

8060(-1.12 ± 0.05) bar/µs
40(93 ± 4) µs

20(86 ± 4) µs(-0.54 ± 0.02) mN/µs
m00102030

405060time (µs)
M. Louhivuori / ISSP workshop / Tokyo, 24.8.2010708090MFFA
boundary
potentials

3.5RDF

32.5

21.5

10.5

0012

3r [nm]456

mimic interactions withbulk solvent
30

MFFA

20

100

-10

-20

Risselada et al. !2008"-30
23J Phys Chem B 112: 7438$7447
M. Louhivuori / ISSP workshop / Tokyo, 24.8.2010

4r [nm]56

pumping water into
liposomes
additional mean#fieldpotential inside theliposome
start with r = 0.01 nmincrease slowly for 20nsuntil r = 3.9 nm
fill the cavity withwater, relax and repeat
as needed
M. Louhivuori / ISSP workshop / Tokyo, 24.8.2010

water-repellant lipid tails
modified Lennard#
Jones potential against
waterepsilon
sigma
V (r) = 4!

C5
2.00.47!" #σ 12r

wC5
2.00.7−" σ #6 $r

DOPCwDOPC

NC3

NC3

PO4

PO4

GL1

GL1
GL2

C1

GL2
C1

C1
C2

C1
C2

C2
D3

C2
D3

D3C4

D3C4C4C5C4wC5C5C5M. Louhivuori / ISSP workshop / Tokyo, 24.8.2010

wC5C5

3D pressure fields
Ollila et al. !2009"
Phys Rev Lett, 102: 078101

divide system into a 3D
grid
use local virial for eachvolume element
calculate averages


$1 #
1#
Plocal (r) =δ (r − ri ) mi vi ⊗ vi +Fij
δ(r − 1)dl
V2
Ci ji
i!=j

M. Louhivuori / ISSP workshop / Tokyo, 24.8.2010

flow rate
Partial densities
2000
Protein
wDOPC
W
PO4

R!

!

-3

Density (kg m )

1500

1000

500

00

510Box (nm)1520

M. Louhivuori / ISSP workshop / Tokyo, 24.8.2010

Rsummarylarge#scale biologicalsystems accessible to CG
simulations

water flux
OUT: !6.0 ± 1.3"& ions/ns
IN: !1.7 ± 0.3"& ions/ns

release of an osmotic
shock via MscL
activation achieved

MODEL: 0.2$40& ions/ns

MscL activation isindeed a last#ditch e%ort
to prevent lysis
iris#like, non#symmetric
opening&&Steinbacher et al. !2007"
CurrTopicsMembranes 58:1#24

pore radius !11.6 ± 0.8" Å& !exp. 15$20 Å"blocking of the channel
by the cytoplasmic
helices a first step inclosure?

M. Louhivuori / ISSP workshop / Tokyo, 24.8.2010

futuredye molecules to directlycompare our release ofnano#particles toexperimental datanano#pores formed byother molecules, e.g.
anti#microbial peptides

activation of the channel
using lyso#lipids

M. Louhivuori / ISSP workshop / Tokyo, 24.8.2010

Siewert#Jan Marrink
Erik van der Giessen
Jelger Risselada
UPPSALA UNIVERSITETDavid van der Spoel
TAMPERE UNIVERSITY OF TECHNOLOGY

Samuli Ollila
Ilpo Vattulainen
Stockholm University

Erik Lindahl
M. Louhivuori / ISSP workshop / Tokyo, 24.8.2010