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DNA motors
Curie Institute!
DNA replication!
DNA translocation!
Die Helikase „dröselt“ DNA auf
Bensimon, Croquette et al.
6!δz=6 bp pro ATP Molekül
Rauschanalyse ergibt die Schrittlänge
7!
Das Paradox der DNA Replikation
Drehmoment!
Mechanischer Reibungsverlust:!
Umdrehungsfrequenz: ω=600s-1 !
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M = 4π ωηR2L
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Wfric = −Mω( ) ω 2π( ) = 8π 2 ωηR2L
≈ 2 ⋅10−17Jm−1( ) ⋅ L
L=6000bp!
ATP Hydrolyse bringt 8,2 10-20J!=> L kann bis zu 2mm lang sein !!
Kann die DNA Helicase gegen die Reibung ankommen ?!
Der Reibungskoeffizient starrer Körper
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F = −γ⊥ ⋅ v
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M = −γ r ⋅ω
10!
Topoisomerasen entwirren DNA
Strick, Bensimon, Croquette et al.
Gaub/SS 2005!
BPM §5.1! 12!
Gaub/SS 2005!
BPM §5.1! 13!
Topoisomerase follows Michaelis Menton Kinetics!
Bensimon review (bilder)!
The Phage Portal Motor
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P(ds) = F0 exp −ds c( )
Stall-Kräfte von 60 pN entsprechen einem Druck von 60 bar in der Kapsel
full! empty!
T4 phage injecting DNA into liposomes
experiments!at Curie Institute!
22!
DNA/Cationic Polymers form �DNA-Polymer complexes („polyplexes“)
M. Ogris, E. Wagner, 1992!
PL-DNA toroid!
hexagonal bundels!
0.60.50.40.30.20.1q[Å-1]
Comparison of Polyplexes with various cationic polymers and DNA
b-PEI/DNA
l-PEI/DNA
PArg/DNA
PLL/DNA
linear PEI!branched PEI!
Polylysine!
Polyarginine!
locally hexagonal –!columnar structure!
Small Angle X ray Scattering �of polycation-DNA complexes
Jason Derouchy, Roland Netz, JR!
DNA / polycation!
Salt-Induced Melting Transition!
Tight bundle!
Loose bundle!
Network Phase!
J. Derouchy, R. Netz, JR !EPJE 16(1), 17-28 (2005)!
Three phases can be distinguished in �DNA / polycation mixtures
(a)! (a)! (a)!
(b)! (b)! (b)!
(c)! (b)! (b)!
„tight !bundles“!
„loose!bundles“!
„isotropic!network phase“!
Short range interactions �dominate the salt-induced melting
transition
0 400 800 1200 1600 2000
24
27
30
33
PA-DNA
NaCl Salt Concentration, I (mM)
d (A
ng)
27364554
bPEI-DNA
d (A
ng)
27303336
PL-DNA
d (A
ng)
24
32
40
48
lPEI-DNA
d (A
ng)
24
26
28
30
Sp-DNA
d (A
ng)
coexistence !regime!
critical salt concentration !c* : = onset of coexistence!
Universal scaling of polyplex structure �with reduced salt concentration c/c*
0,0 0,5 1,0 1,5 2,0 2,5 3,00
200
400
600
800
1000
ξ =
2π/Δ
qmax (A
ngst
rom
s)cs/cs* (mM NaCl)
PL-DNA PA-DNA Sp-DNA lPEI-DNA bPEI-DNA
correlation length ξ lattice constant a
Osmotic stress induced ordering transition In
tens
ity (
a.u.
)
0.40.30.20.1q (A-1)
0 % PEG
Log Π = 4.57
Log Π = 5.01
Log Π = 5.55
Log Π = 6.21
Log Π = 6.49
Log Π = 6.98
Log Π = 7.29
Log Π = 7.59
two-phase coexistence!
reversible „melting“ of hexagonal bundles with osmotic pressure!
-2,4 -2,0 -1,6 -1,2 -0,8 -0,4
0
500000
1000000
1500000
2000000
2500000
3000000
3500000
Π (
dyne
s/cm2
)
d-do (Angstroms)
compressibility of the!loose bundle regime!
Free energy of polyplexes
electrostatic attraction!
network!bundle!
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Fa = −(3 2)τ12 lB I0 Rκ[ ]K0 Dκ[ ]
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Fr = 2cr D− R( )−2 3 l−1 3
entropic repulsion!
(R. Netz)!
(Helfrich undulations of !flexible polycations)!
