Transcript Electron Transfer Process Coupled to the Protein Matrix

Photosynthesis 2: Energy
conversion and electron
conduction in soft matter
Electron flow in photosynthesis of cyanobacteria
H+
ADP
Q/QH2/Q
hn
ATP cytoplasm
ATPase
bc1
RC
LH-II
LH-I
ecytochrome c2
Electron flow in photosynthesis
of purple bacteria
periplasm
H+
Electron flow in photosynthesis of cyanobacteria
and Plants
backward direction: respiration = food consumption in mammals
From Nature 411, (2001) 897, W. Kuhlbrandt.
Photosynthesis 2: Energy
conversion and electron
conduction in soft matter
Electron flow in photosynthesis of cyanobacteria
H+
ADP
Q/QH2/Q
hn
ATP cytoplasm
ATPase
bc1
RC
LH-II
LH-I
ecytochrome c2
Electron flow in photosynthesis
of purple bacteria
periplasm
H+
Role of Thermal Disorder on Electron
Transfer in the Photosynthetic Reaction Center
Electron transfer
is coupled to the
thermal motion of the
surrounding protein.
Particle – Hole Separation in the Reaction Center and Solar Cells
protein
protein rotated – 900 and stretched
Cytochrome c2 docking
+
H
ADP
Q/QH2/Q
hn
ATP cytoplasm
ATPase
bc1
RC
LH-II
LH-I
ecytochrome c2
periplasm
H+
Photosynthetic Apparatus of Purple Bacteria
Very Large Conformational Changes
two pathways for
oxidation
of Qo
esite
Qo
Iron Sulfur
Protein
head rotation
can redirect
2nd electron
Qo
2Fe2S
2Fe2S
cyt c1
cyt c1
Sergei Izrailev
Photosynthetic Apparatus of Purple Bacteria
Very Large Conformational Changes
F1
rotatory catalysis
(twist
conformational change
ATP synthesis )
(from Wang & Oster)
elastomechanical
coupling
F1
s
t
a
l
k
F0
www.ks.uiuc.edu
energy transformation ATP synthase
(Walker, Whilce,
(proton motive force
Fillingame)
rotation)
Photosynthetic Pathway in
Cyanobacteria and Plants
Electron Carrying Molecules
bacteriochlorophyll
chain
bacteriopheophytin
chain
ubiquinone
chain
Particle – Hole Separation in the Reaction Center and Solar Cells
protein
protein rotated – 900 and stretched
The energy gap is
Gaussian distributed
energy gap
energy gap
Two State QM System Coupled to Protein Matrix
First case: Coupling to a single oscillator
Hamiltonian
Protein matrix is a bath of oscillators linearly
coupled to the electron transfer according to
only a single oscillator considered at present!
Two State QM System Coupled to Protein Matrix
Second case: Coupling to an ensemble of oscillators
Hamiltonian
Protein matrix is a bath of oscillators linearly
coupled to the electron transfer according to
Electron Transfer Process Coupled to the Protein Matrix
Rate for an ensemble of oscillators
Relaxation rate
But we don’t know all the coupling constants cj ? All
we need to know is
Solution of Rate Equation
Electron Transfer Process Coupled to the Protein Matrix
Rate for an ensemble of oscillators
Relaxation rate
But we don’t know all the coupling constants cj ? All
we need to know is
Electron Transfer Process Coupled to the Protein Matrix
Relaxation rate
1994
energy gap
energy gap correlation function
rms deviation of energy gap
Temperature Dependence of Electron Transfer Rate