Photosynthesis 2: Energy conversion and electron conduction in soft matter

LH-II LH-I

cytochrome c2

ATPase

cytoplasm

periplasm

ADP ATP

hbc1

H+

H+

e-

Q/QH2/Q

RC

Electron flow in photosynthesis of cyanobacteria

Electron flow in photosynthesis of purple bacteria

From Nature 411, (2001) 897, W. Kuhlbrandt.

Electron flow in photosynthesis of cyanobacteriaand Plants

backward direction: respiration = food consumption in mammals

Photosynthesis 2: Energy conversion and electron conduction in soft matter

LH-II LH-I

cytochrome c2

ATPase

cytoplasm

periplasm

ADP ATP

hbc1

H+

H+

e-

Q/QH2/Q

RC

Electron flow in photosynthesis of cyanobacteria

Electron flow in photosynthesis of purple bacteria

Role of Thermal Disorder on Electron Transfer in the Photosynthetic Reaction Center

Electron transfer is coupled to the thermal motion of thesurrounding protein.

Particle – Hole Separation in the Reaction Center and Solar Cells

proteinprotein rotated – 900 and stretched

LH-II LH-I

cytochrome c2

ATPase

cytoplasm

periplasm

ADP ATP

hbc1

H+

H+

e-

Q/QH2/Q

RC

Cytochrome c2 docking

Photosynthetic Apparatus of Purple Bacteria

Very Large Conformational Changes

Qo

2Fe2Se-

Qo

cyt c12Fe2S cyt c1

two path-ways for oxidation of Qo site

Iron Sulfur Protein head rotationcan redirect2nd electron

Sergei Izrailev

Photosynthetic Apparatus of Purple Bacteria

Very Large Conformational Changes

ATP synthaseenergy transformation(proton motive force rotation)

elastomechanical coupling

rotatory catalysis(twist conformational change ATP synthesis )

F1

F1

F0

stalk

(from Wang & Oster)

(Walker, Whilce,Fillingame)www.ks.uiuc.edu

Photosynthetic Pathway inCyanobacteria and Plants

bacterio-chlorophyll

bacterio-pheophytin

ubiquinone

Electron Carrying Molecules

chain

chain

chain

Particle – Hole Separation in the Reaction Center and Solar Cells

proteinprotein rotated – 900 and stretched

energy gap

energy gap

The energy gap is Gaussian distributed

Two State QM System Coupled to Protein Matrix

Hamiltonian

Protein matrix is a bath of oscillators linearlycoupled to the electron transfer according to

only a single oscillator considered at present!

First case: Coupling to a single oscillator

Hamiltonian

Protein matrix is a bath of oscillators linearlycoupled to the electron transfer according to

Two State QM System Coupled to Protein Matrix

Second case: Coupling to an ensemble of oscillators

Electron Transfer Process Coupled to the Protein Matrix

Rate for an ensemble of oscillators

But we don’t know all the coupling constants cj ? All we need to know is

Relaxation rate

Solution of Rate Equation

Electron Transfer Process Coupled to the Protein Matrix

Rate for an ensemble of oscillators

But we don’t know all the coupling constants cj ? All we need to know is

Relaxation rate

Electron Transfer Process Coupled to the Protein Matrix

Relaxation rate

energy gap correlation functionenergy gap

rms deviation of energy gap

1994

Temperature Dependence of Electron Transfer Rate