Quantum interferences and electron transfer in photosystem I.
Nicolas Renaud1, Daniel Powell, Mahdi Zarea
1Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, USA. n-renaud@northwestern.edu
The Journal of Physical Chemistry. A
|November 9, 2012
Summary
Electron transfer in photosystem I (PSI) was simulated using DFT calculations. Quantum effects like coherence and interference significantly influence electron transfer efficiency, especially with specific energy differences.
Area of Science:
- Biophysics
- Quantum Chemistry
Background:
- Photosystem I (PSI) is crucial for photosynthesis, facilitating electron transfer from the special pair to iron-sulfur clusters.
- Understanding electron transfer dynamics in PSI is key to comprehending energy conversion in biological systems.
Purpose of the Study:
- To investigate the electron transfer process within the PSI reaction center.
- To elucidate the role of quantum phenomena, such as coherence and interference, in electron transfer dynamics.
- To determine the impact of energetic fluctuations and asymmetries on transfer efficiency.
Main Methods:
- Density Functional Theory (DFT) calculations for electronic structure.
- Stochastic surrogate Hamiltonian approach for charge transfer dynamics simulation.
- Analysis of coherent propagation, energy relaxation, and decoherence.
Main Results:
- Simulated electron transfer times range from subpicoseconds to nanoseconds.
- Predicted coherent oscillations lasting for several picoseconds.
- Demonstrated that quantum interferences can enhance or inhibit electronic density propagation.
- Showed that random fluctuations suppress quantum interferences, leading to classical transport.
Conclusions:
- Long-lasting coherences in PSI play a significant role in electron transfer efficiency.
- A specific energy difference (0.15 eV) between phylloquinone sites enhances electron transfer, even with strong fluctuations.
- Quantum mechanical effects are vital for efficient electron transport in biological systems.
Related Concept Videos
01:27Photosystem I
Although structurally similar to photosystem II (PSII), photosystem I (PSI) is has a different electron supplier and electron acceptor.
Both these photosystems work in concert. An excited electron from PSII is relayed to PSI via an electron transport chain in the thylakoid membrane of the chloroplast, which is comprised of the carrier molecule plastoquinone, the dual-protein cytochrome complex, and plastocyanin. As electrons move between PSII and PSI, they lose energy and must be re-energized...
Both these photosystems work in concert. An excited electron from PSII is relayed to PSI via an electron transport chain in the thylakoid membrane of the chloroplast, which is comprised of the carrier molecule plastoquinone, the dual-protein cytochrome complex, and plastocyanin. As electrons move between PSII and PSI, they lose energy and must be re-energized...
01:22Photosystem II
The multi-protein complex photosystem II (PS II) harvests photons and transfers their energy through its bound pigments to its reaction center, and ultimately to photosystem I (PSI) through the electron transport chain. The pigments responsible for caputirng the light energy in photosystems include chlorophyll a, chlorophyll b, and carotenoids.
The pigment molecules are arranged across two photosystem domains — the antenna complex and the reaction center. The main aim of the pigment molecules...
The pigment molecules are arranged across two photosystem domains — the antenna complex and the reaction center. The main aim of the pigment molecules...
01:34The Z-Scheme of Electron Transport in Photosynthesis
The light reactions of photosynthesis assume a linear flow of electrons from water to NADP+. During this process, light energy drives the splitting of water molecules to produce oxygen. However, oxidation of water molecules is a thermodynamically unfavorable reaction and requires a strong oxidizing agent. This is accomplished by the first product of light reactions: oxidized P680 (or P680+), the most powerful oxidizing agent known in biology. The oxidized P680 that acquires an electron from the...
01:29The Photochemical Reaction Center
Reaction centers are pigment-protein complexes that initiate energy conversion from photons to chemical entities. Therefore, photochemical reaction center is a more appropriate term that describes these complexes. The Nobel laureates Robert Emerson and William Arnold provided the first experimental evidence of photochemical reaction centers by demonstrating the participation of nearly 2,500 chlorophyll molecules for the release of just one molecule of oxygen. Despite thousands of photosynthetic...
01:32Photosystems
Photosystems are multiprotein complexes that form the functional units of photosynthesis in plants, algae, and cyanobacteria. They are found embedded in the membrane of tiny sac-like structures called thylakoids placed inside the chloroplast.
Functioning of Photosystems
Photosystems contain many pigment molecules, such as chlorophylls and carotenoids, arranged in a particular organization across two domains — the antenna complex and the reaction center. The main aim of the pigment molecules...
Functioning of Photosystems
Photosystems contain many pigment molecules, such as chlorophylls and carotenoids, arranged in a particular organization across two domains — the antenna complex and the reaction center. The main aim of the pigment molecules...
01:43Electron Transport Chain: Complex III and IV
During the electron transport chain, electrons from NADH and FADH2 are first transferred to complexes I and II, respectively. These two complexes then transfer the electrons to ubiquinol, which carries them further to complex III. Complex III passes the electrons across the intermembrane space to Cyt c, which carries them further to complex IV. Complex IV donates electrons to oxygen and reduces it to water. As electrons pass through complexes I, III, and IV, the energy released aids the pumping...