1. Cluster-Dependent Charge-Transfer Dynamics in Iron-Sulfur Proteins.
- Author
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Mao Z, Liou SH, Khadka N, Jenney FE Jr, Goodin DB, Seefeldt LC, Adams MWW, Cramer SP, and Larsen DS
- Subjects
- Azotobacter vinelandii chemistry, Catalytic Domain, Electron Transport, Ferredoxins chemistry, Models, Molecular, Oxidation-Reduction, Oxidoreductases chemistry, Protein Conformation, Pseudomonas putida chemistry, Pyrococcus furiosus chemistry, Rubredoxins chemistry, Bacteria chemistry, Bacterial Proteins chemistry, Iron-Sulfur Proteins chemistry
- Abstract
Photoinduced charge-transfer dynamics and the influence of cluster size on the dynamics were investigated using five iron-sulfur clusters: the 1Fe-4S cluster in Pyrococcus furiosus rubredoxin, the 2Fe-2S cluster in Pseudomonas putida putidaredoxin, the 4Fe-4S cluster in nitrogenase iron protein, and the 8Fe-7S P-cluster and the 7Fe-9S-1Mo FeMo cofactor in nitrogenase MoFe protein. Laser excitation promotes the iron-sulfur clusters to excited electronic states that relax to lower states. The electronic relaxation lifetimes of the 1Fe-4S, 8Fe-7S, and 7Fe-9S-1Mo clusters are on the picosecond time scale, although the dynamics of the MoFe protein is a mixture of the dynamics of the latter two clusters. The lifetimes of the 2Fe-2S and 4Fe-4S clusters, however, extend to several nanoseconds. A competition between reorganization energies and the density of electronic states (thus electronic coupling between states) mediates the charge-transfer lifetimes, with the 2Fe-2S cluster of Pdx and the 4Fe-4S cluster of Fe protein lying at the optimum leading to them having significantly longer lifetimes. Their long lifetimes make them the optimal candidates for long-range electron transfer and as external photosensitizers for other photoactivated chemical reactions like solar hydrogen production. Potential electron-transfer and hole-transfer pathways that possibly facilitate these charge transfers are proposed.
- Published
- 2018
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