Cluster-Dependent Charge-Transfer Dynamics in Iron-Sulfur Proteins
Document Type
Article
Journal/Book Title
Biochemistry
Publication Date
1-5-2018
Publisher
American Chemical Society
Volume
57
Issue
6
First Page
978
Last Page
990
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.
Recommended Citation
Mao, Z., Liou, S.-H., Khadka, N., Jenney, F. E., Goodin, D. B., Seefeldt, L. C., Adams, M. W. W., Cramer, S., and Larsen, D. S. (2018) Cluster Dependent Charge-Transfer Dynamics in Iron-Sulfur Proteins. Biochemistry 57, 978–990.
