Cluster-Dependent Charge-Transfer Dynamics in Iron-Sulfur Proteins

Area of Science:

• Biochemistry
• Photochemistry
• Materials Science

Background:

• Iron-sulfur clusters are crucial metalloproteins involved in various biological electron transfer processes.
• Understanding their photoinduced charge-transfer dynamics is key to harnessing their potential in artificial photosynthesis and energy conversion.

Purpose of the Study:

• To investigate the photoinduced charge-transfer dynamics of five distinct iron-sulfur clusters.
• To determine how cluster size and composition influence these dynamics.
• To identify clusters suitable for long-range electron transfer and photosensitization.

Main Methods:

• Utilized laser excitation to promote iron-sulfur clusters to excited electronic states.
• Measured electronic relaxation lifetimes across different cluster types.
• Analyzed the interplay between reorganization energies and electronic state density.

Main Results:

• Electronic relaxation lifetimes varied significantly among the studied clusters.
• 1Fe-4S, 8Fe-7S, and 7Fe-9S-1Mo clusters exhibited picosecond lifetimes.
• 2Fe-2S and 4Fe-4S clusters displayed notably longer nanosecond lifetimes.
• Optimal conditions for long charge-transfer lifetimes were identified in the 2Fe-2S (Pdx) and 4Fe-4S (Fe protein) clusters.

Conclusions:

• Charge-transfer lifetimes are mediated by a balance between reorganization energies and electronic coupling.
• The 2Fe-2S and 4Fe-4S clusters are promising candidates for efficient long-range electron transfer.
• These clusters hold potential as photosensitizers for reactions like solar hydrogen production.