Work Package 3 - Biological Research

The H-cluster active center of [FeFe]-Hydrogenase can be considered a strongly correlated electronic system in which the geometrical structure, spin densities, and electronic interactions play a significant role in its molecular function. Single crystal EPR has been successfully applied to [NiFe]-Hydrogenases due to the availability of relative large crystals (0.5 x 0.5 x 1.0 mm3). However, protein crystals from [FeFe]-Hydrogenase are significantly smaller (approximately 50 times). With the development of nano-EPR we will be able to access, for the first time, protein micro-crystals of sizes used for X-ray crystallography structure determination (nanoliter to sub-nanoliter volumes). The current project will be specifically focused on the [FeFe]-Hydrogenase enzymes, with its active site shown to the right, but the methods and technology are applicable to any protein crystal.

Single crystal experiments provide:
  • Information on the eak magnetic interactions of the paramagnetic system with surrounding nuclear spins residing on ligands and protein side-chains.
  • Improvement to quantum-chemical calculations by coupling EPR data to simulation solutions.
  • Extraction of the full magnetic A- and g-tensors of the active site and the accessory [4Fe-4S] clusters. These spacial magnetic properites provide understanding of [FeFe]-Hydrogenases catalytic mechanism.

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