Understanding Primary Charge Separation and Revealing Fermi's Golden Rule in the Heliobacterium Modesticaldum...

Area of Science:

• Biophysics
• Quantum Chemistry

Background:

• Heliobacterium modesticaldum reaction center (HbRC) is the simplest photosystem analogue.
• Understanding charge transfer (CT) is vital for photosynthesis research.

Purpose of the Study:

• Investigate spectroscopic properties and CT processes in HbRC.
• Perform first-principles calculation of Fermi's golden rule (FGR) for HbRC.
• Analyze intrapair CT and SPP+/Acc- CT processes.

Main Methods:

• First-principles calculation of Fermi's golden rule (FGR).
• Utilized augmented models with nonsymmetrized molecular orientations.
• Employed optimally tuned screened range-separated hybrid functional (SRSH-PCM).

Main Results:

• Identified intrapair CT within the SPP molecule.
• Demonstrated symmetric hole-electron delocalization across Acc monomers.
• Calculated forward CT states are lower in energy than bright states, indicating downhill electron transfer.
• Most FGR rates are on the order of picoseconds (ps).

Conclusions:

• The study provides the first FGR calculation for HbRC.
• Findings support downhill CT pathways facilitating electron transfer.
• Electronic parameters were derived using advanced computational methods.