Study of Electron Transfer in Photosystem I Using High-Frequency EPR Spectroscopy. In Memory of Professor Klaus...

Area of Science:

• Physical Chemistry
• Biophysics
• Photosynthesis Research

Background:

• Klaus Möbius pioneered high-field/high-frequency Electron Paramagnetic Resonance (EPR) spectroscopy.
• His work focused on applying EPR to study charge transfer kinetics in photosynthetic reaction centers (RC).

Observation:

• A unique EPR setup was developed to study electron transfer kinetics in bacterial RCs and plant Photosystem I (PSI).
• Electron Spin Echo Envelope Modulation (ESEEM) measured distances between separated charges.
• Electron transfer in PSI was shown to occur primarily along the 'A' branch of redox cofactors.

Findings:

• Kinetics of forward and backward electron transfer in PSI were measured.
• The disaccharide trehalose demonstrated a bioprotective effect on electron transfer kinetics.
• Trehalose slowed electron transfer by restricting protein mobility, enabling functional activity in dried PSI.

Implications:

• Results highlight the role of hydrogen bonds and protein conformational mobility in facilitating electron transfer.
• Demonstrates trehalose's potential for preserving photosynthetic complex function under stress (anhydrobiosis).
• Advanced understanding of charge separation and transfer mechanisms in natural and artificial photosynthetic systems.