Following radical pair reactions in solution: a step change in sensitivity using cavity ring-down detection.

Area of Science:

• Chemical Physics
• Biophysics
• Spectroscopy

Background:

• Investigating radical pair intermediates in biological systems is challenging due to low sensitivity of optical techniques.
• Understanding spin-selective and magneto-sensitive reaction yields is key for bird migration mechanisms and electromagnetic radiation health effects.

Purpose of the Study:

• Demonstrate the capabilities of cavity-enhanced techniques, specifically cavity ring-down spectroscopy (CRDS), for monitoring radical reactions and magnetic field effects (MFEs).
• Highlight the advantages of CRDS over conventional flash-photolysis techniques, including submicrosecond time-resolution, high sensitivity, and small sample volumes.

Main Methods:

• Utilized cavity ring-down spectroscopy (CRDS) for monitoring radical recombination reactions and associated magnetic field effects (MFEs).
• Employed pump-probe experiments to measure MFEs in photoinduced radical pair reactions involving lysozyme and photosensitizers.
• Applied CRDS to an in vitro study of intramolecular electron transfer in Escherichia coli photolyase.

Main Results:

• CRDS demonstrated submicrosecond time-resolution and high sensitivity (10^-6 absorbance units) for monitoring radical reactions.
• Observed CRDS-measured MFEs in pump-probe experiments, showcasing sensitivity gains and sample-volume minimization compared to flash photolysis.
• Successfully applied CRDS to study intramolecular electron transfer in E. coli photolyase.

Conclusions:

• CRDS is a powerful technique for studying radical pair intermediates and their magnetic field effects in biological systems.
• The high sensitivity and time-resolution of CRDS offer significant advantages over conventional methods.
• This technique has implications for understanding biological magnetoreception and potential health effects of electromagnetic radiation.