The reaction mixture (80% DMSO, 20% buffer D) was mixed with 1 M DMPO to a final concentration of 50 mM,
transferred to a flat cell and illuminated for 5 min at 500 mol
quanta m−2 s−1 within the EPR spectrometer MiniScope MS300
(Magnettech GmbH, Berlin, Germany). The EPR conditions were
as follows; 1000 mG modulation amplitude, 13 mW microwave
power, 5 E gain. Each experiment was performed in triplicate and
involved an average of three scans.