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Updated: Sep 16, 2025

Real-time Observation of the DNA Strand Exchange Reaction Mediated by Rad51
Published on: February 13, 2019
Direct observation of long-lived radical pair between flavin and guanine in single- and double-stranded DNA-oligomers
Yoshimi Oka1,2, Florian Quintes3, Yuri Yoshikawa4
1Research Promotion Institute, Oita University, Oita-shi, Oita, Japan. yoshimo@hiroshima-u.ac.jp.
Abstract:
The mechanism by which cryptochrome (CRY) proteins are capable of sensing weak magnetic fields (e.g., the geomagnetic field: ~50 μT) was suggested to be mediated by spin-correlated radical pairs (SCRPs) comprising a flavin adenine dinucleotide (FAD) radical and a tryptophan (Trp) radical which are formed simultaneously by light-induced electron transfer (ET). Here, we provide evidence for direct photoinduced ET that leads to long-lived SCRPs comprising a flavin (Fl) radical and a guanine (G) radical in flavin-tethered single- and double-stranded DNA oligomers by using time-resolved electron paramagnetic resonance (TREPR) spectroscopy. Transient absorption (TA) spectroscopy and its magnetic field effect (MFE) identified RP generation via a triplet-state precursor, in contrast to RP generation via a singlet-state precursor in CRY. Our findings of RPs in Fl-DNA oligomers having microsecond-long lifetimes and capable of exerting a large MFE at room temperature may significantly impact on our understanding of biological magnetoreception.
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