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<p>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 <i>via</i> a triplet-state precursor, in contrast to RP generation <i>via</i> 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.</p><p></p>

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Direct observation of long-lived radical pair between flavin and guanine in single- and double-stranded DNA-oligomers

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年7月9日

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  • Yoshimi Oka,
  • Florian Quintes,
  • Yuri Yoshikawa,
  • Motoyasu Fujiwara,
  • Kiminori Maeda,
  • Stefan Weber,
  • Katsuya Inoue

摘要

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.