Does DNA sense light and magnetic fields? Hiroshima University led team proposes new biological mechanism of photomagnetic sensing

A joint research team comprising Specially Appointed Assistant Professor Yoshimi Oka and Professor Katsuya Inoue from the International Institute for Sustainability with Knotted Chiral Meta Matter (WPI-SKCM²) at Hiroshima University, along with researchers from Albert-Ludwigs-Universität Freiburg in Germany, Saitama University, and the Institute for Molecular Science, has demonstrated that the reaction occurring between DNA and flavin pigments present in living organisms when exposed to blue light is affected by weak magnetic fields that are weaker than commercial magnetic therapy devices. By elucidating the mechanism of photomagnetic sensing in DNA that could occur in vivo, which has received little attention until now, this discovery is expected to lead to an understanding of biological senses and the effects of light and magnetic fields in our living environment on health and aging. The findings were published in Communications Chemistry.

In nature, the prevailing hypothesis is that the photoreceptor protein cryptochrome functions as a biological magnetic compass in migratory birds and other organisms, sensing the direction of the geomagnetic field. The mechanism is presumed to involve flavin adenine dinucleotide (FAD), a pigment that absorbs blue light in cryptochrome, which undergoes electron transfer reactions with nearby amino acid tryptophan (Trp) when excited by light, resulting in radical pairs as reaction intermediates that can be detected as differences in reaction efficiency due to magnetic fields.

On the other hand, it has been reported that oxidative damage to DNA, which essentially should only occur through UV absorption, also occurs in the visible light region (blue light) via flavin pigments. The G radical cation of guanine (G), the most readily oxidizable base in DNA, is considered to be the putative initial intermediate based on this assumption. The effect of weak magnetic fields on reactions involving the combination of DNA G bases and flavin pigments has received little attention until now.

The mechanism by which the protein cryptochrome senses weak magnetic fields (geomagnetic field) is suggested to be mediated by spin-correlated radical pairs comprising FAD radicals and Trp radicals formed simultaneously by blue light-induced electron transfer reactions.

The research team used flavin-tethered single-stranded and double-stranded DNA oligomers and directly observed the formation of long-lived spin-correlated radical pairs comprising flavin (Fl) radicals and guanine (G) radicals through blue light-induced electron transfer reactions using time-resolved electron paramagnetic resonance (TREPR) spectroscopy. Through evaluation of reaction mechanisms using transient absorption (TA) spectroscopy and its magnetic field effects (MFE) (the ratio of product yield change in the presence of a magnetic field compared with no magnetic field), radical pair generation via a triplet state precursor was identified in flavin-tethered DNA oligomers, in contrast to the reported radical pair generation via a singlet state precursor in cryptochromes. The discovery of radical pairs in flavin-tethered DNA oligomers with microsecond lifetimes (satisfying the time requirements for magnetic sensing as intermediates) and large magnetic field effects at room temperature (65% increase in product yield under a 28 mT magnetic field compared with no magnetic field) is expected to lead to an understanding of biological magnetoreception.

These findings are expected to lead to an understanding of biological senses and the effects of light and magnetic fields in our living environment on health and aging. In particular, since the G radical cation of DNA that was the focus of this study is an initial intermediate in oxidative DNA damage and is said to have deep relevance to human health and disease, the findings may lead to applications in healthcare and aging care. Additionally, attention is also being drawn to concerted reactions with photolyase, a protein that repairs DNA damage.

Journal Information
Publication: Communications Chemistry
Title: Direct observation of long-lived radical pair between flavin and guanine in single- and double-stranded DNA-oligomers
DOI: 10.1038/s42004-025-01596-x