Kobe University Links Chirality-Induced Spin Selectivity in Frog Cryptochrome to a Stronger Calculated Magnetic Compass Signal, J. Phys. Chem. Lett., 30 October 2026
What Kobe University measured, inferred and calculated in frog cryptochrome
Quentir Medicine Monitor
Evidence-based insights for quantum medicine.
Migrating birds appear to read the direction of Earth's magnetic field with their eyes, and the leading explanation places the sensor in a blue-light protein called cryptochrome. A team led by Professor Yasuhiro Kobori at Kobe University has recorded electron-spin spectra from a frog cryptochrome, interpreted them as the handed twisting of a single amino acid, and calculated that this effect would strengthen the directional signal a magnetic compass of this kind depends on.
The work appeared in The Journal of Physical Chemistry Letters on 30 October 2026, under an open CC BY license. Kobe University, Toho University, Saitama University and the Nagoya Institute of Technology announced it on 27 October, and Japan's National Institutes for Quantum Science and Technology (QST) carried the joint press release on its Q-LEAP program pages. The co-authors include Masaaki Fuki and Misato Hamada at Kobe, Tatsuya Iwata at Toho University's Faculty of Pharmaceutical Sciences, Hiroki Nagashima at Saitama University, Hideki Kandori at the Nagoya Institute of Technology and Stefan Weber at the University of Freiburg.
The central finding concerns chirality-induced spin selectivity, often shortened to CISS: a right- or left-handed molecular structure can favor electrons of one spin orientation as charge moves through it. The team used time-resolved electron spin resonance, a method that reads unpaired electron spins through microwave absorption and emission, to record spin spectra during the light reaction. The authors interpret those spectra as a handed rotation of a tryptophan residue that leaves a CISS signature of a few percent in the spin state of the protein. The compass effect itself is a calculation built on that interpretation.
For a clinical reader, the result belongs to basic quantum biology. It concerns a frog protein made in bacteria, measured frozen, and a calculated compass effect. The authors mention weak magnetic sensors built from biomolecules as a possible later application, and nothing in the paper tests one.
The protein was cryptochrome-DASH from the African clawed frog, Xenopus laevis, expressed in and purified from E. coli. It serves here as a model system: the paper states that this frog protein is not itself a candidate magnetoreceptor, which is why the compass calculation later borrows the structure of a bird cryptochrome. Cryptochromes carry a pigment, flavin adenine dinucleotide (FAD), that absorbs blue light. Once excited, the FAD pulls an electron step by step along a chain of three tryptophan residues, and each step leaves a pair of separated charges, each with an unpaired electron. Such a radical pair is magnetic, and its two spins can sit in a singlet or a triplet state, which react differently.