Radical-pair mechanism: Difference between revisions
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In [[quantum biology]], the '''[[Radical (chemistry)|radical]]-pair mechanism''' is a proposed [[Spin chemistry|spin-chemistry]] explanation for [[magnetoreception]], the ability for an organism to sense weak magnetic fields. It has been significantly studied in the context of [[bird migration]]. | In [[quantum biology]], the '''[[Radical (chemistry)|radical]]-pair mechanism''' is a proposed [[Spin chemistry|spin-chemistry]] explanation for [[magnetoreception]], the ability for an organism to sense weak magnetic fields. It has been significantly studied in the context of [[bird migration]]. | ||
== Mechanism == | == Mechanism == | ||
A [[Radical (chemistry)|radical]] is a molecule with an unpaired [[valence electron]]; thus, a pair of radicals is a radical pair. In the radical-pair mechanism, the unpaired electrons of the radical pair are [[Spin (physics)|spin]]-correlated, oscillating between a [[singlet state]] and a [[triplet state]]. Importantly, the radical pair spin state can interact with its environment, particularly with external magnetic fields, which influences which state it will be in.<ref name=":1" /> These state changes caused by external magnetic fields affect the dynamics of subsequent chemical reactions involving the radical pairs, which can result in different biological effects.<ref name=":3">{{Cite web |title=The radical-pair mechanism as a paradigm for the emerging science of quantum biology |url=https://arxiv.org/html/1512.00450v2 |access-date=2026-09-23 |website=arxiv.org|date=2016|last=Kominis|first=Iannis K.}}</ref> | A [[Radical (chemistry)|radical]] is a molecule with an unpaired [[valence electron]]; thus, a pair of radicals is a radical pair. In the radical-pair mechanism, the unpaired electrons of the radical pair are [[Spin (physics)|spin]]-correlated, oscillating between a [[singlet state]] and a [[triplet state]]. Importantly, the radical pair spin state can interact with its environment, particularly with external magnetic fields, which influences which state it will be in.<ref name=":1">{{Cite journal |last=Zadeh-Haghighi |first=Hadi |last2=Simon |first2=Christoph |date=2022-08-01 |title=Magnetic field effects in biology from the perspective of the radical pair mechanism |url=https://doi.org/10.1098/rsif.2022.0325 |journal=Journal of The Royal Society Interface |volume=19 |issue=193 |pages= |doi=10.1098/rsif.2022.0325 |issn=1742-5689}}</ref> These state changes caused by external magnetic fields affect the dynamics of subsequent chemical reactions involving the radical pairs, which can result in different biological effects.<ref name=":3">{{Cite web |title=The radical-pair mechanism as a paradigm for the emerging science of quantum biology |url=https://arxiv.org/html/1512.00450v2 |access-date=2026-09-23 |website=arxiv.org|date=2016|last=Kominis|first=Iannis K.}}</ref> | ||
== Biological impacts == | == Biological impacts == | ||
=== Avian magnetoreception === | === Avian magnetoreception === | ||
[[Flavin group|Flavin]]-[[tryptophan]] radical pairs created by [[Photochemistry|photochemical]] processes in [[Cryptochrome|cryptochromes]] have been shown to exhibit sensitivity to [[Static magnetic field|static magnetic fields]] due to the radical-pair mechanism | [[Flavin group|Flavin]]-[[tryptophan]] radical pairs with millisecond lifetimes created by [[Photochemistry|photochemical]] processes in [[Cryptochrome|cryptochromes]] have been shown to exhibit sensitivity to [[Static magnetic field|static magnetic fields]] due to the radical-pair mechanism. These cryptochromes are the primary proteins involved in [[avian magnetoreception]].<ref name=":1" /><ref name=":2" /> | ||
=== Human brain interactions === | === Human brain interactions === | ||
Revision as of 20:50, 23 September 2026
In quantum biology, the radical-pair mechanism is a proposed spin-chemistry explanation for magnetoreception, the ability for an organism to sense weak magnetic fields. It has been significantly studied in the context of bird migration.
Mechanism
A radical is a molecule with an unpaired valence electron; thus, a pair of radicals is a radical pair. In the radical-pair mechanism, the unpaired electrons of the radical pair are spin-correlated, oscillating between a singlet state and a triplet state. Importantly, the radical pair spin state can interact with its environment, particularly with external magnetic fields, which influences which state it will be in.[1] These state changes caused by external magnetic fields affect the dynamics of subsequent chemical reactions involving the radical pairs, which can result in different biological effects.[2]
Biological impacts
Avian magnetoreception
Flavin-tryptophan radical pairs with millisecond lifetimes created by photochemical processes in cryptochromes have been shown to exhibit sensitivity to static magnetic fields due to the radical-pair mechanism. These cryptochromes are the primary proteins involved in avian magnetoreception.[1][3]
Human brain interactions
The radical-pair effect is thought to play a role in the use of xenon as an anaesthetic due to observed electron-spin resonance signals. Xenon interacts with tryptophan, which forms a radical pair and can subsequently interact with NMDA receptors. Radical-pair models have similarly been applied to the use of lithium salts as mood stabilizers or impactors of the circadian clock, as well as to the effects of hypomagnetic fields (i.e. magnetic fields with less intensity than the Earth's magnetic field) on the attenuation of neurogenesis in adults; all of these models have been proposed to involve radical pairs of FADH and oxygen).[1]
Discovery
The radical-pair mechanism was first described in the late 1960s to explain the phenomena of chemically-induced dynamic electron polarization (CIDEP) and chemically-induced dynamic nuclear polarization (CIDNP): that is, anomalously large electron spin resonance and nuclear magnetic resonance signal values in organic-molecule chemical reactions, respectively.[2] It was first applied to a theory of avian magnetoreception in the 1970s by Schulten et al.[3]
See also
References
- ↑ 1.0 1.1 1.2 Zadeh-Haghighi, Hadi; Simon, Christoph (2022-08-01). "Magnetic field effects in biology from the perspective of the radical pair mechanism". Journal of The Royal Society Interface 19 (193). doi:. ISSN 1742-5689. https://doi.org/10.1098/rsif.2022.0325.
- ↑ 2.0 2.1 Kominis, Iannis K. (2016). "The radical-pair mechanism as a paradigm for the emerging science of quantum biology". https://arxiv.org/html/1512.00450v2.
- ↑ 3.0 3.1 Adams, Betony; Sinayskiy, Ilya; Petruccione, Francesco (2018-10-24). "An open quantum system approach to the radical pair mechanism" (in en). Scientific Reports (Nature Publishing Group) 8 (1): 15719. doi:. ISSN 2045-2322. https://www.nature.com/articles/s41598-018-34007-4.