scholarly journals Alternative radical pairs for cryptochrome-based magnetoreception

2014 ◽  
Vol 11 (95) ◽  
pp. 20131063 ◽  
Author(s):  
Alpha A. Lee ◽  
Jason C. S. Lau ◽  
Hannah J. Hogben ◽  
Till Biskup ◽  
Daniel R. Kattnig ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Properties ◽  
Radical Pair ◽  
Spin Dynamics ◽  
Hyperfine Interactions ◽  
Quantum Spin ◽  
Photochemical Reactions ◽  
Asymmetric Distribution ◽  
Tryptophan Residues ◽  
Dynamics Simulations

There is growing evidence that the remarkable ability of animals, in particular birds, to sense the direction of the Earth's magnetic field relies on magnetically sensitive photochemical reactions of the protein cryptochrome. It is generally assumed that the magnetic field acts on the radical pair [FAD •− TrpH • + ] formed by the transfer of an electron from a group of three tryptophan residues to the photo-excited flavin adenine dinucleotide cofactor within the protein. Here, we examine the suitability of an [FAD •− Z • ] radical pair as a compass magnetoreceptor, where Z • is a radical in which the electron spin has no hyperfine interactions with magnetic nuclei, such as hydrogen and nitrogen. Quantum spin dynamics simulations of the reactivity of [FAD •− Z • ] show that it is two orders of magnitude more sensitive to the direction of the geomagnetic field than is [FAD •− TrpH • + ] under the same conditions (50 µT magnetic field, 1 µs radical lifetime). The favourable magnetic properties of [FAD •− Z • ] arise from the asymmetric distribution of hyperfine interactions among the two radicals and the near-optimal magnetic properties of the flavin radical. We close by discussing the identity of Z • and possible routes for its formation as part of a spin-correlated radical pair with an FAD radical in cryptochrome.

scholarly journals Exploration of the close chemical space of tryptophan and tyrosine reveals importance of hydrophobicity in CW-photo-CIDNP performances

2021 ◽  
Vol 2 (1) ◽  
pp. 321-329
Author(s):  
Felix Torres ◽  
Alois Renn ◽  
Roland Riek
Keyword(s):  
Magnetic Field ◽  
Nuclear Polarization ◽  
Continuous Wave ◽  
Radical Pair ◽  
Chemical Space ◽  
Spin Dynamics ◽  
Basic Mechanism ◽  
Chemical Library ◽  
Chemically Induced ◽  
Small Chemical

Abstract. Sensitivity being one of the main hurdles of nuclear magnetic resonance (NMR) can be gained by polarization techniques including chemically induced dynamic nuclear polarization (CIDNP). Kaptein demonstrated that the basic mechanism of the CIDNP arises from spin sorting based on coherent electron–electron nuclear spin dynamics during the formation and the recombination of a radical pair in a magnetic field. In photo-CIDNP of interest here the radical pair is between a dye and the molecule to be polarized. Here, we explore continuous-wave (CW) photo-CIDNP (denoted CW-photo-CIDNP) with a set of 10 tryptophan and tyrosine analogues, many of them newly identified to be photo-CIDNP active, and we observe not only signal enhancement of 2 orders of magnitude for 1H at 600 MHz (corresponding to 10 000 times in measurement time) but also reveal that polarization enhancement correlates with the hydrophobicity of the molecules. Furthermore, the small chemical library established indicates the existence of many photo-CIDNP-active molecules.

scholarly journals Radical pairs may play a role in microtubule reorganization

2021 ◽  
Author(s):  
Hadi ZADEH-HAGHIGHI ◽  
Christoph Simon
Keyword(s):  
Magnetic Field ◽  
Radical Pair ◽  
Spin Dynamics ◽  
Radical Pair Mechanism ◽  
Magnetic Field Effects ◽  
Radical Pairs ◽  
Quantum Theories ◽  
Mechanism Model ◽  
Field Effects ◽  
Isotopic Dependence

The exact mechanism behind general anesthesia remains an open question in neuroscience. It has been proposed that anesthetics selectively prevent consciousness and memory via acting on microtubules (MTs). It is known that the magnetic field modulates MT organization. A recent study shows that a radical pair model can explain the isotope effect in xenon-induced anesthesia and predicts magnetic field effects on anesthetic potency. Further, reactive oxygen species are also implicated in MT stability and anesthesia. Based on a simple radical pair mechanism model and a simple mathematical model of MT organization, we show that magnetic fields can modulate spin dynamics of naturally occurring radical pairs in MT. We show that the spin dynamics influence a rate in the reaction cycle, which translates into a change in the MT density. We can reproduce magnetic field effects on the MT concentration that have been observed. Our model also predicts additional effects at slightly higher fields. Our model further predicts that the effect of zinc on the MT density exhibits isotopic dependence. The findings of this work make a connection between microtubule-based and radical pair-based quantum theories of consciousness.

scholarly journals Radical pairs can explain magnetic field and lithium effects on the circadian clock

2022 ◽  
Vol 12 (1) ◽  
Author(s):  
Hadi Zadeh-Haghighi ◽  
Christoph Simon
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Circadian Clock ◽  
Spin Dynamics ◽  
Hyperfine Interactions ◽  
Oscillator Model ◽  
Radical Pair Mechanism ◽  
Dependent Manner ◽  
Radical Pairs ◽  
Chemical Oscillator

AbstractDrosophila’s circadian clock can be perturbed by magnetic fields, as well as by lithium administration. Cryptochromes are critical for the circadian clock. Further, the radical pairs in cryptochrome also can explain magnetoreception in animals. Based on a simple radical pair mechanism model of the animal magnetic compass, we show that both magnetic fields and lithium can influence the spin dynamics of the naturally occurring radical pairs and hence modulate the circadian clock’s rhythms. Using a simple chemical oscillator model for the circadian clock, we show that the spin dynamics influence a rate in the chemical oscillator model, which translates into a change in the circadian period. Our model can reproduce the results of two independent experiments, magnetic field and lithium effects on the circadian clock. Our model predicts that stronger magnetic fields would shorten the clock’s period. We also predict that lithium influences the clock in an isotope-dependent manner. Furthermore, our model also predicts that magnetic fields and hyperfine interactions modulate oxidative stress. The findings of this work suggest that the quantum nature of radical pairs might play roles in the brain, as another piece of evidence in addition to recent results on xenon anesthesia and lithium effects on hyperactivity.

scholarly journals Quantum spin dynamics of the antiferromagnetic linear chain in zero and nonzero magnetic field

1981 ◽  
Vol 24 (3) ◽  
pp. 1429-1467 ◽  
Author(s):  
Gerhard Müller ◽  
Harry Thomas ◽  
Hans Beck ◽  
Jill C. Bonner
Keyword(s):  
Magnetic Field ◽  
Spin Dynamics ◽  
Linear Chain ◽  
Quantum Spin

scholarly journals Cryptochrome magnetoreception: four tryptophans could be better than three

2021 ◽  
Vol 18 (184) ◽  
Author(s):  
Siu Ying Wong ◽  
Yujing Wei ◽  
Henrik Mouritsen ◽  
Ilia A. Solov'yov ◽  
P. J. Hore
Keyword(s):  
Dynamic Equilibrium ◽  
Radical Pair ◽  
Spin Dynamics ◽  
Photoreceptor Cells ◽  
Kinetic Properties ◽  
Radical Pairs ◽  
Magnetic Sensing ◽  
The Third ◽  
A Chain ◽  
Dynamics Simulations

The biophysical mechanism of the magnetic compass sensor in migratory songbirds is thought to involve photo-induced radical pairs formed in cryptochrome (Cry) flavoproteins located in photoreceptor cells in the eyes. In Cry4a—the most likely of the six known avian Crys to have a magnetic sensing function—four radical pair states are formed sequentially by the stepwise transfer of an electron along a chain of four tryptophan residues to the photo-excited flavin. In purified Cry4a from the migratory European robin, the third of these flavin–tryptophan radical pairs is more magnetically sensitive than the fourth, consistent with the smaller separation of the radicals in the former. Here, we explore the idea that these two radical pair states of Cry4a could exist in rapid dynamic equilibrium such that the key magnetic and kinetic properties are weighted averages. Spin dynamics simulations suggest that the third radical pair is largely responsible for magnetic sensing while the fourth may be better placed to initiate magnetic signalling particularly if the terminal tryptophan radical can be reduced by a nearby tyrosine. Such an arrangement could have allowed independent optimization of the essential sensing and signalling functions of the protein. It might also rationalize why avian Cry4a has four tryptophans while Crys from plants have only three.

scholarly journals The quantum needle of the avian magnetic compass

2016 ◽  
Vol 113 (17) ◽  
pp. 4634-4639 ◽  
Author(s):  
Hamish G. Hiscock ◽  
Susannah Worster ◽  
Daniel R. Kattnig ◽  
Charlotte Steers ◽  
Ye Jin ◽  
...  
Keyword(s):  
Migratory Birds ◽  
Radical Pair ◽  
Spin Dynamics ◽  
Energy Levels ◽  
Magnetic Compass ◽  
Spin Coherence ◽  
Radical Pairs ◽  
Sharp Feature ◽  
In The Wild ◽  
Dynamics Simulations

Migratory birds have a light-dependent magnetic compass, the mechanism of which is thought to involve radical pairs formed photochemically in cryptochrome proteins in the retina. Theoretical descriptions of this compass have thus far been unable to account for the high precision with which birds are able to detect the direction of the Earth's magnetic field. Here we use coherent spin dynamics simulations to explore the behavior of realistic models of cryptochrome-based radical pairs. We show that when the spin coherence persists for longer than a few microseconds, the output of the sensor contains a sharp feature, referred to as a spike. The spike arises from avoided crossings of the quantum mechanical spin energy-levels of radicals formed in cryptochromes. Such a feature could deliver a heading precision sufficient to explain the navigational behavior of migratory birds in the wild. Our results (i) afford new insights into radical pair magnetoreception, (ii) suggest ways in which the performance of the compass could have been optimized by evolution, (iii) may provide the beginnings of an explanation for the magnetic disorientation of migratory birds exposed to anthropogenic electromagnetic noise, and (iv) suggest that radical pair magnetoreception may be more of a quantum biology phenomenon than previously realized.

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