Radical cage effects in adocobinamide (axial-base-off coenzyme B12): a simple method for trapping [Ado.bul. .bul.CoII] radical pairs. A new .beta.-H elimination product from the radical pair and measurement of an unprecedentedly large cage-recombination efficiency factor, Fc .gtoreq. 0.94

1992 ◽  
Vol 114 (26) ◽  
pp. 10440-10445 ◽  
Author(s):  
Cheryl D. Garr ◽  
Richard G. Finke
Keyword(s):  
Radical Pair ◽  
Efficiency Factor ◽  
Coenzyme B12 ◽  
Large Cage ◽  
Radical Pairs ◽  
Simple Method ◽  
Recombination Efficiency ◽  
Cage Effects

scholarly journals Could radical pairs play a role in xenon-induced general anesthesia?

2020 ◽  
Author(s):  
Jordan Smith ◽  
Hadi Zadeh Haghighi ◽  
Christoph Simon
Keyword(s):  
General Anesthesia ◽  
Radical Pair ◽  
The Body ◽  
Radical Pair Mechanism ◽  
General Anesthetic ◽  
Radical Pairs ◽  
Naturally Occurring ◽  
Isotopic Dependence ◽  
Anesthetic Potency ◽  
Recombination Dynamics

ABSTRACTUnderstanding the mechanisms underlying anesthesia would be a key step towards understanding consciousness. The process of xenon-induced general anesthesia has been shown to involve electron transfer, and the potency of xenon as a general anesthetic exhibits isotopic dependence. We propose that these observations can be explained by a mechanism in which the xenon nuclear spin influences the recombination dynamics of a naturally occurring radical pair of electrons. We develop a simple model inspired by the body of work on the radical-pair mechanism in cryptochrome in the context of avian magnetoreception, and we show that our model can reproduce the observed isotopic dependence of the general anesthetic potency of xenon in mice. Our results are consistent with the idea that radical pairs of electrons with entangled spins could be important for consciousness.

scholarly journals Can disordered radical pair systems provide a basis for a magnetic compass in animals?

2009 ◽  
Vol 7 (suppl_2) ◽  
Author(s):  
Erin Hill ◽  
Thorsten Ritz
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Radical Pair ◽  
Magnetic Compass ◽  
Magnetic Field Direction ◽  
Chemical Signal ◽  
Radical Pairs ◽  
Directional Information ◽  
Minimum Number ◽  
Signal Production

A proposed mechanism for magnetic compasses in animals is that systems of radical pairs transduce magnetic field information to the nervous system. One can show that perfectly ordered arrays of radical pairs are sensitive to the direction of the external magnetic field and can thus operate, in principle, as a magnetic compass. Here, we investigate how disorder, inherent in biological cells, affects the ability of radical pair systems to provide directional information. We consider biologically inspired geometrical arrangements of ensembles of radical pairs with increasing amounts of disorder and calculate the effect of changing the direction of the external magnetic field on the rate of chemical signal production by radical pair systems. Using a previously established signal transduction model, we estimate the minimum number of receptors necessary to allow for detection of the change in chemical signal owing to changes in magnetic field direction. We quantify the required increase in the number of receptors to compensate for the signal attenuation through increased disorder. We find radical-pair-based compass systems to be relatively robust against disorder, suggesting several scenarios as to how a compass structure can be realized in a biological cell.

scholarly journals Photo-Fries rearrangements of 1-naphthyl (R)-2-phenylpropanoate in poly(vinyl acetate) and ethyl acetate: influence of medium polarity and polymer relaxation on motions of singlet radical pairs

2006 ◽  
Vol 78 (1) ◽  
pp. 31-44 ◽  
Author(s):  
Jinqi Xu ◽  
Mathew George ◽  
Richard G. Weiss
Keyword(s):  
Ethyl Acetate ◽  
Vinyl Acetate ◽  
Radical Pair ◽  
Radical Pairs ◽  
Polyethylene Films ◽  
Medium Polarity ◽  
Polymer Relaxation

Both the regio- and stereo-chemistries of the photoreactions of 1-naphthyl (R)-2-phenylpropanoate have been investigated in poly(vinyl acetate) films in their glassy (at 5ºC) and melted (at 50ºC) states and in ethyl acetate. These results are compared with those from irradiations in polyethylene films and in n-hexane. The regioselectivity of the intermediate 1-naphthoxy/(R)-2-phenylpropanoyl radical pair combinations is much higher in both the melt and glassy states of poly(vinyl acetate) films than that in the melt state of completely amorphous polyethylene films, but the stereoselectivity of intermediate prochiral 1-naphthoxy/1-phenylethyl radical pair combinations is much lower in poly(vinyl acetate). The results emphasize the need to control the ratio between the rates of radical tumbling and translation, as well as the ratio between the rates of in-cage motions and cage-escape, if high stereo- and regio-selectivities of combination products are to be achieved. A mechanistic picture of how the radicals of the intermediate pairs are affected by and interact with the various media is advanced.

Time-resolved studies of radical pairs

2009 ◽  
Vol 37 (2) ◽  
pp. 358-362 ◽  
Author(s):  
Jonathan R. Woodward ◽  
Timothy J. Foster ◽  
Alex R. Jones ◽  
Adrian T. Salaoru ◽  
Nigel S. Scrutton
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Chemical Reactions ◽  
Radical Pair ◽  
Radical Pair Mechanism ◽  
Magnetic Field Effects ◽  
Radical Pairs ◽  
Time Resolved ◽  
Field Effects ◽  
Field Sensitivity

The effect of magnetic fields on chemical reactions through the RP (radical pair) mechanism is well established, but there are few examples, in the literature, of biological reactions that proceed through RP intermediates and show magnetic field-sensitivity. The present and future relevance of magnetic field effects in biological reactions is discussed.

scholarly journals Persistent Radical Pairs Between N-Substituted Naphthalimide and Carbanion Exhibit pKa-Dependent UV-vis Absorption

2019 ◽  
Author(s):  
Xiancheng Nie ◽  
Tao Wang ◽  
Xiaoyu Chen ◽  
Wenhuan Huang ◽  
Linkun Huang ◽  
...  
Keyword(s):  
Absorption Spectrum ◽  
Radical Pair ◽  
Ambient Conditions ◽  
Radical Pairs ◽  
New Strategy ◽  
Carbon Acids ◽  
Organic Solutions

A new strategy is constructed for estimating and screening pK<sub>a</sub> values among different carbon acids under ambient conditions via the UV-vis absorption spectrum of persistent radical pair originating from an <i>N</i>-substituted naphthalimide (NNI) derivative in the presence of various carbanions in organic solutions

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 Upper bound on the biological effects of 50/60 Hz magnetic fields mediated by radical pairs

2018 ◽  
Author(s):  
P. J. Hore
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Upper Bound ◽  
Prolonged Exposure ◽  
Radical Pair ◽  
Biological Effects ◽  
Radical Pair Mechanism ◽  
Childhood Leukaemia ◽  
Radical Pairs ◽  
Increased Risk

AbstractProlonged exposure to weak (~1 μT) extremely-low-frequency (ELF, 50/60 Hz) magnetic fields has been associated with an increased risk of childhood leukaemia. One of the few biophysical mechanisms that might account for this link involves short-lived chemical reaction intermediates known as radical pairs. In this report, we use spin dynamics simulations to derive an upper bound of 10 parts per million on the effect of a 1 μT ELF magnetic field on the yield of a radical pair reaction. By comparing this figure with the corresponding effects of changes in the strength of the Earth’s magnetic field, we conclude that if exposure to such weak 50/60 Hz magnetic fields has any effect on human biology, and results from a radical pair mechanism, then the risk should be no greater than travelling a few kilometres towards or away from the geomagnetic north or south pole.

Magnetic field effects on coenzyme B12- and B6-dependent lysine 5,6-aminomutase: switching of the J-resonance through a kinetically competent radical-pair intermediate

2018 ◽  
Vol 20 (18) ◽  
pp. 13068-13074 ◽  
Author(s):  
Jun-Ru Chen ◽  
Shyue-Chu Ke
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Exchange Interaction ◽  
Radical Pair ◽  
Coenzyme B12 ◽  
Spin States ◽  
Magnetic Field Effects ◽  
Field Effects

External magnetic fields interact with lysine 5,6-aminomutase, through an immobilized radical-pair with constant and large exchange interaction, to switch on J-resonance between singlet and triplet spin states, which have different reactive fates.

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