Electron spin exchange relaxation of radicals in low magnetic field

Shakirov, S. R.; Purtov, P. A.; Grishin, Yu. A.; Bagryanskaya, Elena G.

doi:10.1080/00268970600564976

Cited by 3 publications

(3 citation statements)

References 21 publications

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“…In the decade following, a significant body of work, both experimental and theoretical (Stass et al 2000;Weaver et al 2000;Timmel et al 2001;Woodward et al 2001;Weaver 2002;Cintolesi et al 2003;Henbest et al 2004;Ritz et al 2004Ritz et al , 2009Vink & Woodward 2004;O'Dea et al 2005;Rodgers et al 2005Rodgers et al , 2007Thalau et al 2005;Vaughan & Weaver 2005;Shakirov et al 2006;Solov'yov et al 2007;Woodward & Vink 2007;Efimova & Hore 2008;Maeda et al 2008;Miura & Murai 2008;Solov'yov & Schulten 2009;Hill & Ritz 2010;Lau et al 2010), has advanced our information and understanding of how a putative radical-pair magnetoreceptor should be designed so as to be well suited to detect the geomagnetic field. Behavioural studies have provided more information about the functional properties of magnetic compasses in a variety of animals (Rappl et al 2000;Wiltschko et al 2000aWiltschko et al ,b, 2001Wiltschko et al , 2002bWiltschko et al , 2003aWiltschko et al , 2004aWiltschko et al ,b, 2005Wiltschko et al , 2006Wiltschko et al , 2007aÅ kesson et al 2001;Phillips et al 2001Phillips et al , 2002Muheim et al 2002Muheim et al , 2006Irwin & Loh...…”

Section: Introductionmentioning

confidence: 99%

Photoreceptor-based magnetoreception: optimal design of receptor molecules, cells, and neuronal processing

Ritz

Ahmad

Mouritsen

et al. 2010

J. R. Soc. Interface.

124

113

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The sensory basis of magnetoreception in animals still remains a mystery. One hypothesis of magnetoreception is that photochemical radical pair reactions can transduce magnetic information in specialized photoreceptor cells, possibly involving the photoreceptor molecule cryptochrome. This hypothesis triggered a considerable amount of research in the past decade. Here, we present an updated picture of the radical-pair photoreceptor hypothesis. In our review, we will focus on insights that can assist biologists in their search for the elusive magnetoreceptors.

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Section: Introductionmentioning

confidence: 99%

Photoreceptor-based magnetoreception: optimal design of receptor molecules, cells, and neuronal processing

Ritz

Ahmad

Mouritsen

et al. 2010

J. R. Soc. Interface.

124

113

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“…Its rate is given by . (22) At ω e >> a, expression (22) is exactly the same as relationship (20), but in a weak magnetic field (ω e << a) the relaxation rate 1/T cr → 0 because C 1 ≈ C 2 .…”

Section: Spin Relaxation Due To Modulation Of Isotropic Hyperfine Intmentioning

confidence: 82%

“…Accord ing to calculations, the slopes of the concentration de pendences in strong and weak (at a resonance frequency of 94 MHz) magnetic fields should differ by a factor of 1.34, which is in reasonable agreement with the experi mental data. 20 Note that as in the case of spin rotational relaxation (see above) ESE in strong magnetic fields induces only the electron spin flip transitions, but in weak magnetic fields relaxation becomes electron nuclear in character. This salient feature of ESE induced relaxation should be taken into account when analyzing the magnetic field dependences of the CIDNP in the reactions involving radical ions and stable nitroxyl radicals in weak mag netic fields, 44 because the effect of this feature on the kinetics of spin polarization and on the EPR spectra is mainly determined by the initial spin level populations in radicals.…”

Section: Spin Relaxation Induced By Electron Spin Exchangementioning

confidence: 96%

Electron spin relaxation of radicals in weak magnetic fields

et al. 2006

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The review summarizes the results of studies on specific features of spin relaxation of radicals in liquids in weak magnetic fields.Key words: electron spin relaxation, weak magnetic field, free radicals, electron paramag netic resonance, spin polarization, chemically induced dynamic electron polarization.Many photochemical reactions involve radical stages. The interaction of external constant and alternating mag netic fields with electron and nuclear spins of intermedi ate radicals is the reason for the magnetic field and spin effects in radical chemical reactions. One of the key pa rameters determining the magnitude of the magnetic field effects is the spin relaxation rate of the intermediate radi cals. 1,2 In the case of long lived radical pairs (RPs), e.g., RPs in micellar solutions, 2 radical ion pairs, 3 biradicals, 4 etc., the spin relaxation is one of the main processes de termining the probability of RP recombination. The spin relaxation rate is an important parameter used in calcula tions of the magnetic field effect, 2 EPR spectra, 5 kinetics of chemically induced dynamic electron polarization (CIDEP), 1,6 optically detected EPR spectra, 3 stimulated nuclear polarization (SNP) spectra and kinetics, 7 etc. Usu ally, the magnetic field effects and the CIDEP, SNP, and optically detected EPR spectra are calculated assuming additive contributions of (i) electron relaxation in indi vidual radicals due to the interaction between an electron in a given radical and surrounding nuclei (modulation of anisotropic or isotropic HFI constant) or with the angular momentum of this radical (spin rotational relaxation) and (ii) dipole dipole and exchange relaxations due to the interaction between electrons in the radicals within the RP. Methods for the description of electron relaxation in the interacting radicals are not available as yet.To date, the electron spin dynamics and relaxation of free radicals have been well studied in strong magnetic fields that much exceed typical HFI constants of organic radicals. Various experimental techniques were elaborated and detailed theoretical concepts were proposed, which makes it possible to determine the spin relaxation rates by analyzing experimental data. 8, 9 Recently, there has been increasing literature on the behavior of radicals in weak magnetic fields whose magnitude is at most equal to the HFI constants of the radicals. Spin relaxation in weak magnetic fields has long been poorly studied both experi mentally and theoretically. Experimental studies are scarce because of relatively small number of methods of measur ing the relaxation times of radicals in weak magnetic fields. L Band time resolved EPR investigations of the radicals characterized by high HFI constants (30-70 mT) allow one to obtain information on the spin relaxation of radi cals in weak and zero magnetic fields. 10,11 Because the sensitivity of c.w. EPR in weak magnetic fields is low (~10 15 spins per sample), in this case information on elec tron spin relaxation can be extracted using indirect mag netic r...

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