scholarly journals Light-dependent magnetoreception in birds: the crucial step occurs in the dark

2016 ◽  
Vol 13 (118) ◽  
pp. 20151010 ◽  
Author(s):  
Roswitha Wiltschko ◽  
Margaret Ahmad ◽  
Christine Nießner ◽  
Dennis Gehring ◽  
Wolfgang Wiltschko
Keyword(s):  
Magnetic Field ◽  
Flavin Adenine Dinucleotide ◽  
Radical Pair ◽  
Magnetic Compass ◽  
Radical Pairs ◽  
Intermittent Light ◽  
Pair Model ◽  
Dark Interval ◽  
Behavioural Experiments ◽  
The Magnetic Field

The Radical Pair Model proposes that the avian magnetic compass is based on spin-chemical processes: since the ratio between the two spin states singlet and triplet of radical pairs depends on their alignment in the magnetic field, it can provide information on magnetic directions. Cryptochromes, blue light-absorbing flavoproteins, with flavin adenine dinucleotide as chromophore, are suggested as molecules forming the radical pairs underlying magnetoreception. When activated by light, cryptochromes undergo a redox cycle, in the course of which radical pairs are generated during photo-reduction as well as during light-independent re-oxidation. This raised the question as to which radical pair is crucial for mediating magnetic directions. Here, we present the results from behavioural experiments with intermittent light and magnetic field pulses that clearly show that magnetoreception is possible in the dark interval, pointing to the radical pair formed during flavin re-oxidation. This differs from the mechanism considered for cryptochrome signalling the presence of light and rules out most current models of an avian magnetic compass based on the radical pair generated during photo-reduction. Using the radical pair formed during re-oxidation may represent a specific adaptation of the avian magnetic compass.

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 Very weak oscillating magnetic field disrupts the magnetic compass of songbird migrants

2017 ◽  
Vol 14 (133) ◽  
pp. 20170364 ◽  
Author(s):  
Alexander Pakhomov ◽  
Julia Bojarinova ◽  
Roman Cherbunin ◽  
Raisa Chetverikova ◽  
Philipp S. Grigoryev ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Narrow Band ◽  
Radical Pair ◽  
Magnetic Compass ◽  
Sensitivity Threshold ◽  
Erithacus Rubecula ◽  
Long Distance ◽  
Pair Model ◽  
Oscillating Magnetic Field ◽  
Sylvia Borin

Previously, it has been shown that long-distance migrants, garden warblers ( Sylvia borin ), were disoriented in the presence of narrow-band oscillating magnetic field (1.403 MHz OMF, 190 nT) during autumn migration. This agrees with the data of previous experiments with European robins ( Erithacus rubecula ). In this study, we report the results of experiments with garden warblers tested under a 1.403 MHz OMF with various amplitudes (∼0.4, 1, ∼2.4, 7 and 20 nT). We found that the ability of garden warblers to orient in round arenas using the magnetic compass could be disrupted by a very weak oscillating field, such as an approximate 2.4, 7 and 20 nT OMF, but not by an OMF with an approximate 0.4 nT amplitude. The results of the present study indicate that the sensitivity threshold of the magnetic compass to the OMF lies around 2–3 nT, while in experiments with European robins the birds were disoriented in a 15 nT OMF but could choose the appropriate migratory direction when a 5 nT OMF was added to the stationary magnetic field. The radical-pair model, one of the mainstream theories of avian magnetoreception, cannot explain the sensitivity to such a low-intensity OMF, and therefore, it needs further refinement.

scholarly journals Polarized light modulates light-dependent magnetic compass orientation in birds

2016 ◽  
Vol 113 (6) ◽  
pp. 1654-1659 ◽  
Author(s):  
Rachel Muheim ◽  
Sissel Sjöberg ◽  
Atticus Pinzon-Rodriguez
Keyword(s):  
Magnetic Field ◽  
Radical Pair ◽  
Polarized Light ◽  
Magnetic Compass ◽  
Radical Pair Mechanism ◽  
Magnetic Field Effects ◽  
Compass Orientation ◽  
Magnetic Compass Orientation ◽  
Avian Retina ◽  
The Magnetic Field

Magnetoreception of the light-dependent magnetic compass in birds is suggested to be mediated by a radical-pair mechanism taking place in the avian retina. Biophysical models on magnetic field effects on radical pairs generally assume that the light activating the magnetoreceptor molecules is nondirectional and unpolarized, and that light absorption is isotropic. However, natural skylight enters the avian retina unidirectionally, through the cornea and the lens, and is often partially polarized. In addition, cryptochromes, the putative magnetoreceptor molecules, absorb light anisotropically, i.e., they preferentially absorb light of a specific direction and polarization, implying that the light-dependent magnetic compass is intrinsically polarization sensitive. To test putative interactions between the avian magnetic compass and polarized light, we developed a spatial orientation assay and trained zebra finches to magnetic and/or overhead polarized light cues in a four-arm “plus” maze. The birds did not use overhead polarized light near the zenith for sky compass orientation. Instead, overhead polarized light modulated light-dependent magnetic compass orientation, i.e., how the birds perceive the magnetic field. Birds were well oriented when tested with the polarized light axis aligned parallel to the magnetic field. When the polarized light axis was aligned perpendicular to the magnetic field, the birds became disoriented. These findings are the first behavioral evidence to our knowledge for a direct interaction between polarized light and the light-dependent magnetic compass in an animal. They reveal a fundamentally new property of the radical pair-based magnetoreceptor with key implications for how birds and other animals perceive the Earth’s magnetic field.

scholarly journals Compass magnetoreception in birds arising from photo-induced radical pairs in rotationally disordered cryptochromes

2012 ◽  
Vol 9 (77) ◽  
pp. 3329-3337 ◽  
Author(s):  
Jason C. S. Lau ◽  
Christopher T. Rodgers ◽  
P. J. Hore
Keyword(s):  
Theoretical Analysis ◽  
Geomagnetic Field ◽  
Migratory Birds ◽  
Radical Pair ◽  
Current Model ◽  
Magnetic Compass ◽  
Radical Pairs ◽  
Molecular Precursors ◽  
Pair Model ◽  
Photochemical Transformations

According to the radical pair model, the magnetic compass sense of migratory birds relies on photochemical transformations in the eye to detect the direction of the geomagnetic field. Magnetically sensitive radical pairs are thought to be generated in cryptochrome proteins contained in magnetoreceptor cells in the retina. A prerequisite of the current model is for some degree of rotational ordering of both the cryptochromes within the cells and of the cells within the retina so that the directional responses of individual molecules do not average to zero. Here, it is argued that anisotropic distributions of radical pairs can be generated by the photoselection effects that arise from the directionality of the light entering the eye. Light-induced rotational order among the transient radical pairs rather than intrinsic ordering of their molecular precursors is seen as the fundamental condition for a magnetoreceptor cell to exhibit an anisotropic response. A theoretical analysis shows that a viable compass magnetoreceptor could result from randomly oriented cryptochromes contained in randomly oriented cells distributed around the retina.

Chemically Induced Dynamic Nuclear Polarization. X. On Effects of Nuclear Relaxation and the Magnetic Field Dependence

1972 ◽  
Vol 27 (8-9) ◽  
pp. 1300-1307 ◽  
Author(s):  
M. Lehnig ◽  
H Fischer
Keyword(s):  
Magnetic Field ◽  
Field Dependence ◽  
Magnetic Field Dependence ◽  
Nuclear Polarization ◽  
Radical Pair ◽  
Reaction Products ◽  
Theory Analysis ◽  
Alkyl Radicals ◽  
Chemically Induced ◽  
The Magnetic Field

Abstract The magnetic field dependence of CIDNP is presented for two reaction products of independently generated alkyl radicals. It is shown that nuclear spin relaxation of the products influences the intensity distributions within multiplets, and how this relaxation can be included in the calculation of CIDNP effects from the radical pair theory. Analysis of the experimental results supports the recent view that CIDNP is created in pairs of radicals which undergo many diffusive displacements before reencounter.

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.

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