Thorsten Ritz

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A large variety of animals has the ability to sense the geomagnetic field and utilize it as a source of directional (compass) information. It is not known by which biophysical mechanism this magnetoreception is achieved. We investigate the possibility that magnetoreception involves radical-pair processes that are governed by anisotropic hyperfine coupling(More)
Migratory birds are known to use the geomagnetic field as a source of compass information. There are two competing hypotheses for the primary process underlying the avian magnetic compass, one involving magnetite, the other a magnetically sensitive chemical reaction. Here we show that oscillating magnetic fields disrupt the magnetic orientation behaviour of(More)
Cryptochromes are flavoprotein photoreceptors first identified in Arabidopsis thaliana, where they play key roles in growth and development. Subsequently identified in prokaryotes, archaea, and many eukaryotes, cryptochromes function in the animal circadian clock and are proposed as magnetoreceptors in migratory birds. Cryptochromes are closely structurally(More)
The avian magnetic compass has been well characterized in behavioral tests: it is an "inclination compass" based on the inclination of the field lines rather than on the polarity, and its operation requires short-wavelength light. The "radical pair" model suggests that these properties reflect the use of specialized photopigments in the primary process of(More)
The radical pair model of magnetoreception predicts that magnetic compass orientation can be disrupted by high frequency magnetic fields in the Megahertz range. European robins, Erithacus rubecula, were tested under monochromatic 565 nm green light in 1.315 MHz fields of 0.48 μT during spring and autumn migration, with 1.315 MHz being the frequency that(More)
Peridinin-chlorophyll-protein (PCP) is a unique light-harvesting protein that uses carotenoids as its primary light-absorbers. This paper theoretically investigates excitation transfer between carotenoids and chlorophylls in PCP of the dinoflagellate Amphidinium carterae. Calculations based on a description of the electronic states of the participating(More)
Recently, oscillating magnetic fields in the MHz-range were introduced as a useful diagnostic tool to identify the mechanism underlying magnetoreception. The effect of very weak high-frequency fields on the orientation of migratory birds indicates that the avian magnetic compass is based on a radical pair mechanism. To analyse the nature of the magnetic(More)
Cryptochromes are blue-light absorbing photoreceptors found in many organisms where they have been involved in numerous growth, developmental, and circadian responses. In Arabidopsis thaliana, two cryptochromes, CRY1 and CRY2, mediate several blue-light-dependent responses including hypocotyl growth inhibition. Our study shows that an increase in the(More)
Photosynthetic organisms fuel their metabolism with light energy and have developed for this purpose an efficient apparatus for harvesting sunlight. The atomic structure of the apparatus, as it evolved in purple bacteria, has been constructed through a combination of x-ray crystallography, electron microscopy, and modeling. The detailed structure and(More)
The excitation energy transfer between light-harvesting complex I (LH-I) and the photosynthetic reaction center (RC) of the purple bacterium Rhodobacter (Rb.) sphaeroides is investigated on the basis of the atomic level structures of the two proteins, assuming a ring-shaped model for LH-I. Rates of excitation energy transfer are calculated, based on Förster(More)