Circular dichroism of phytochrome intermediates |
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Authors: | Petra H Eilfeld Peter G Eilfeld |
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Institution: | Botanisches Institut der Universität München, Menzingerstr. 67, D-8000 München 19, FRG |
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Abstract: | Phototransformation Pt to Pfr was investigated with 124-kDa phytochrome from etiolated oat seedlings ( Avena sativa L. cv. Pirol) using circular dichroism spectroscopy at -110°C to +30°C. Using absorption spectra of the intermediates formed at the respective temperatures, circular dichroism spectra (300–800 nm) of pure intermediates were calculated. The sign of the circular dichroic absorption bands changed upon formation of lumi-R, the primary photoproduct of Pr. This would be compatible with a Z→E isomerization taking place at this reaction step. The subsequent intermediates (meta-Ra and meta-Rc) as well as Pfr showed only small circular dichroism. Their absorption spectra were drastically shifted, but had similar spectral shapes. The results are discussed in terms of conformational changes of the phytochrome chromophore presumably taking place at the early steps of phototransformation Pr to Pfr. |
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Keywords: | Avena sativa low temperature spectroscopy oat phototransformation 124-kDa phytochrome rotational strength |
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