Chlorophyll‐Derived Yellow Phyllobilins of Higher Plants as Medium‐Responsive Chiral Photoswitches |
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| Authors: | Dr Chengjie Li Dr Klaus Wurst Dr Steffen Jockusch Prof Karl Gruber Dr Maren Podewitz Prof Klaus R Liedl Prof Bernhard Kräutler |
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| Affiliation: | 1. Institute of Organic Chemistry and Centre of Molecular Biosciences, University of Innsbruck, Innsbruck, Austria;2. Institute of General, Inorganic & Theoretical Chemistry, University of Innsbruck, Austria;3. Department of Chemistry, Columbia University, New York, USA;4. Institute of Molecular Biosciences, University of Graz, Austria;5. Institute of General, Inorganic & Theoretical Chemistry and Centre of Molecular Biosciences, University of Innsbruck, Austria |
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| Abstract: | The fall colors are signs of chlorophyll breakdown, the biological process in plants that generates phyllobilins. Most of the abundant natural phyllobilins are colorless, but yellow phyllobilins (phylloxanthobilins) also occur in fall leaves. As shown here, phylloxanthobilins are unique four‐stage photoswitches. Which switching mode is turned on is controlled by the molecular environment. In polar media, phylloxanthobilins are monomeric and undergo photoreversible Z/E isomerization, similar to that observed for bilirubin. Unlike bilirubin, however, the phylloxanthobilin Z isomers photodimerize in apolar solvents by regio‐ and stereospecific thermoreversible 2+2] cycloadditions from self‐assembled hydrogen‐bonded dimers. X‐ray analysis revealed the first stereostructure of a phylloxanthobilin and its hydrogen‐bonded self‐templating architecture, helping to rationalize its exceptional photoswitch features. The chemical behavior of phylloxanthobilins will play a seminal role in identifying biological roles of phyllobilins. |
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| Keywords: | cycloaddition hydrogen bonds photoisomerization plant pigments self-assembly |
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