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STUDIES ON PLANT BILE PIGMENTS—9. PHOTOOXIDATION OF A‐DIHYDROBILINDIONE AS PHYTOCHROME MODEL IN ACID MEDIUM
Author(s) -
Krauss C.,
Scheer H.
Publication year - 1981
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1981.tb09013.x
Subject(s) - phytochrome , bile pigments , pigment , chemistry , bile acid , biochemistry , biophysics , botany , biology , red light , organic chemistry
— The photooxidation of octaethyl‐2, 3‐dihydrobilindione ( 2 ) as a model for the P r ‐chromophore has been studied in acidic methanol. When 2 is titrated with HCl to the cation and irradiated under N 2 with an excess of I 2 , violin and rhodin type pigments are formed bearing methoxy‐substituents at either C‐4,5 or C‐15,16, respectively. The reaction is slowed down as compared to neutral conditions, it is no longer regioselective at the C‐5 methine bridge, and the formation of dimers is suppressed. From the data of this and earlier chemical model studies on the photooxidation of 2 , and the known properties of phytochrome, a reaction for the P r → P fr phototransformation is suggested, in which the chromophore is attacked by the protein moiety in a sequence of oxidation and nucleophilic substitution, which may lead to a primary redox signal for the physiological response.