THE BLUE ANOMALOUS EMISSION OF LARGE AND SMALL PHYTOCHROME*

Abstract

Abstract –Small and immunoaffinity‐purified large phytochrome (P r and P fr ) show a so‐called anomalous fluorescence with λ em max = 470 and 440 nm, respectively, when irradiated within the blue absorption band. Model studies indicate that this emission arises from a dipyrromethenone partial structure produced by a nucleophilic addition to the central carbon C‐10 of the bilindione chromophore. The anomalous emitter of phytochrome is thus similar to one bilirubin conformer which has previously been found to contribute to the absorption and emission of the bile pigment.