POLYVINYLPYRROLIDONE SIMULATES MEMBRANE-BINDING OF PHYTOCHROME

Polyvinylpyrrolidone (PVP) is used for the final purification of phyto chrome. If not all traces of PVP are carefully removed the photophysic al behaviour of phytochrome can be influenced. The maximum of fluoresc ence emission at 153 K is shifted by PVP from 686 nm to 680-682 nm. Ab sorption measurements show that PVP completely blocks the normal photo transformation Pr-->lumi-R at this temperature. The same behaviour has been described for <membrane>-bound phytochrome in plants. We conclud e that PVP can simulate <<membrane>>-binding of phytochrome.