TYROSINE Y-Z AND Y-D OF PHOTOSYSTEM-II - COMPARISON OF OPTICAL-SPECTRA TO THOSE OF TYROSINE OXIDIZED BY PULSED RADIOLYSIS

We have compared the optical spectrum of tyrosine oxidised in aqueous solution by pulsed radiolysis with spectra of redox active tyrosines Y -Z and Y-D of photosystem II. This indicates a ''tyrosinate'' state fo r these tyrosines and also casts doubt on the assumption that Y-Z and Y-D optical spectra are very similar in different photosystem II prepa rations. It suggests that further optical spectra of Y-Z in more intac t oxygen-evolving preparations are needed before the role of Y-z in wa ter oxidation can be clarified. (C) 1998 Elsevier Science B.V.