The involvement of phycocyanin pigment in the photodecomposition of the cyanobacterial toxin, microcystin-LR

While investigating the destruction of the cyanobacterial hepatotoxin micro cystin-LR in the presence of phycocyanin pigment via semiconductor photocat alysis, it became apparent that the pigment was catalysing the toxin decomp osition. The mechanism of this process in terms of phycocyanin acting as a photo-oxygenation sensitizer via singlet oxygen and superoxide attack is ex plored. The absorption and fluorescence spectra of phycocyanin have been ob tained and data on the properties of the excited state calculated. The esta blished photo-oxygenation sensitizer rose bengal was also used as a catalys t for the photolytic decomposition of microcystin-LR to help elucidate the decomposition mechanism. Copyright (C) 1999 John Wiley & Sons, Ltd.