Singlet oxygen-mediated photobleaching of the prosthetic group in hemoglobins and c-phycocyanin

Tapia, G; Galetovic, A; Lemp, E; Pino, E; Lissi, E


Proteins bearing colored prosthetic groups, such as the heme group in hemoglobin or the bilin group in c-phycocyanin, quench singlet oxygen by interactions at the apoprotein and the prosthetic group levels. In both proteins, chemical modification of the chromophore constitutes only a minor reaction pathway, While total deactivation of singlet oxygen takes place with rate constants of 4.0 x 10(9) and 4.2 x 10(8) M-1 s(-1) for hemoglobin and phycocyanin, respectively, the bleaching of the chromophore takes place with rate constants of 3.2 x 10(6) and similar to 1 x 10(7) M-1 s(-1). Irradiation of phycocyanin with red light bleaches the chromophore with low yields (similar to 0.8 x 10(-4)). Part of this bleaching is mediated by singlet oxygen produced by the irradiation of the bilin group. The low relevance of the singlet oxygen pathway is compatible with a low quantum yield (similar to 10(-3)) of free singlet oxygen production after irradiation of the protein.

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Título según WOS: ID WOS:000083354300007 Not found in local WOS DB
Volumen: 70
Número: 4
Editorial: Wiley
Fecha de publicación: 1999
Página de inicio: 499
Página final: 504


Notas: ISI