Intermolecular interactions and photogeneration of free radicals in metal-free tetrasulphophthalocyanine-tryptophan systems.
Complex formation between free-base tetrasulphophthalocyanine (TSPC) and tryptophan (Trp) in solutions of high dielectric constant was studied using absorption/emission spectroscopy. ESR experiments demonstrated dye/substrate electron or hydrogen atom transfer reactions during illumination, competing with superoxide radical generation. To discriminate between the well-known Trp photodynamic (1O2 mediated) oxidation and other reactions, Fe(III)-EDTA was added to initiate the Haber-Weiss reaction. The TSPC/Trp complex showed an enhanced ability to reduce Fe(III)-EDTA. Spin-trapping experiments and the SOD and catalase-independent formation of 2-deoxyribose/thiobarbituric acid products imply involvement of a photoinduced Haber-Weiss reaction with generation of Trp-peroxyl and Trp-alkoxy radicals as intermediates, followed by formation of Trp carbon-centred radical(s).
Gantchev
T G
TG
Research Group in Cellular and Molecular Biology of Cancer, Bulgarian Medical Academy, Sofia.
Kaltchev
M G
MG
Gotchev
G P
GP
D005609:Free Radicals; D007211:Indoles; D008027:Light; D014364:Tryptophan
D005609:Free Radicals; D007211:Indoles; C028418:tetrasulfophthalocyanine; D014364:Tryptophan