Chemiluminescence in the reaction of cytochrome c with hydrogen peroxide |
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Authors: | J Slawinski W Galezowski M Elbanowski |
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Institution: | 1. Institute of Physics and Chemistry, Academy of Agriculture, Wojska Polskiego 38/42, 60–637 Pozna''nPoland;2. Institute of Chemistry, Pozna''n University, Grunwaldzka 6, 60–780 Pozna''nPoland |
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Abstract: | (1) Aqueous solutions of 1–10 μM ferricytochrome c treated with 100 μM–100 mM H2O2 at pH 8.0 emit chemiluminescence with quantum yield and absolute maximum intensity per cm3 (λ = 440), and exhibit exponential decay with a rate constant of 0.15 s?1. (2) The emission spectrum of the chemiluminescence covers the range 380–620 nm with the maximum at 460 ± 10 nm. (3) Neither cytochrome c nor haemin fluoresce in the spectral region of the chemiluminescence. In the reaction course with H2O2, a weak fluorescence in the region 400–620 nm with λmax = 465–510 nm (λexc 315–430 nm) gradually arises. This originates from tryptophan oxidation products of the formylkynurenine type or from imidazole derivatives, respectively. (4) Frozen solutions (77 K) of cytochrome c exhibit phosphorescence typical of tryptophan (λexc = 280 nm, λem = 450 nm). During the peroxidation, an additional phosphorescence gradually appears in the range 480–620 nm with λmax = 530 nm (λexc = 340 nm). This originates from oxidative degradation products of tryptophan. (5) There are no red bands in the chemiluminescence spectra of cytochrome c or haemin. This result suggests that singlet molecular oxygen is not involved in either peroxidation or chemiluminescence. (6) The haem Fe3+ group and H2O2 appear to be crucial for the chemiluminescence. It is suggested that the generation of electronically excited, light-emitting states is coupled to the production of conformational out-of-equilibrium states of peroxy-Fe-protoporphyrin IX compounds. |
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Keywords: | Chemiluminescence Singlet oxygen Hydrogen peroxide |
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