EFFECTS OF QUENCHING AGENTS ON THE PHOTODYNAMICALLY-INDUCED CHEMOTACTIC RESPONSE OF THE COLORLESS FLAGELLATE Polytomella magna |
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| Authors: | Wilhelm Nultsch Har Darshan Kumar |
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| Institution: | Botanisches Institut, Fachbereich Biologie der Philipps-Universität Marburg, Karl v. Frisch-Str., D-3550 Marburg 1, W. Germany, and Centre of Advanced Study in Botany, Banaras Hindu University, Varanasi 22 10 05, India |
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| Abstract: | Abstract In the presence of the photosensitizer riboflavin at high fluence rates a photoproduct, most probably H2O2, is formed which causes negative phototaxis in the colorless flagellate Polytomella magna . The aim of this study was to find out whether H2O2 is produced in a type I or II reaction. As has been shown, 1O2 quenchers either do not influence the photodynamic action of riboflavin (furfuryl ethanol, DPBF, l -histidine, crocetin) or show slight quenching effects only at very high concentrations ≧ 10−2 M (DABCO, DMF, imidazole). D2O is toxic to P. magna even in 1:1 and 1:2 mixtures with H2O. On the other hand, the quenching effect of 1,4-benzoquinone, highly indicative for the type I pathway, is more than two orders of magnitude stronger than the one of the above mentioned 1O2 quenchers. The results suggest that H2O2 is produced in a type I reaction. Superoxide does not seem to be involved since superoxide dismutase does not diminish the photodynamic effect of riboflavin. |
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