Anion radicals of pheophytin and chlorophyll a: their role in the primary charge separations of plant photosynthesis
| Autor: | J. Fajer, I. Fujita, M. S. Davis |
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| Rok vydání: | 1978 |
| Předmět: | |
| Zdroj: | Journal of the American Chemical Society. 100:6280-6282 |
| ISSN: | 1520-5126 0002-7863 |
| DOI: | 10.1021/ja00487a079 |
| Popis: | Redox, optical, and paramagnetic characteristics of the anion radicals of chlorophyll(Chl./sup -/) and pheophytin(pheo./sup -/) were measured. Solutions of Chl./sup -/ and Pheo./sup -/ in dimethylformamide(DMF) were prepared by controlled electrolysis of oxygen free solutions in which the solvent had been pretreated with activated molecular sieves followed by activated neutral alumina. The electrolysis reactions were reversible as one-electron oxidation of the radicals regenerated better than 90% of the original chlorins. ESR and ENDOR spectra showed no differences in samples prepared in deuterated DMF (99.5% d/sub 7/), even after prolonged standing--indicating that no significant reactions occurred with solvent protons at sites of high spin densities. A comparison of the optical changes induced by light in a Chl protein complex of photosystem II poised at -0.49 V (vs, NHE) as reported in the literature and the difference spectra obtained on reduction of Pheo and Chl in DMF is drawn. The authors conclude that the first reduced chemical products of green plant photosynthesis are the anions of pheophytin in the photosystem which oxidizes water (photosystem II), and the anions of chlorophyll in the photosystem which reduces carbon dioxide (photosystem I). 4 figures, 1 table, 39 references. |
| Databáze: | OpenAIRE |
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