| | 1 | Author
| M. D. Arie-Jose, Elrieu | Requires cookie* | | | Title
| The Effects of 3-(3,4-Dichlorophenyl)-l,l-dimethylurea on the Photosynthetic Oxygen Complex  | | | | Abstract
| In the presence o f trypsin and ferricyanide as external electron acceptor, lettuce chloroplasts are resistant to DCM U, showing that the inhibitory site o f D C M U is only situated on the accep tor side o f photosystem II. However, kinetic properties o f the oxygen evolving com plex are m od i fied at non-saturating concentrations o f D C M U . These changes are interpreted in terms o f a model with two distinct charges separation systems on the sam e center: the auxiliary donor-acceptor system D Q L implicated in the transitions S| -» • S 2 and S2 -*■ S 3 would be m uch less affected by DCM U than the main donor-acceptor system Y Q H after the first flash. | | | |
Reference
| Z. Naturforsch. 39c, 347—350 (1984); received N ovem ber 28 1983 | | | |
Published
| 1984 | | | |
Keywords
| Herbicides, Oxygen Evolution, Photosystem II, Electron Acceptors, Electron D onors | | | |
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| default:Reihe_C/39/ZNC-1984-39c-0347.pdf | | | | Identifier
| ZNC-1984-39c-0347 | | | | Volume
| 39 | |
| 2 | Author
| Marie-Jose Delrieu | Requires cookie* | | | Title
| Evidence for Unequal M isses in Oxygen Flash Yield Sequence in Photosynthesis | | | | Abstract
| The numerical analysis of the oxygen flash yield Yn sequences, alone, does not allow to choose between two models: equal S state misses with non negligible double hits or unequal misses with nearly no double hits. Nevertheless, the com parison o f the sequences in different conditions shows that the equal miss model is unrealistic: in very different experimental conditions (non saturating flash, different batch o f Chlorella or chloroplasts), a parallel variation of the hom o geneous miss and double hit factors is observed. This correlation seems strange within the equal miss model: misses come from incomplete reaction (i.e. for exemple insufficient light) and double hits i.e. double advancem ent come, in principle, from excessive light or too long flash; for these reasons, opposite variation of misses and double hits as a function of light intensity are ex pected. W ithin the equal miss model the inverse is exactly observed: at low flash light intensity (11%) which increases the misses, 16% of double hits are needed, which is quite unrealistic. In contrast, the unequal miss model explains such result quite naturally by a m athem atical property: any theoretical sequence with only a unique S state miss and no double hit can be fitted with homogeneous misses and double hits, which increase in parallel as a function o f the damping. Evidence for unequal misses in oxygen flash yield sequence is provided by the heterogeneous properties of the light saturation curves (M. J. D elrieu, Biochim. Biophys. Acta 592, 4 7 8 -4 9 4 (1980)). At high flash intensity, all, excepted the transition S ' 2 -*■ S3 , are saturated; the transition £ 2 -* S3 is far from saturation and its very large saturating light intensity is actually not known. A comparative study, in the same chloroplast batch, o f the oxygen yield patterns with attenuated flashes and of the experimental saturation curves of S states shows that only photo chemical misses (due to non saturation) exist. At high intensity, there is only a unique miss for the transition S 2 S 3 i.e. the probability for this transition is low. A model involving a second acceptor could explain the slow increase of transition probability o f S ' 2 -* S3 at high flash intensity. | | | |
Reference
| Z. Naturforsch. 38c, 247—258 (1983); received N ovem ber 16 1982 | | | |
Published
| 1983 | | | |
Keywords
| Oxygen Evolution, Photosystem II, M atrix Analysis, N on Saturating Flash Sequence, Electron Acceptor | | | |
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| default:Reihe_C/38/ZNC-1983-38c-0247.pdf | | | | Identifier
| ZNC-1983-38c-0247 | | | | Volume
| 38 | |
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