| 1 | Author
| P. V. Sane, T. S. Desai, V. G. Tatake | Requires cookie* | | Title
| Luminescence from Photosystem I at High Temperatures  | | | Abstract
| The changes in the fluorescence and delayed fluorescence intensity of spinach leaf as affected by temperature were studied. It was observed that the delayed fluorescence showed a maximum at about 45 °C whereas the fluorescence maximum was at about 55 °C. An examination of the emission spectra of delayed fluorescence at different temperatures showed that at higher tem peratures the relative emission at 735 nm was increased. It is argued that at higher temperatures the luminescence from photosystem I contributes to delayed fluorescence. | | |
Reference
| Z. Naturforsch. 35c, 289—292 (1980); received November 1 1979 | | |
Published
| 1980 | | |
Keywords
| Fluorescence, Delayed Fluorescence, Photosystem I | | |
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| default:Reihe_C/35/ZNC-1980-35c-0289.pdf | | | Identifier
| ZNC-1980-35c-0289 | | | Volume
| 35 | |
2 | Author
| GeoffreyA. Codd, G. Eorg, H. Schmid | Requires cookie* | | Title
| Effects of S-^^-DichlorophenyO-N-N'-Dimethylurea on Oxygen Evolution and Fluorescence by Whole Filaments and Isolated Thylakoids of the Cyanobacterium Anabaena cylindrica  | | | Abstract
| The site of inhibition of DCM U against photosystem II in the cyanobacterium (Blue-green alga) Anabaena cylindrica was examined in electron transport and fluorescence studies. Isolated thylakoids catalyzed silicomolybdate photoreduction using H zO as electron donor; the steady-state reaction was completely inhibited by DCM U. This reaction is insensitive to DCM U in chloro plasts, since silicomolybdate accepts electrons from the prim ary photosystem II acceptor, and thus before the site of action o f D CM U in higher plants. DCM U did not increase the steady-state level of fluorescence by inact A. cylindrica, nor affect the monophasic fluorescence induction, with | | |
Reference
| Z. Naturforsch. 35c, 649—655 (1980); received April 18 1980 | | |
Published
| 1980 | | |
Keywords
| Oxygen-Evolving Side, Cyanobacteria, D CM U-Sensitivity, Fluorescence | | |
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| default:Reihe_C/35/ZNC-1980-35c-0649.pdf | | | Identifier
| ZNC-1980-35c-0649 | | | Volume
| 35 | |
3 | Author
| Jacek Wierzchowski, M. Arian Szczęśniak, D. Avid Shugar | Requires cookie* | | Title
| Fluorescence Emission Properties of the Cation of 4-Aminopyrazole(3,4-d) pyrimidine, an Adenine Analogue: Evidence for Phototautomerism  | | | Abstract
| A study has been made of the emission spectra at room temperature, in aqueous and alcoholic media, of 4-aminopyrazolo(3,4-d)pyrimidine (APP) and some o f its methylated derivatives. The cationic forms APPH+, N 2-methyl-APPH+ and N 7-methyl-APPH+ exhibit intense fluorescence un der these conditions, the first two exhibiting excitation spectra which differ from the absorption spectra, pointing to the existence o f a tautomeric equilibrium in the ground state. From the shape o f the excitation spectra, and comparisons with methylated analogues in fixed tautomeric forms, it follows that the emission of APPH+ originates exclusively from the species N (2)-H ,N (7)-H +, the other forms being non-fluorescent. The proportion o f the emitting species, calculated from the ex citation wavelength dependence o f the quantum yield, is in good agreement with data for the ground state. The emission spectrum of APPH+ in aqueous medium consists o f two bands with /lmax 360 nm and 430 nm, which exhibit identical excitation spectra, but are quenched to different extents by H30 +. The 430 nm emission band is absent in alcoholic media. A similar behaviour is exhibited by N 7-methyl-APPH+, whereas the neutral form o f this analogue exhibits only the 430 nm band. These results indicate that the long wavelength emission band o f APPH+ originates from the rare tautomeric species N(7)-H formed in the excited state by photodissociation o f the N(2)-H proton from the species N(2)-H ,N(7)-H+. This is further confirmed by results obtained with the aid o f the basicity method, as well as by salt efects in non-aqueous media. Consideration is given to the possibility of such processes occurring in other analogues o f nucleic acid derivatives. | | |
Reference
| Z. Naturforsch. 35c, 878—8 (1980); received July 28 1980 | | |
Published
| 1980 | | |
Keywords
| Fluorescence, Phototautomerism, Pyrazolo(3, 4-d)pyrimidines, Adenine Analogues, Protonation Sites | | |
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| default:Reihe_C/35/ZNC-1980-35c-0878.pdf | | | Identifier
| ZNC-1980-35c-0878 | | | Volume
| 35 | |
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