The influence of reducing the chlorophyll concentration by photobleaching on the relative excitation-energy-transfer rates to the artificial quinone trap dibromothymoquinone was examined in both a Photosystem II-grana preparation and the isolated lightharvesting chlorophyll a/b protein complex. Energy transfer as a function of decreasing chlorophyll was biphasic. Photobleaching of up to 30% of the total chlorophyll produced no detectable decrease in the energy-transfer rate. For photobleaching in excess of 30% the transfer rate decreased as a linear function which extrapolates to zero at 100% photobleaching, in agreement with a diffusive Forster-type transfer model in a bidimensional pigment matrix (Rubin, L.B., Braginskaya, O.V., Isakova, M.L. and Efremov, N.A. (1985) Photochem. Photobiol. 42, 77-87). The initial photobleaching-insensitive phase may therefore suggest that in the non-bleached antenna systems energy transfer could have a significant non-Förster component. It is also concluded that the physiological effects of photobleaching on photosynthetic activity via a reduced energy transfer efficiency are not likely to be significant. © 1989 Elsevier Science Publishers B.V. (Biomedical Division).
The influence of reducing the chlorophyll concentration by photobleaching on energy transfer to artificial traps within Photosystem II antenna systems
Zucchelli Giuseppe;
1989
Abstract
The influence of reducing the chlorophyll concentration by photobleaching on the relative excitation-energy-transfer rates to the artificial quinone trap dibromothymoquinone was examined in both a Photosystem II-grana preparation and the isolated lightharvesting chlorophyll a/b protein complex. Energy transfer as a function of decreasing chlorophyll was biphasic. Photobleaching of up to 30% of the total chlorophyll produced no detectable decrease in the energy-transfer rate. For photobleaching in excess of 30% the transfer rate decreased as a linear function which extrapolates to zero at 100% photobleaching, in agreement with a diffusive Forster-type transfer model in a bidimensional pigment matrix (Rubin, L.B., Braginskaya, O.V., Isakova, M.L. and Efremov, N.A. (1985) Photochem. Photobiol. 42, 77-87). The initial photobleaching-insensitive phase may therefore suggest that in the non-bleached antenna systems energy transfer could have a significant non-Förster component. It is also concluded that the physiological effects of photobleaching on photosynthetic activity via a reduced energy transfer efficiency are not likely to be significant. © 1989 Elsevier Science Publishers B.V. (Biomedical Division).I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
