אסיף מאגר המחקר החקלאי

Left- and right-handed LHC II macroaggregates revealed by circularly polarized chlorophyll luminescence

Year:

2006

Source of publication :

Authors :

Volume :

87

Co-Authors:

Gussakovsky, E.E., Institute of Horticulture, ARO, Volcani Center, P.O. Box 6, Bet Dagan 50250, Israel, Faculty of Sciences, Bar Ilan University, Ramat Gan 52900, Israel, Department of Botany, University of Manitoba, Winnipeg, Man. R3T 2N2, Canada
Ionov, M.V., Sadykov Institute of Bioorganic Chemistry, Uzbekistan Academy of Sciences, Tashkent 700143, Uzbekistan
Giller, Y.E., Institute of Horticulture, ARO, Volcani Center, P.O. Box 6, Bet Dagan 50250, Israel
Ratner, K., Institute of Horticulture, ARO, Volcani Center, P.O. Box 6, Bet Dagan 50250, Israel
Aripov, T.F., Sadykov Institute of Bioorganic Chemistry, Uzbekistan Academy of Sciences, Tashkent 700143, Uzbekistan
Shahak, Y., Institute of Horticulture, ARO, Volcani Center, P.O. Box 6, Bet Dagan 50250, Israel

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Abstract:

Circularly polarized chlorophyll luminescence (CPL) may serve as a measure of chiral macroaggregates of the light-harvesting chlorophyll-protein complexes (LHC II) in both isolated chloroplasts and intact leaves (Gussakovsky et al (2000) Photosynth Res 65: 83-92). In the present work, we applied the CPL approach to study the effect of fast (1-2 min) thermal impacts on LHC II macroaggregates. The results revealed unexpected temperature-response kinetics, composed of initial bell-shaped changes in the CPL signal, followed by degradation down to a steady state (equilibrium). The bell-shape effect was dependent upon illumination, and vanished in the dark. A mathematical analysis of the temperature-response kinetics uniquely indicated that LHC II chiral macroaggregates may persist in both left- and right-handed forms. These forms differ in their response to high temperatures. Both forms are more thermostable in leaves than in isolated chloroplasts. The cooperative degradation of LHC II macroaggregates, which is induced by the thermal impact, is irreversible. It is therefore suggested that the native LHC II macroaggregates are stable, stationary, non-equilibrium, spatially heterogeneous (dissipative) structures. The dissipative properties probably allow the interconversion between left- and right-handed forms under perturbation by certain factors. Illumination probably serves as one such perturbation factor, initiating the interconversion of dark-adapted, left-handed to light-dependent, right-handed LHC II macroaggregates. The chiral heterogeneity of the LHC II macroaggregates is a newly revealed aspect which needs to be taken into consideration in future circular dichroism or CPL studies. © Springer 2006.

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