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Steady-state and time-resolved polarized light spectroscopy of the green plant light-harvesting complex II

1992; Elsevier BV; Volume: 1101; Issue: 2 Linguagem: Inglês

10.1016/0005-2728(92)90198-b

1879-2650

Stefan L.S. Kwa, F.G. Groeneveld, Jan P. Dekker, Rienk van Grondelle, Herbert van Amerongen, S.H. Lin, Walter S. Struve,

Photoreceptor and optogenetics research

Abstract The major chlorophyll a/b light-harvesting complex from spinach thylakoid membranes was analyzed by steady-state polarized light spectroscopy at 4 K and by one-color and two-color pump-probe spectroscopy at room temperature. Steady-state absorption, linear dichroism and circular dichroism spectra indicate that the Chl Q y (0−0) absorption region is characterized by at least six transitions with significant differences in absorption, orientation and rotational strength. Steady-state low-temperature fluorescence spectra suggest that the fluorescence arises for a large part from several energetically similar species that form a circularly degenerate oscillator in the plane constituted by the two long axes of the particle. The possible presence of special red-absorbing pigments at low temperature is discussed. The time-resolved data suggest that the kinetics of chlorophyllb → a excitation energy transfer, as well as those of downhill excitation transfer among chlorophylla spectral forms, are heterogeneous with both sub-picosecond and picosecond lifetime components.