Fluorescence Decay Kinetics of Solubilized Pigment Protein Complexes from the Distal, Proximal, and Core Antenna of Photosystem II in the Range of 10−277 K and Absence or Presence of Sucrose

Abstract

The decay kinetics of chlorophyll (Chl) fluorescence of solubilized pigment protein complexes of the distal, proximal, and core antenna of photosystem II from higher plants have been analyzed in the temperature range of 10−277 K using buffer solutions containing or lacking sucrose as cryoprotectant. It was found that (i) at 277 K the 1Chl* decay of the complexes LHCIIb (distal), CP29 (proximal), and CP47 (core) is characterized by a biphasic kinetics with characteristic lifetimes in the range of 1.5−2.5 ns (fast phase) and 4−4.8 ns (slow phase), (ii) the slow phase dominates in all three complexes with normalized amplitudes of ≥0.65, (iii) in solutions containing sucrose the lifetime of the slow phase increases with decreasing temperature and reaches values in the range of 5.2−5.8 ns at 10 K, whereas those of the fast phase exhibit a more complex temperature dependence with a pronounced minimum value in the range of 150−200 K, (iv) markedly different temperature dependencies with pronounced minima in the range of 150−200 K are observed for both lifetime and normalized amplitude of the slow phase when the pigment protein complexes are dissolved in buffers without sucrose. The results are interpreted as evidence for two spectroscopically and kinetically distinguishable subpopulations in solubilized LHCIIb, CP29, and CP47 that are characterized by different rate constants of radiationless decay into the ground state of Chl. Possible mechanisms are discussed.

Reconstituted CP29: multicomponent fluorescence decay from an optically homogeneous sample

“…Detailed analysis of sample optical homogeneity/ heterogeneity requires the spectral resolution of steadystate measurements. These time resolved data are, in general terms, similar to previously reported measurements of this kind on CP29 (Moya et al 2001;Crimi et al 2001;Huyer et al 2004) which also show two dominant long lifetime decays as well as a minor fast decaying component. This minor, short lifetime, decay is unexpected in an isolated antenna complex and, to date, its physical origins are not properly understood.…”

“…Ahn et al 2008;Avenson et al 2008), it is worth noticing that the fluorescence decay remains multiexponential even in complexes reconstituted either in the presence of only violaxanthin or zeaxanthin . Also, as pointed out in the Introduction, the fluorescence decay is multiexponential also in the antenna core complex CP47 (Huyer et al 2004), that does not bind xanthophylls. Thus, it is difficult to think that differences in the carotenoid content, per se, could account significantly for the heterogeneity observed in the fluorescence lifetime analysis of this study and several others in the literature (e.g.…”

“…Crimi et al 2001;Pascal et al 2005;Avenson et al 2008;Johnson et al 2009;Passarini et al 2010). This suggestions is however not applicable to the multicomponent decay of CP47 (Huyer et al 2004) as this complex does not bind zeaxanthin (Alfonso et al 1994). This point has in fact already been made by Huyer et al (2004), who suggested that a dynamic equilibrium may exist between chlorophyll-protein complex conformers in which at least one chlorophyll has a modified fluorescence yield, due to differences in non-radiative decay.…”

“…Gruszecki et al1997;Moya et al 2001;Crimi et al 2001;Huyer et al 2004;Avenson et al 2008;Passarini et al 2010). An intriguing feature of all these studies is that the decay is multiexponential.…”

Parameters of the Protein Energy Landscapes of Several Light-Harvesting Complexes Probed via Spectral Hole Growth Kinetics Measurements

“…One should note, however, that changes in the parameters of the lowest-state SDF may result in some changes of the parameters of the electron-phonon coupling in order to produce the same delta-FLN spectra as reported in 17 . 4.8 ns lifetime of the lowest state was assumed 56 .…”