Correlation of electronic carotenoid–chlorophyll interactions and fluorescence quenching with the aggregation of native LHC II and chlorophyll deficient mutants

Abstract

a b s t r a c tThe aggregation dependent correlation between fluorescence quenching and the electronic carotenoidchlorophyll interactions, / Car S 1 ÀChl Coupling , as measured by comparing chlorophyll fluorescence observed after two-and one-photon excitation, has been investigated using native LHC II samples as well as mutants lacking Chl 2 and Chl 13. For native LHC II the same linear correlation between / Car S 1 ÀChl Coupling and the fluorescence quenching was observed as previously reported for the pH and Zea-dependent quenching of LHC II [1]. In order to elucidate which carotenoid-chlorophyll pair might dominate this correlation we also investigated the mutants lacking Chl 2 and Chl 13. However, also with these mutants the same linear correlation as for native LHC II was observed. This provides indication that these two chlorophylls play only a minor role for the observed effects. Nevertheless, we also conclude that this does not exclude that their neighboured carotenoids, lutein 1 and neoxanthin, might interact electronically with other chlorophylls close by.

Carotenoid–Chlorophyll Coupling and Fluorescence Quenching Correlate with Protein Packing Density in Grana-Thylakoids

“…In addition, Figure 4 shows that the coupling of isolated LHCII complexes decreases correspondingly with decreasing aggregation and quenching, as previously observed. 27 For a quantitative comparison of the couplings observed in LHCII with those in diluted grana membranes, all data were normalized to the corresponding F OPE value of unquenched LHCII ( Figure 4, Table 1). For high F OPE values, this comparison provides evidence that the electronic coupling in grana membranes is lower (lower Φ coupling ) than in pure LHCII.…”

“…6,10,26 Additionally, it was found that aggregation of LHCII trimers in vitro also causes an increase of the abovementioned coupling parameter. 27 However, it is difficult to assess how much isolated LHCII and models of aggregation quenching really reflect the in vivo situation. A much better approach to gain insight into the influence of the protein packing density in thylakoid membranes is varying the packing density in native grana thylakoids by fusion with liposomes harboring a lipid composition of natural thylakoids.…”

Correlation of Car S1 → Chl with Chl → Car S1 Energy Transfer Supports the Excitonic Model in Quenched Light Harvesting Complex II

“…Figure 3 shows that we observed the same linear correlation between φ Coupling CarS 1 -Chl and NPQ as in our previous report. 17 In Figure 2b, the corresponding absorption spectra of LHCII in different quenched states are shown along with the corresponding absorption difference spectra calculated by subtracting the spectrum of the unquenched LHCII from the spectra of the quenched LHCII samples. In the absorption difference spectra, thesamered-shiftedbandsareobservedasdescribedpreviously.…”

“…17 The detection of fluorescence from the Chl a Q y states upon selective two-photon excitation (Fl TPE ) of the carotenoid dark states, Car S 1 , provides direct evidence for electronic interactions between Car S 1 and Chl Q y states. Therefore, this experiment reflects the energy flow in the direction Car S 1 f Chl a.…”

“…In our previous work, we observed a simultaneously increased energy transfer in the direction Car S 1 f Chl Q y in down-regulated living plants as well as in aggregated LHCII. 14,17 Energy transfer and excitonic interactions are both governed by the same electronic interactions. If the energies of both participating pigments are significantly different, then electronic interactions lead to energy transfer to the energetically lower state, i.e., either in the direction Car S 1 f Chl Q y (Figure 1 A) or in the direction Chl f Car S 1 (Figure 1 B).…”