Characterization of Low-Energy Chlorophylls in the PSI-LHCI Supercomplex from Chlamydomonas reinhardtii. A Site-Selective Fluorescence Study

Abstract

Almost all photosystem I (PSI) complexes from oxygenic photosynthetic organisms contain chlorophylls that absorb at longer wavelength than that of the primary electron donor P700. We demonstrate here that the low-energy pool of chlorophylls in the PSI-LHCI complex from the green alga Chlamydomonas reinhardtii, containing five to six pigments, is significantly blue-shifted (A max at 700 nm at 4 K) compared to that in the PSI core preparations from several species of cyanobacteria and in PSI-LHCI particles from higher plants. This makes them almost isoenergetic with the primary donor. However, they keep the other characteristic features of "red" chlorophylls: clear spectral separation from the bulk chlorophylls, big Stokes shift revealing pronounced electron-phonon coupling, and large homogeneous and inhomogeneous broadening of ∼170 and ∼310 cm -1 , respectively.

Generality of relationships between leaf pigment contents and spectral vegetation indices in Mallorca (Spain)

“…However, the spectral region which proved to be the best predictor of Chl a and other pigments was located at much longer wavelengths than PSI reaction center absorption at 700 nm. Mechanistically, light should be absorbed in this spectral region by the small number of specific pigmentprotein complexes, so called Bfar-red chlorophylls^ (Gobets and van Grondelle 2001;Melkozernov 2001;Gibasiewicz et al 2005), which nevertheless could transfer light energy to both PSII and PSI (Oja et al 2004;Pettai et al 2005a,b). The existence of such pigments has been shown and Fig.…”

Fluorescence hole-burning and site-selective studies of LHCII

“…The concentrated sample was diluted before the fluorescence experiments in a buffer containing 20 mM Bis Tris (pH = 6.0), 10 mM NaCl, Methods: A diluted sample (OD 676nm,10mm ≈ 0.1) was placed in a (10 mm × 10 mm plastic) cuvette and frozen to 4.2 K in a liquid helium cryostat (Utreks; Kiev, Ukraine). Both FHB and SSF experiments were performed with the setup described previously (Gibasiewicz et al 2005). Shortly, the source of the nonselective excitation at 420 nm in the FHB experiment was a 150-W tungsten halogen lamp equipped with an interference filter (fwhm = 20 nm).…”

“…A technique complementary to AHB, also wellestablished, is the fluorescence line narrowing (FLN; Peterman 1998, Pieper et al 2001, Timpmann et al 2004, Gibasiewicz et al 2005, Rätsep et al 2005. In photosynthetic complexes, low temperature emission originates from a distribution of the lowest-energy states.…”

The Interplay of Light and Oxygen in the Reactive Oxygen Stress Response of Chlamydomonas reinhardtii Dissected by Quantitative Mass Spectrometry

“…This particular asparagine is however absence in the LHCA3 homolog of C. reinhardtii. In fact, Gibasiewicz et al (118) showed that C. reinhardtii contains a special set of low-energy chlorophylls that are iso-energenic with the primary donor of PSI, yet retain some of the red chlorophyll characteristics. Furthermore the locations of the "far red like" chlorophylls still need to be identified.…”