TY - JOUR A1 - Betke, Alexander A1 - Lokstein, Heiko T1 - Two-photon excitation spectroscopy of photosynthetic light-harvesting complexes and pigments JF - Faraday discussions N2 - In addition to (bacterio)chlorophylls, (B)Chls, light-harvesting complexes (LHCs) bind carotenoids, and/or their oxygen derivatives, xanthophylls. Xanthophylls/carotenoids have pivotal functions in LHCs: in stabilization of the structure, as accessory light-harvesting pigments and, probably most importantly, in photoprotection. Xanthophylls are assumed to be involved in the not yet fully understood mechanism of energy-dependent (qE) non-photochemical quenching of Chl fluorescence (NPQ) in higher plants and algae. The so called "xanthophyll cycle" appears to be crucial in this regard. The molecular mechanism(s) of xanthophyll involvement in qE/NPQ have not been established, yet. Moreover, excitation energy transfer (EET) processes involving carotenoids are also difficult to study, due to the fact that transitions between the ground state (S-0, 1(1)A(g)(-)) and the lowest excited singlet state (S-1, 2(1)A(g)(-)) of carotenoids are optically one-photon forbidden ("dark"). Two-photon excitation spectroscopic techniques have been used for more than two decades to study one-photon forbidden states of carotenoids. In the current study, two-photon excitation profiles of LHCII samples containing different xanthophyll complements were measured in the presumed 1(1)A(g)(-) -> 2(1)A(g)(-) (S-0 -> S-1) transition spectral region of the xanthophylls, as well as for isolated chlorophylls a and b in solution. The results indicate that direct two-photon excitation of Chls in this spectral region is dominant over that by xanthophylls. Implications of the results for proposed mechanism(s) of qE/NPQ will be discussed. Y1 - 2019 U6 - https://doi.org/10.1039/c8fd00198g SN - 1359-6640 SN - 1364-5498 VL - 216 SP - 494 EP - 506 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Gruszecki, Wieslaw I. A1 - Stiel, H. A1 - Niedzwiedzki, Dariusz A1 - Beck, Michael A1 - Milanowska, J. A1 - Lokstein, Heiko A1 - Leupold, Dieter T1 - Towards elucidating the energy of the first excited singlet state of xanthophyll cycle pigments investigated by x-ray absorption spectroscopy Y1 - 2005 ER - TY - JOUR A1 - Leupold, Dieter A1 - Teuchner, Klaus A1 - Ehlert, Jürgen A1 - Irrgang, Klaus-Dieter A1 - Renger, Gernot A1 - Lokstein, Heiko T1 - Stepwise two-photon excited fluorescence from higher excited states of chlorophylls in photosynthetic antenna complexes Y1 - 2006 UR - http://www.jbc.org/ U6 - https://doi.org/10.1074/jbc.M600080200 SN - 0021-9258 ER - TY - JOUR A1 - Lokstein, Heiko A1 - Hedke, Boris A1 - Mustroph, Angelika A1 - Kühn, Christina T1 - Signals, sensing, and plant primary metabolism Y1 - 2006 ER - TY - JOUR A1 - Oesterhelt, Christine A1 - Schmälzlin, Elmar A1 - Schmitt, Jürgen M. A1 - Lokstein, Heiko T1 - Regulation of photosynthesis in the unicellular acidophilic red alga Galdieria sulphuraria N2 - Extremophilic organisms are gaining increasing interest because of their unique metabolic capacities and great biotechnological potential. The unicellular acidophilic and mesothermophilic red alga Galdieria sulphuraria (074G) can grow autotrophically in light as well as heterotrophically in the dark. In this paper, the effects of externally added glucose on primary and secondary photosynthetic reactions are assessed to elucidate mixotrophic capacities of the alga. Photosynthetic O-2 evolution was quantified in an open system with a constant Supply Of CO2 to avoid rapid volatilization of dissolved inorganic carbon at low pH levels. In the presence of glucose, O-2 evolution was repressed even in illuminated cells. Ratios of variable to maximum chlorophyll fluorescence (F-v/F-m) and 77 Kfluorescence spectra indicated a reduced photochemical efficiency of photosystem II. The results were corroborated by strongly reduced levels of the photosystem 11 reaction centre protein D1. The downregulation of primary photosynthetic reactions was accompanied by reduced levels of the Calvin Cycle enzyme ribu lose-1,5-bisphosphate carboxylaselfoxygenase (Rubisco). Both effects depended on functional sugar uptake and are thus initiated by intracellular rather than extracellular glucose. Following glucose depletion, photosynthetic O-2 evolution of illuminated cells commenced after 15 h and Rubisco levels again reached the levels of autotrophic cells. It is concluded that true mixotrophy, involving electron transport across both photosystems, does not occur in G. sulphuraria 074G, and that heterotrophic growth is favoured over autotrophic growth if sufficient organic carbon is available. Y1 - 2007 UR - http://onlinelibrary.wiley.com/doi/10.1111/tpj.2007.51.issue-3/issuetoc U6 - https://doi.org/10.1111/j.1365-313X.2007.03159.x ER - TY - JOUR A1 - Krikunova, Maria A1 - Lokstein, Heiko A1 - Leupold, Dieter A1 - Hiller, Roger G. A1 - Voigt, B. T1 - Pigment-pigment interactions in PCP of Amphidinium carterae investigated by nonlinear polarization spectroscopy in the frequency domain N2 - Peridinin-chlorophyll a-protein (PCP) is a unique antenna complex in dinoflagellates that employs peridinin (a carotenoid) as its main light-harvesting pigment. Strong excitonic interactions between peridinins, as well as between peridinins and chlorophylls (Chls) a, can be expected from the short intermolecular distances revealed by the crystal structure. Different experimental approaches of nonlinear polarization spectroscopy in the frequency domain (NLPF) were used to investigate the various interactions between pigments in PCP of Amphidinium carterae at room temperature. Lineshapes of NLPF spectra indicate strong excitonic interactions between the peridinin's optically allowed S-2 (1Bu(+)) states. A comprehensive subband analysis of the distinct NLPF spectral substructure in the peridinin region allows us to assign peridinin subbands to the two Chls a in PCP having different S-1-state lifetimes. Peridinin subbands at 487, 501, and 535 nm were assigned to the longer-lived Chl, whereas a peridinin subband peaking at 515 nm was detected in both clusters. Certain peridinin(s), obviously corresponding to the subband centered at 487 nm, show(s) specific (possibly Coulombic?) interaction between the optically dark S-1(2A(g)(-)) and/or intramolecular charge- transfer (ICT) state and S-1 of Chl a. The NLPF spectrum, hence, indicates that this peridinin state is approximately isoenergetic or slightly above S-1 of Chl a. A global subband analysis of absorption and NLPF spectra reveals that the Chl a Q(y)-band consists of two subbands ( peaking at 669 and 675 nm and having different lifetimes), confirmed by NLPF spectra recorded at high pump intensities. At the highest applied pump intensities an additional band centered at <= 660 nm appears, suggesting-together with the above results-an assignment to a low-dipole moment S-0-> S-1/ICT transition of peridinin Y1 - 2006 ER - TY - JOUR A1 - Legall, Herbert A1 - Stiel, Holger A1 - Beck, Michael A1 - Leupold, Dieter A1 - Gruszecki, Wieslaw I. A1 - Lokstein, Heiko T1 - Near edge X-ray absorption fine structure spectroscopy (NEXAFS) of pigment-protein complexes : peridinin- chlorophyll a-protein (PCP) of Amphidinium carterae N2 - Peridinin-chlorophyll a protein (PCP) is a unique water soluble antenna complex that employs the carotenoid peridinin as the main light-harvesting pigment. In the present study the near edge X-ray absorption fine structure (NEXAFS) spectrum of PCP was recorded at the carbon Kedge. Additionally, the NEXAFS spectra of the constituent pigments, chlorophyll a and peridinin, were measured. The energies of the lowest unoccupied molecular levels of these pigments appearing in the carbon NEXAFS spectrum were resolved. Individual contributions of the pigments and the protein to the measured NEXAFS spectrum of PCP were determined using a "building block" approach combining NEXAFS spectra of the pigments and the amino acids constituting the PCP apoprotein. The results suggest that absorption changes of the pigments in the carbon near K-edge region can be resolved following excitation using a suitable visible pump laser pulse. Consequently, it may be possible to study excitation energy transfer processes involving "optically dark" states of carotenoids in pigment-protein complexes by soft X-ray probe optical pump double resonance spectroscopy (XODR). Y1 - 2007 UR - http://www.sciencedirect.com/science/journal/0165022X U6 - https://doi.org/10.1016/j.jbbm.2006.08.005 SN - 0165-022X ER - TY - JOUR A1 - Voigt, Bernd A1 - Krikunova, Maria A1 - Lokstein, Heiko T1 - Influence of detergent concentration on aggregation and the spectroscopic properties of light-harvesting complex II Y1 - 2008 U6 - https://doi.org/10.1007/s11120-007-9250-5 ER - TY - JOUR A1 - Shpilyov, Alexey V. A1 - Zinchenko, Vladislav V. A1 - Shestakov, Sergey V. A1 - Grimm, Bernhard A1 - Lokstein, Heiko T1 - Inactivation of the geranylgeranyl reductase (ChlP) gene in the cyanobacterium Synechocystis sp. PCC 6803 Y1 - 2005 ER - TY - JOUR A1 - Damaraju, Sridevi A1 - Schlede, Stephanie A1 - Eckhardt, Ulrich A1 - Lokstein, Heiko A1 - Grimm, Bernhard T1 - Functions of the water soluble chlorophyll-binding protein in plants JF - Journal of plant physiology : biochemistry, physiology, molecular biology and biotechnology of plants N2 - Functional aspects of water soluble chlorophyll-binding protein (WSCP) in plants were investigated during the courses of leaf senescence, chlorophyll biogenesis, stress response and photoprotection. The cDNA sequence encoding WSCP from cauliflower was cloned into a binary vector to facilitate Agrobacterium tumefaciens mediated transformation of Nicotiana tabacum. The resultant transgenic tobacco plants overexpressed the CauWSCP gene under the control of a 35S-promoter. Analyses of protein and pigment contents indicate that WSCP overexpression does not enhance chlorophyll catabolism in vivo, thus rendering a role of WSCP in Chl degradation unlikely. Accumulation of higher levels of protochlorophyllide in WSCP overexpressor plants corroborates a proposed temporary storage and carrier function of WSCP for chlorophyll and late precursors. Although WSCP overexpressor plants did not show significant differences in non-photochemical quenching of chlorophyll fluorescence, they are characterized by significantly lower zeaxanthin accumulation and peroxidase activity at different light intensities, even at high light intensities of 700-900 mu mol photons m(-2) s(-1). These results suggest a photoprotective function of the functional chlorophyll binding-WSCP tetramer by shielding of chlorophylls from molecular oxygen. KW - Chlorophyll metabolism KW - Non-photochemical quenching of chlorophyll fluorescence KW - Photooxidation KW - Photoprotection KW - Photosynthesis Y1 - 2011 U6 - https://doi.org/10.1016/j.jplph.2011.02.007 SN - 0176-1617 VL - 168 IS - 12 SP - 1444 EP - 1451 PB - Elsevier CY - Jena ER -