@article{LoksteinHoextermannLeupoldetal.2009, author = {Lokstein, Heiko and Hoextermann, Ekkehard and Leupold, Dieter and Garab, Gyoezoe and Renger, Gernot}, title = {A tribute : Professor Dr. Paul Hoffmann (March 28, 1931-July 10, 2008), a scientist with a great collaborative spirit}, issn = {0166-8595}, doi = {10.1007/s11120-009-9414-6}, year = {2009}, language = {en} } @article{MikhailyukKnoxPaschenkoetal.2006, author = {Mikhailyuk, Igor K. and Knox, Peter P. and Paschenko, Vladimir Z. and Razjivin, Andrej P. and Lokstein, Heiko}, title = {Analysis of absorption spectra of purple bacterial reaction centers in the near infrared region by higher order derivative spectroscopy}, doi = {10.1016/j.bpc.2006.02.002}, year = {2006}, abstract = {Reaction centers (RCs) of purple bacteria are uniquely suited objects to study the mechanisms of the photosynthetic conversion of light energy into chemical energy. A recently introduced method of higher order derivative spectroscopy [I.K. Mikhailyuk, H. Lokstein, A.P. Razjivin, A method of spectral subband decomposition by simultaneous fitting the initial spectrum and a set of its derivatives, J. Biochem. Biophys. Methods 63 (2005) 10-23] was used to analyze the NIR absorption spectra of RC preparations from Rhodobacter (R.) sphaeroides strain 2R and Blastochloris (B.) viridis strain KH, containing bacteriochlorophyll (BChl) a and b, respectively. Q(y) bands of individual RC porphyrin components (BChls and bacteriopheophytins, BPheo) were identified. The results indicate that the upper exciton level Py+ of the photo-active BChl dimer in RCs of R. sphaeroides has an absorption maximum of 810nm. The blue shift of a complex integral band at approximately 800nm upon oxidation of the RC is caused primarily by bleaching of Py+, rather than by an electrochromic shift of the absorption band(s) of the monomeric BChls. Likewise, the disappearance of a band peaking at 842 nm upon oxidation of RCs from B. viridis indicates that this band has to be assigned to Py+, A blue shift of an absorption band at approximately 830nm upon oxidation of RCs of B. viridis is also essentially caused by the disappearance of Py+, rather than by an electrochromic shift of the absorption bands of monomeric BChls. Absorption maxima of the monomeric BCHls, B-B and B-A are at 802 and 797nm, respectively, in RCs of R. sphaeroides at room temperature. BPheo co-factors H-B and HA peak at 748 and 758 nm, respectively, at room temperature. For B. viridis RCs the spectral positions of HB and HA were found to be 796 and 816nm, respectively, at room temperature.}, language = {en} } @article{KrikunovaLoksteinLeupoldetal.2006, author = {Krikunova, Maria and Lokstein, Heiko and Leupold, Dieter and Hiller, Roger G. and Voigt, B.}, title = {Pigment-pigment interactions in PCP of Amphidinium carterae investigated by nonlinear polarization spectroscopy in the frequency domain}, year = {2006}, abstract = {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}, language = {en} } @article{LoksteinHedkeMustrophetal.2006, author = {Lokstein, Heiko and Hedke, Boris and Mustroph, Angelika and K{\"u}hn, Christina}, title = {Signals, sensing, and plant primary metabolism}, year = {2006}, language = {en} } @article{LeupoldLoksteinScheer2006, author = {Leupold, Dieter and Lokstein, Heiko and Scheer, Hugo}, title = {Excitation energy transfer between (bacterio)chlorophylls : the role of excitonic coupling}, year = {2006}, language = {en} } @article{LegallStielBecketal.2007, author = {Legall, Herbert and Stiel, Holger and Beck, Michael and Leupold, Dieter and Gruszecki, Wieslaw I. and Lokstein, Heiko}, title = {Near edge X-ray absorption fine structure spectroscopy (NEXAFS) of pigment-protein complexes : peridinin- chlorophyll a-protein (PCP) of Amphidinium carterae}, issn = {0165-022X}, doi = {10.1016/j.jbbm.2006.08.005}, year = {2007}, abstract = {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).}, language = {en} } @article{OesterheltSchmaelzlinSchmittetal.2007, author = {Oesterhelt, Christine and Schm{\"a}lzlin, Elmar and Schmitt, J{\"u}rgen M. and Lokstein, Heiko}, title = {Regulation of photosynthesis in the unicellular acidophilic red alga Galdieria sulphuraria}, doi = {10.1111/j.1365-313X.2007.03159.x}, year = {2007}, abstract = {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.}, language = {en} } @article{ShpilyovZinchenkoShestakovetal.2005, author = {Shpilyov, Alexey V. and Zinchenko, Vladislav V. and Shestakov, Sergey V. and Grimm, Bernhard and Lokstein, Heiko}, title = {Inactivation of the geranylgeranyl reductase (ChlP) gene in the cyanobacterium Synechocystis sp. PCC 6803}, year = {2005}, language = {en} } @article{GruszeckiStielNiedzwiedzkietal.2005, author = {Gruszecki, Wieslaw I. and Stiel, H. and Niedzwiedzki, Dariusz and Beck, Michael and Milanowska, J. and Lokstein, Heiko and Leupold, Dieter}, title = {Towards elucidating the energy of the first excited singlet state of xanthophyll cycle pigments investigated by x-ray absorption spectroscopy}, year = {2005}, language = {en} } @article{MikhailyukLoksteinRazjivin2005, author = {Mikhailyuk, Igor K. and Lokstein, Heiko and Razjivin, Andrei P.}, title = {A method of spectral subband decomposition by simultaneous fitting the initial spectrum and a set of its derivatives}, year = {2005}, abstract = {An improved method for spectral subband decomposition based on simultaneous fitting of the initial spectrum and a set of its derivatives is introduced. Additionally, it procedure for finding an optimal smoothing filter to obtain undistorted derivatives IS Suggested. The proposed method is demonstrated with a model spectrum as well its with experimental absorption spectra of the photosynthetic antenna complexes, peridinin-chlorophyll a-protein (PCP) and the main light-harvesting complex of higher plants (LHC II). (c) 2005 Elsevier B.V. All rights reserved}, language = {en} } @article{BetkeLokstein2019, author = {Betke, Alexander and Lokstein, Heiko}, title = {Two-photon excitation spectroscopy of photosynthetic light-harvesting complexes and pigments}, series = {Faraday discussions}, volume = {216}, journal = {Faraday discussions}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1359-6640}, doi = {10.1039/c8fd00198g}, pages = {494 -- 506}, year = {2019}, abstract = {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.}, language = {en} } @article{LandauLoksteinSchelleretal.2009, author = {Landau, Alejandra Mabel and Lokstein, Heiko and Scheller, Henrik Vibe and Lainez, Veronica and Maldonado, Sara and Prina, Alberto Ra{\´u}l}, title = {A cytoplasmically inherited barley mutant is defective in photosystem I assembly due to a temperature-sensitive defect in ycf3 splicing}, issn = {0032-0889}, doi = {10.1104/pp.109.147843}, year = {2009}, abstract = {A cytoplasmically inherited chlorophyll-deficient mutant of barley (Hordeum vulgare) termed cytoplasmic line 3 (CL3), displaying a viridis (homogeneously light-green colored) phenotype, has been previously shown to be affected by elevated temperatures. In this article, biochemical, biophysical, and molecular approaches were used to study the CL3 mutant under different temperature and light conditions. The results lead to the conclusion that an impaired assembly of photosystem I (PSI) under higher temperatures and certain light conditions is the primary cause of the CL3 phenotype. Compromised splicing of ycf3 transcripts, particularly at elevated temperature, resulting from a mutation in a noncoding region (intron 1) in the mutant ycf3 gene results in a defective synthesis of Ycf3, which is a chaperone involved in PSI assembly. The defective PSI assembly causes severe photoinhibition and degradation of PSII.}, language = {en} } @article{FritzLoksteinHackenbergetal.2007, author = {Fritz, Markus and Lokstein, Heiko and Hackenberg, Dieter and Welti, Ruth and Roth, Mary and Z{\"a}hringer, Ulrich and Fulda, Martin and Hellmeyer, Wiebke and Ott, Claudia and Wolter, Frank P. and Heinz, Ernst}, title = {Channeling of eukaryotic diacylglycerol into the biosynthesis of plastidial phosphatidylglycerol}, issn = {0021-9258}, doi = {10.1074/jbc.M606295200}, year = {2007}, abstract = {Plastidial glycolipids contain diacylglycerol (DAG) moieties, which are either synthesized in the plastids (prokaryotic lipids) or originate in the extraplastidial compartment (eukaryotic lipids) necessitating their transfer into plastids. In contrast, the only phospholipid in plastids, phosphatidylglycerol (PG), contains exclusively prokaryotic DAG backbones. PG contributes in several ways to the functions of chloroplasts, but it is not known to what extent its prokaryotic nature is required to fulfill these tasks. As a first step toward answering this question, we produced transgenic tobacco plants that contain eukaryotic PG in thylakoids. This was achieved by targeting a bacterial DAG kinase into chloroplasts in which the heterologous enzyme was also incorporated into the envelope fraction. From lipid analysis we conclude that the DAG kinase phosphorylated eukaryotic DAG forming phosphatidic acid, which was converted into PG. This resulted in PG with 2-3 times more eukaryotic than prokaryotic DAG backbones. In the newly formed PG the unique Delta 3-trans-double bond, normally confined to 3-transhexadecenoic acid, was also found in sn-2- bound cis-unsaturated C18 fatty acids. In addition, a lipidomics technique allowed the characterization of phosphatidic acid, which is assumed to be derived from eukaryotic DAG precursors in the chloroplasts of the transgenic plants. The differences in lipid composition had only minor effects on measured functions of the photosynthetic apparatus, whereas the most obvious phenotype was a significant reduction in growth.}, language = {en} } @article{VoigtKrikunovaLokstein2008, author = {Voigt, Bernd and Krikunova, Maria and Lokstein, Heiko}, title = {Influence of detergent concentration on aggregation and the spectroscopic properties of light-harvesting complex II}, doi = {10.1007/s11120-007-9250-5}, year = {2008}, language = {en} } @article{NordhuesSchoettlerUngeretal.2012, author = {Nordhues, Andre and Sch{\"o}ttler, Mark Aurel and Unger, Ann-Katrin and Geimer, Stefan and Sch{\"o}nfelder, Stephanie and Schmollinger, Stefan and Ruetgers, Mark and Finazzi, Giovanni and Soppa, Barbara and Sommer, Frederik and M{\"u}hlhaus, Timo and Roach, Thomas and Krieger-Liszkay, Anja and Lokstein, Heiko and Luis Crespo, Jose and Schroda, Michael}, title = {Evidence for a role of VIPP1 in the structural organization of the photosynthetic apparatus in chlamydomonas}, series = {The plant cell}, volume = {24}, journal = {The plant cell}, number = {2}, publisher = {American Society of Plant Physiologists}, address = {Rockville}, issn = {1040-4651}, doi = {10.1105/tpc.111.092692}, pages = {637 -- 659}, year = {2012}, abstract = {The vesicle-inducing protein in plastids (VIPP1) was suggested to play a role in thylakoid membrane formation via membrane vesicles. As this functional assignment is under debate, we investigated the function of VIPP1 in Chlamydomonas reinhardtii. Using immunofluorescence, we localized VIPP1 to distinct spots within the chloroplast. In VIPP1-RNA interference/artificial microRNA cells, we consistently observed aberrant, prolamellar body-like structures at the origin of multiple thylakoid membrane layers, which appear to coincide with the immunofluorescent VIPP1 spots and suggest a defect in thylakoid membrane biogenesis. Accordingly, using quantitative shotgun proteomics, we found that unstressed vipp1 mutant cells accumulate 14 to 20\% less photosystems, cytochrome b(6)f complex, and ATP synthase but 30\% more light-harvesting complex II than control cells, while complex assembly, thylakoid membrane ultrastructure, and bulk lipid composition appeared unaltered. Photosystems in vipp1 mutants are sensitive to high light, which coincides with a lowered midpoint potential of the Q(A)/Q(A)(-) redox couple and increased thermosensitivity of photosystem II (PSII), suggesting structural defects in PSII. Moreover, swollen thylakoids, despite reduced membrane energization, in vipp1 mutants grown on ammonium suggest defects in the supermolecular organization of thylakoid membrane complexes. Overall, our data suggest a role of VIPP1 in the biogenesis/assembly of thylakoid membrane core complexes, most likely by supplying structural lipids.}, language = {en} } @misc{LoksteinBetkeKrikunovaetal.2012, author = {Lokstein, Heiko and Betke, Alexander and Krikunova, Maria and Teuchner, Klaus and Voigt, Bernd}, title = {Elucidation of structure-function relationships in plant major light-harvesting complex (LHC II) by nonlinear spectroscopy}, series = {Photosynthesis research}, volume = {111}, journal = {Photosynthesis research}, number = {1-2}, publisher = {Springer}, address = {Dordrecht}, issn = {0166-8595}, doi = {10.1007/s11120-011-9700-y}, pages = {227 -- 235}, year = {2012}, abstract = {Conventional linear and time-resolved spectroscopic techniques are often not appropriate to elucidate specific pigment-pigment interactions in light-harvesting pigment-protein complexes (LHCs). Nonlinear (laser-) spectroscopic techniques, including nonlinear polarization spectroscopy in the frequency domain (NLPF) as well as step-wise (resonant) and simultaneous (non-resonant) two-photon excitation spectroscopies may be advantageous in this regard. Nonlinear spectroscopies have been used to elucidate substructure(s) of very complex spectra, including analyses of strong excitonic couplings between chlorophylls and of interactions between (bacterio) chlorophylls and "optically dark'' states of carotenoids in LHCs, including the major antenna complex of higher plants, LHC II. This article shortly reviews our previous study and outlines perspectives regarding the application of selected nonlinear laser-spectroscopic techniques to disentangle structure-function relationships in LHCs and other pigment-protein complexes.}, language = {en} } @article{DamarajuSchledeEckhardtetal.2011, author = {Damaraju, Sridevi and Schlede, Stephanie and Eckhardt, Ulrich and Lokstein, Heiko and Grimm, Bernhard}, title = {Functions of the water soluble chlorophyll-binding protein in plants}, series = {Journal of plant physiology : biochemistry, physiology, molecular biology and biotechnology of plants}, volume = {168}, journal = {Journal of plant physiology : biochemistry, physiology, molecular biology and biotechnology of plants}, number = {12}, publisher = {Elsevier}, address = {Jena}, issn = {0176-1617}, doi = {10.1016/j.jplph.2011.02.007}, pages = {1444 -- 1451}, year = {2011}, abstract = {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.}, language = {en} } @article{EbenhoehHouwaartLoksteinetal.2011, author = {Ebenhoeh, Oliver and Houwaart, Torsten and Lokstein, Heiko and Schlede, Stephanie and Tirok, Katrin}, title = {A minimal mathematical model of nonphotochemical quenching of chlorophyll fluorescence}, series = {Biosystems : journal of biological and information processing sciences}, volume = {103}, journal = {Biosystems : journal of biological and information processing sciences}, number = {2}, publisher = {Elsevier}, address = {Oxford}, issn = {0303-2647}, doi = {10.1016/j.biosystems.2010.10.011}, pages = {196 -- 204}, year = {2011}, abstract = {Under natural conditions, plants are exposed to rapidly changing light intensities. To acclimate to such fluctuations, plants have evolved adaptive mechanisms that optimally exploit available light energy and simultaneously minimise damage of the photosynthetic apparatus through excess light. An important mechanism is the dissipation of excess excitation energy as heat which can be measured as nonphotochemical quenching of chlorophyll fluorescence (NPQ). In this paper, we present a highly simplified mathematical model that captures essential experimentally observed features of the short term adaptive quenching dynamics. We investigate the stationary and dynamic behaviour of the model and systematically analyse the dependence of characteristic system properties on key parameters such as rate constants and pool sizes. Comparing simulations with experimental data allows to derive conclusions about the validity of the simplifying assumptions and we further propose hypotheses regarding the role of the xanthophyll cycle in NPQ. We envisage that the presented theoretical description of the light reactions in conjunction with short term adaptive processes serves as a basis for the development of more detailed mechanistic models by which the molecular mechanisms of NPQ can be theoretically studied.}, language = {en} }