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279 results on '"Lokstein, Heiko"'

3. Photo-protection/photo-damage in natural systems: general discussion

Author

Ashfold, Michael, Bai, Shuming, Bradforth, Stephen, Chabera, Pavel, Cina, Jeffrey, Crespo-Hernández, Carlos E, das Neves Rodrigues, Natércia, Duchi, Marta, Fleming, Graham, Grieco, Christopher, Habershon, Scott, Haggmark, Michael, Hammes-Schiffer, Sharon, Hsieh, Shou-Ting, Kohler, Bern, Lokstein, Heiko, Marcus, Andrew, Martinez, Todd, Matsika, Spiridoula, Oliver, Thomas AA, Ortiz-Rodríguez, Luis, Polivka, Tomas, Son, Minjung, Stavros, Vasilios, Steen, Collin, Turner, Matthew, Walla, Peter Jomo, and Woolley, Jack

Subjects
Energy Transfer, Microalgae, Photochemical Processes, Chemical Sciences, Chemical Physics
Published
2019

5. Insights into the binding behavior of native and non-native cytochromes to photosystem I from Thermosynechococcus elongatus

Author

Kölsch, Adrian, Hejazi, Mahdi, Stieger, Kai R, Feifel, Sven C, Kern, Jan F, Müh, Frank, Lisdat, Fred, Lokstein, Heiko, and Zouni, Athina

Subjects
Chemical Sciences, Physical Chemistry, Animals, Bacterial Proteins, Binding Sites, Cyanobacteria, Cytochromes c, Cytochromes c6, Horses, Molecular Docking Simulation, Osmolar Concentration, Photosystem I Protein Complex, Static Electricity, complex, crystallography, cytochrome c, docking, photosynthesis, photosystem I, Biological Sciences, Medical and Health Sciences, Biochemistry & Molecular Biology, Biological sciences, Biomedical and clinical sciences, Chemical sciences
Abstract

The binding of photosystem I (PS I) from Thermosynechococcus elongatus to the native cytochrome (cyt) c6 and cyt c from horse heart (cyt cHH) was analyzed by oxygen consumption measurements, isothermal titration calorimetry (ITC), and rigid body docking combined with electrostatic computations of binding energies. Although PS I has a higher affinity for cyt cHH than for cyt c6, the influence of ionic strength and pH on binding is different in the two cases. ITC and theoretical computations revealed the existence of unspecific binding sites for cyt cHH besides one specific binding site close to P700 Binding to PS I was found to be the same for reduced and oxidized cyt cHH Based on this information, suitable conditions for cocrystallization of cyt cHH with PS I were found, resulting in crystals with a PS I:cyt cHH ratio of 1:1. A crystal structure at 3.4-Å resolution was obtained, but cyt cHH cannot be identified in the electron density map because of unspecific binding sites and/or high flexibility at the specific binding site. Modeling the binding of cyt c6 to PS I revealed a specific binding site where the distance and orientation of cyt c6 relative to P700 are comparable with cyt c2 from purple bacteria relative to P870 This work provides new insights into the binding modes of different cytochromes to PS I, thus facilitating steps toward solving the PS I-cyt c costructure and a more detailed understanding of natural electron transport processes.

Published
2018

26. Photosynthetic Light-Harvesting (Antenna) Complexes - Structures and Functions

Author

Lokstein, Heiko, Renger, Gernot, and Götze, Jan P.

Subjects
chlorophylls, light-harvesting complexes, photosynthesis, pigment-protein complexes, carotenoids, excitation energy transfer, 500 Naturwissenschaften und Mathematik::540 Chemie::541 Physikalische Chemie, photosystems, bacteriochlorophylls, 500 Naturwissenschaften und Mathematik::540 Chemie::540 Chemie und zugeordnete Wissenschaften
Abstract

Chlorophylls and bacteriochlorophylls, together with carotenoids, serve, noncovalently bound to specific apoproteins, as principal light-harvesting and energy-transforming pigments in photosynthetic organisms. In recent years, enormous progress has been achieved in the elucidation of structures and functions of light-harvesting (antenna) complexes, photosynthetic reaction centers and even entire photosystems. It is becoming increasingly clear that light-harvesting complexes not only serve to enlarge the absorption cross sections of the respective reaction centers but are vitally important in short- and long-term adaptation of the photosynthetic apparatus and regulation of the energy-transforming processes in response to external and internal conditions. Thus, the wide variety of structural diversity in photosynthetic antenna “designs” becomes conceivable. It is, however, common for LHCs to form trimeric (or multiples thereof) structures. We propose a simple, tentative explanation of the trimer issue, based on the 2D world created by photosynthetic membrane systems.

Published
2021
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35. Spectral substructure and excitonic interactions in the minor photosystem II antenna complex CP29 as revealed by nonlinear polarization spectroscopy in the freuency domain

Author

Voigt, Bernd, Irrgang, Klaus-Dieter, Ehlert, Jurgen, Beenken, Wichard, Renger, Gernot, Leupold, Dieter, and Lokstein, Heiko

Subjects
Photosynthesis research -- Analysis, Chloroplast pigments -- Physiological aspects, Absorption spectra -- Evaluation, Structure-activity relationships (Biochemistry) -- Analysis, Biological sciences, Chemistry
Abstract

Results reveal pronounced excitonic interactions between chlorophyll a and b molecules, suggesting that the spectral heterogeneity of a minor photosystem II antenna complex includes contribution of the chlorophyll molecules as well as the contribution from the pigment-protein interactions.

Published
2002

36. Assignment of spectral substructures to pigment-binding sites in higher plant light-harvesting complex LHC-II

Author

Rogi, Hans, Schodel, Rene, Lokstein, Heiko, Kuhlbrandt, Werner, and Schubert, Axel

Subjects
Photosynthesis research -- Analysis, Chlorophyll -- Analysis, Binding sites (Biochemistry) -- Analysis, Spectrum analysis -- Research, Biological sciences, Chemistry
Abstract

Research examines the spectral heterogeneity of chlorophylls in the light harvesting complex II of photosynthetic apparatus. Low temperature absorption spectroscopy of a recombinant LHC-II complex reveals that chlorophylls at specific binding sites can be correlated with distinct spectral sub-bands, representing absorption spectra of native and refolded LHC-II complex.

Published
2002

43. Spectrally selective fluorescence imaging of Chlorobaculum tepidum reaction centers conjugated to chelator-modified silver nanowires

Author

Kowalska, Dorota, Szalkowski, Marcin, Ashraf, Khuram, Grzelak, Justyna, Lokstein, Heiko, Niedziolka-Jonsson, Joanna, Cogdell, Richard, and Mackowski, Sebastian

Subjects
macromolecular substances
Abstract

A polyhistidine tag (His-tag) present on Chlorobaculum tepidum reaction centers (RCs) was used to immobilize photosynthetic complexes on a silver nanowire (AgNW) modified with nickel-chelating nitrilo-triacetic acid (Ni-NTA). The optical properties of conjugated nanostructures were studied using wide-field and confocal fluorescence microscopy. Plasmonic enhancement of RCs conjugated to AgNWs was observed as their fluorescence intensity dependence on the excitation wavelength does not follow the excitation spectrum of RC complexes in solution. The strongest effect of plasmonic interactions on the emission intensity of RCs coincides with the absorption spectrum of AgNWs and is observed for excitation into the carotenoid absorption. From the absence of fluorescence decay shortening, we attribute the emission enhancement to increase of absorption in RC complexes.

Published
2018

48. On the Electronic Structure of Cu Chlorophyllin and Its Breakdown Products : A Carbon K-Edge X-ray Absorption Spectroscopy Study

Author

Witte, Katharine, Mantouvalou, Ioanna, Sanchez-de-Armas, Rocio, Lokstein, Heiko, Lebendig-Kuhla, Janina, Jonas, Adrian, Roth, Friedrich, Kanngiesser, Birgit, Stiel, Holger, Witte, Katharine, Mantouvalou, Ioanna, Sanchez-de-Armas, Rocio, Lokstein, Heiko, Lebendig-Kuhla, Janina, Jonas, Adrian, Roth, Friedrich, Kanngiesser, Birgit, and Stiel, Holger

Abstract

Using near-edge X-ray absorption fine structure (NEXAFS) spectroscopy, the carbon backbone of sodium copper chlorophyllin (SCC), a widely used chlorophyll derivative, and its breakdown products are analyzed to elucidate their electronic structure and physicochemical properties. Using various sample preparation methods and complementary spectroscopic methods (including UV/Vis, X-ray photoelectron spectroscopy), a comprehensive insight into the SCC breakdown process is presented. The experimental results are supported by density functional theory calculations, allowing a detailed assignment of characteristic NEXAFS features to specific C bonds. SCC can be seen as a model system for the large group of porphyrins; thus, this work provides a novel and detailed description of the electronic structure of the carbon backbone of those molecules and their breakdown products. The achieved results also promise prospective optical pump/X-ray probe investigations of dynamic processes in chlorophyll-containing photosynthetic complexes to be analyzed more precisely.

Published
2018
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49. On the Electronic Structure of Cu Chlorophyllin and Its Breakdown Products: A Carbon K-Edge X-ray Absorption Spectroscopy Study

Author

Universidad de Sevilla. Departamento de Química Física, German Minister für Bildung und Forschung (BMBF), European Union (UE), Czech Science Foundation. GACR, Witte, Katharina, Mantouvalou, Ioanna, Sánchez de Armas, María Rocío, Lokstein, Heiko, Lebendig-Kuhla, Janina, Jonas, Adrian, Roth, Friedrich, Kanngießer, Birgit, Stiel, Holger, Universidad de Sevilla. Departamento de Química Física, German Minister für Bildung und Forschung (BMBF), European Union (UE), Czech Science Foundation. GACR, Witte, Katharina, Mantouvalou, Ioanna, Sánchez de Armas, María Rocío, Lokstein, Heiko, Lebendig-Kuhla, Janina, Jonas, Adrian, Roth, Friedrich, Kanngießer, Birgit, and Stiel, Holger

Abstract

Using near-edge X-ray absorption fine structure (NEXAFS) spectroscopy, the carbon backbone of sodium copper chlorophyllin (SCC), a widely used chlorophyll derivative, and its breakdown products are analyzed to elucidate their electronic structure and physicochemical properties. Using various sample preparation methods and complementary spectroscopic methods (including UV/Vis, X-ray photoelectron spectroscopy), a comprehensive insight into the SCC breakdown process is presented. The experimental results are supported by density functional theory calculations, allowing a detailed assignment of characteristic NEXAFS features to specific C bonds. SCC can be seen as a model system for the large group of porphyrins; thus, this work provides a novel and detailed description of the electronic structure of the carbon backbone of those molecules and their breakdown products. The achieved results also promise prospective optical pump/X-ray probe investigations of dynamic processes in chlorophyll-containing photosynthetic complexes to be analyzed more precisely.

Published
2018

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