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  • Articles  (11)
  • Articles: DFG German National Licenses  (11)
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  • Life and Medical Sciences
  • Nuclear reaction
  • Photosynthesis
  • Springer  (11)
  • Physics  (11)
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  • Articles  (11)
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  • Articles: DFG German National Licenses  (11)
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  • 1
    Electronic Resource
    Electronic Resource
    A model for the evolution of photosynthetic oxygen (1978)
    Springer
    Pure and applied geophysics 116 (1978), S. 234-238 
    Details
    ISSN: 1420-9136
    Keywords: Atmospheric evolution ; 13C ; Photosynthesis ; Sedimentary mass
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01636881
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  • 2
    Electronic Resource
    Electronic Resource
    The early history of oxygen and ozone in the atmosphere (1978)
    Springer
    Pure and applied geophysics 117 (1978), S. 498-512 
    Details
    ISSN: 1420-9136
    Keywords: History of atmosphere ; Oxygen ; Ozone ; Photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract There may have been three stages in the growth of oxygen in the terrestrial atmosphere. Prior to the origin of photosynthesis the only source of oxygen was photolysis of water vapor followed by escape of hydrogen to space. The rate of this process was probably less than the rate of release of reduced gases (principally hydrogen) from volcanoes, so the oxygen partial pressure was held to negligibly low values by photochemical reactions with an excess of hydrogen. The photosynthetic source of oxygen was probably in operation as long ago as 3.8 billion years. It released oxygen to the ocean. Presumably most of this oxygen was destroyed in the ocean as long as its rate of supply was less than the rate of supply of readily oxidizable material (principally Fe2+) provided by the weathering of rocks. This phase appears to have lasted until about 2 billion years ago, during which period most banded iron formations were deposited. During this period the production of oxygen by algae was limited by competition with photosynthetic bacteria, which preempted the supply of nutrient phosphorus as long as reduced chemicals were available in the environment. Once the photosynthetic oxygen source exceeded the rate of supply of reduced minerals exposed by erosion and weathering, the accumulation of oxygen in the ocean and atmosphere could be controlled only by reaction of oxygen with reduced organic material. This is the stabilization mechanism that operates today. It seems unlikely that oxygen could be consumed at a significant rate by this process until oxygen levels sufficiently high to support respiration had been achieved. I therefore suggest that atmospheric oxygen rose rapidly from essentially zero to approximately its present value (within a factor of 10) when the photosynthetic source of oxygen rose above the weathering source of reduced minerals, probably about 2 billion years ago. The ozone layer and the ultraviolet screen were absent prior to this time and essentially fully developed after this time.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00876630
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  • 3
    Electronic Resource
    Electronic Resource
    The biota as ancient and modern modulator of the Earth's atmosphere (1978)
    Springer
    Pure and applied geophysics 116 (1978), S. 239-243 
    Details
    ISSN: 1420-9136
    Keywords: Gaia ; Paleoatmospheres ; Atmospheric oxygen ; Photosynthesis ; Microbial gas exchange
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The composition of the Earth's atmosphere is thought to have been highly modified by surface microbiotas and modulated around quantities of gases optimized for growth of these microbiotas. Three diagrams are presented: The first shows a probable order of appearance of major metabolic pathways in microbes that interact with sediment and atmosphere. It is based on evolutionary considerations and was devised independently of the fossil record. The second diagram shows the qualitative emissions and removals of atmospheric gases by obligately anaerobic organisms; it approximates those processes thought to have dominated the Earth's atmosphere in Archean times. The third diagrams gaseous emissions and removals by the major groups of organisms, including oxygen-releasing and utilizing forms. Biological gas exchange processes thought to have dominated the atmosphere since the Proterozoic are thus represented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01636882
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  • 4
    Electronic Resource
    Electronic Resource
    Long-term global sea surface temperature fluctuations and their possible influence on atmospheric CO2 concentrations (1978)
    Springer
    Pure and applied geophysics 116 (1978), S. 351-371 
    Details
    ISSN: 1420-9136
    Keywords: CO2 variation ; Nutrients ; Photosynthesis ; Sea surface temperature ; Upwelling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Changes of atmospheric CO2 concentration since 1958 are shown to be related to sea surface temperature changes. The largest contribution to changes arises from the Pacific equatorial upwelling region, with the Indian Ocean and Atlantic contributing only small fractions to the variance. It is hypothesized that the observed relationship is related to the nutrients that are brought up by upwelling cold water, with photosynthesis contributing to a lowering of the partial pressure of CO2 in the sea and thus to a greater tendency for a flux from the air to the sea. Possible longer term variations of sea temperature and CO2 are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01636891
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  • 5
    Electronic Resource
    Electronic Resource
    Oxygen and hydrogen in the primitive atmosphere (1978)
    Springer
    Pure and applied geophysics 116 (1978), S. 222-231 
    Details
    ISSN: 1420-9136
    Keywords: Photolysis ; Photosynthesis ; Primitive Atmosphere
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract From time to time there appears in the literature the assertion that photolysis of water vapor could have maintained an appreciable concentration of oxygen in the primitive (prebiological) atmosphere. The implausibility of this assertion is argued in this paper. By itself, photolysis does not provide a source of oxygen because it is usually followed by recombination of the products of photolysis. Only the escape to space (at a much smaller rate) of the hydrogen produced by photolysis of water results in a net source of oxygen. The oxidation state of the primitive atmosphere depended on the relative magnitudes of this net source of oxygen and a volcanic source of hydrogen and other reduced gases. Today the volcanic source of reduced gases is approximately equal to the oxygen source provided by photolysis followed by escape. The oxygen source depends on the mixing ratio of water vapor in the stratosphere, which ultimately determines the rate of escape of hydrogen produced from water vapor. Its magnitude may not have been very different in the past. The volcanic source of hydrogen, on the other hand, is likely to have been much larger when the earth was tectonically young. Hydrogen was therefore released to the primitive atmosphere more rapidly than oxygen, probably. Photochemical reactions with the excess hydrogen maintained oxygen mixing ratios at negligibly small levels. The hydrogen mixing ratio was determined by a balance between the volcanic source (reduced by recombination with oxygen) and escape to space. In time, either because of decline of the volcanic source of hydrogen or because of addition of a biological source of oxygen, the input of oxygen to the atmosphere rose above the input of hydrogen. The oxidation state of the atmosphere changed rapidly. Volcanic hydrogen was now consumed by photochemical reactions with excess oxygen, while the oxygen mixing ratio was determined by a balance between the source (reduced by recombination with volcanic hydrogen) and consumption in reactions with reduced material at the surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01636879
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  • 6
    Electronic Resource
    Electronic Resource
    Increase in the CO2 exchange rate of leaves of Ilex rotunda with elevated atmospheric CO2 concentration in an urban canyon (1998)
    Springer
    International journal of biometeorology 42 (1998), S. 16-21 
    Details
    ISSN: 1432-1254
    Keywords: Key words Carbon dioxide ; Photosynthesis ; Street tree ; Simulation model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Abstract  It was found that the atmospheric carbon dioxide (CO2) concentration in an urban canyon in Fukuoka city, Japan during August 1997 was about 30 µmol mol−1 higher than that in the suburbs. When fully exposed to sunlight, in situ the rate of photosynthesis in single leaves of Ilex rotunda planted in the urban canyon was higher when the atmospheric CO2 concentration was elevated. A biochemically based model was able to predict the in situ rate of photosynthesis well. The model also predicted an increase in the daily CO2 exchange rate for leaves in the urban canyon with an increase in atmospheric CO2 concentration. However, in situ such an increase in the daily CO2 exchange rate may be offset by diminished sunlight, a higher air temperature and a lower relative humidity. Thus, the daily CO2 exchange rate predicted using the model based soleley on the environmental conditions prevailing in the urban canyon was lower than that predicted based only on environmental factors found in the suburbs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004840050078
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  • 7
    Electronic Resource
    Electronic Resource
    ESR and ENDOR of primary reactants in photosynthesis (1982)
    Springer
    European biophysics journal 8 (1982), S. 107-150 
    Details
    ISSN: 1432-1017
    Keywords: Photosynthesis ; Primary reactions ; ESR ; ENDOR ; Chlorophyll ; Bacteriochlorophyll ; Pheophytin ; Bacteriopheophytin ; Ferredoxin ; Iron-sulfur protein
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The primary reactants in photosynthesis are defined as the chemical entities on which charges are generated and stabilized after capture of a photon by the photochemical trap: PIX → hv P * IX → P + I − X→ P + IX −, where P stands for the primary electron donor, P * for its excited singlet state, I for the ‘first’ (ESR-detectable) electron acceptor and X for the secondary acceptor complex. The ESR and ENDOR experiments which have played a rÔle in the identification and characterization of P, I, and X in the bacterial and plant photosystems are comprehensively reviewed. The structural and kinetic information obtained with magnetic resonance techniques are integrated with results obtained with optical spectroscopy to give a unified picture of the pathway of primary photochemistry in photosynthesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00535455
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  • 8
    Electronic Resource
    Electronic Resource
    Pigment-protein interactions in Rhodobacter sphaeroides Y photochemical reaction center; comparison with other reaction center structures (1996)
    Springer
    European biophysics journal 24 (1996), S. 233-242 
    Details
    ISSN: 1432-1017
    Keywords: Bacterial reaction center ; Crystal structure ; Cofactor interactions ; Structure comparison ; Photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Structural characteristics of pigments and cofactors are analyzed in the X-ray structure of the Rhodobacter sphaeroides (Y strain) photochemical reaction center, recently refined at 3 Å resolution (Arnoux B, Gaucher JF, Ducruix A and Reiss-Husson F (1995) Acta Cryst D51: 368–379). As several structures are now available for these pigment-protein complexes from various Rhodobacter sphaeroides strains and for Rhodopseudomonas viridis, a detailed comparison was done for highlighting converging structural results as well as for pointing to incidental differences. Comparison of mean plane orientations and distances, and also direct superposition of the pigment arrays, indicated that the best agreement between all the structures concerned the dimer and the bacteriopheophytin of the A branch. In the Y reaction center structure the pentacoordination of the Mg++ atoms of the bacteriochlorophylls, and the H bonding pattern of the porphyrin conjugated carbonyls are consistent with the better resolved Rhodobacter sphaeroides recently published structure (Ermler U, Fritzsch G, Buchanan SK and Michel H (1995) Structure 2:925–936). Discrepancies between the various Rhodobacter sphaeroides structures are larger for the quinones, particularly the secondary one. In the Y reaction center structure the phytyl and isoprenoid chains of the cofactors are defined and their local mobility was evaluated by analyzing the temperature factor and the density of neighbouring atoms. Significant differences were observed between the A and B branches, and, within each branch, from the dimer to the quinone molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00205104
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  • 9
    Electronic Resource
    Electronic Resource
    Gramicidin in chromatophores of Rhodobacter sphaeroides (1991)
    Springer
    European biophysics journal 19 (1991), S. 213-216 
    Details
    ISSN: 1432-1017
    Keywords: Photosynthesis ; Chromatophore ; Gramicidin ; Electrochromism ; Size analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Chromatophores of Rhodobacter sphaeroides were excited with light flashes to generate a transmembrane electrical potential difference. The electric relaxation was measured by electrochromic absorption changes as a function of added gramicidin. At low gramicidin/bacteriochlorophyll (BChl) molar ratios the decay of the electrochromic absorption changes showed a biphasic behaviour, with a fast phase relaxing at some μs, and a slow phase relaxing at more than 100 ms. This was attributable to a mixture of vesicles containing gramicidin dimers with others containing none. The concentration dependence of this effect was linear. This implied full dimerization of gramicidin. The data were interpreted to yield an average bacteriochlorophyll content per chromatophore of 770(±150) and the conductance of a single gramicidin dimer in the chromatophore membrane of 15(±4) pS (in about 115 mM KCl).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00196347
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  • 10
    Electronic Resource
    Electronic Resource
    Electron Paramagnetic Resonance investigation of the interaction of nitroxyl spin labels with photosynthetic membranes (1996)
    Springer
    Journal of biological physics 22 (1996), S. 175-185 
    Details
    ISSN: 1573-0689
    Keywords: Photosynthesis ; Photosynthetic membranes ; Chloroplasts ; Liposomes ; Spin labels ; EPR spectra ; pH optimum ; Photosynthetic electron transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The interactions of four nytroxyl spin labels with photosynthetic membranes (thylakoids and liposomes) have been investigated by the Electron Paramagnetic Resonance technique (EPR). The obtained data (shapes of EPR spectra and kinetics of light induced reactions) allow us to localize the interactions between the markers and photosynthetic membranes. The pH influence on the reaction kinetics has also been investigated. On the basis of these experimental data, a theoretical model of the interaction between spin labels and the photosynthetic electron transport chain is proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00417649
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