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  • Photosystem II  (1)
  • Photosystem II core complex  (1)
  • Substitutional Bias  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Substitutional bias confounds inference of cyanelle origins from sequence data (1992)
    Springer
    Journal of molecular evolution 34 (1992), S. 153-162 
    Details
    ISSN: 1432-1432
    Keywords: Phylogenetic inference ; Stationarity ; Substitutional Bias ; Compositional bias ; Cyanelle ; Cyanophora paradoxa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Available molecular and biochemical data offer conflicting evidence for the origin of the cyanelle of Cyanophora paradoxa. We show that the similarity of cyanelle and green chloroplast sequences is probably a result of these two lineages independently developing the same pattern of directional nucleotide change (substitutional bias). This finding suggests caution should be exercised in the interpretation of nucleotide sequence analyses that appear to favor the view of a common endosymbiont for the cyanelle and chlorophyll-b-containing chloroplasts. The data and approaches needed to resolve the issue of cyanelle origins are discussed. Our findings also have general implications for phylogenetic inference under conditions where the base compositions (compositional bias) of the sequences analyzed differ.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00182392
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    The effects of ultraviolet irradiation on P680+ reduction in PS II core complexes measured for individual S-states and during repetitive cycling of the oxygen-evolving complex (1996)
    Springer
    Photosynthesis research 49 (1996), S. 21-27 
    Details
    ISSN: 1573-5079
    Keywords: Photosystem II core complex ; P680+ reduction kinetics ; S-state ; ultraviolet radiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Flash-induced absorbance measurements at 830 nm on both nanosecond and microsecond timescales have been used to characterise the effect of ultraviolet light on Photosystem II core particles. A combination of UV-A and UV-B, closely simulating the spectrum of sunlight below 350 nm, was found to have a primary effect on the donor side of P680. Repetitive measurements indicated reductions in the nanosecond components of the absorbance decay with a concomitant appearance and increase in the amplitude of a component with a 10 μs time constant attributed to slow reduction of P680+ by Tyrz when the function of the oxygen evolving complex is inhibited. Single-flash measurements show that the nanosecond components have amplitudes which vary with S-state. Increasing UV irradiation inhibited the amplitude of these components without changing their S-state dependence. In addition, UV irradiation resulted in a reduction in the total amplitude, with no change in the proportion of the 10 μs contribution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00029424
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    P680+ reduction in oxygen-evolving Photosystem II core complexes (1996)
    Springer
    Photosynthesis research 49 (1996), S. 209-221 
    Details
    ISSN: 1573-5079
    Keywords: Photosystem II ; core particle ; P680 ; 830 nm transient absorption ; S-states ; oxygen-evolving complex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The kinetics of P680+ reduction in oxygen-evolving spinach Photosystem II (PS II) core particles were studied using both repetitive and single-flash 830 nm transient absorption. From measurements on samples in which PS II turnover is blocked, we estimate radical-pair lifetimes of 2 ns and 19 ns. Nanosecond single-flash measurements indicate decay times of 7 ns, 40 ns and 95 ns. Both the longer 40 ns and 95 ns components relate to the normal S-state controlled Yz → P680+ electron transfer dynamics. Our analysis indicates the existence of a 7 ns component which provides evidence for an additional process associated with modified interactions involving the water-splitting catalytic site. Corresponding microsecond measurements show decay times of 4 μs and 90 μs with the possibility of a small component with a decay time of 20–40 μs. The precise origin of the 4 μs component remains uncertain but appears to be associated with the water-splitting center or its binding site while the 90 μs component is assigned to P680+-QA − recombination. An amplitude and kinetic analysis of the flash dependence data gives results that are consistent with the current model of the oxygen-evolving complex.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00034782
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    Paper (German National Licenses)
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