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Träfflista för sökning "WFRF:(Korall P) srt2:(1997-1999)"

Sökning: WFRF:(Korall P) > (1997-1999)

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1.
  • Korall, Petra, 1968-, et al. (författare)
  • Phylogeny of selaginellaceae : Evaluation of generic subgeneric relationships based on rbcL gene sequences
  • 1999
  • Ingår i: International journal of plant sciences. - 1058-5893 .- 1537-5315. ; 160:3, s. 585-594
  • Tidskriftsartikel (refereegranskat)abstract
    • A cladistic analysis based on rbcL gene sequences from a representative sample of 18 species yields three most parsimonious trees that strongly support monophyly of Selaginellaceae. Within Selaginellaceae, the morphologically distinctive subgenus Selaginella is resolved as sister group to a clade composed of all other species, here termed the rhizophoric clade. In the rhizophoric clade, subgenus Stachygynandrum is paraphyletic to subgenera Ericetorum, Tetragonostachys, and Heterostachys. Monophyly of Ericetorum and Tetragonostachys is strongly corroborated. Results support a close relationship between "resurrection plants" in Stachygynandrum and the mat-forming or tufted drought-tolerant species of Tetragonostachys, indicating a common origin of xerophytism in these groups. A close relationship for all isophyllous species, as hypothesized in many classifications, is not supported by the rbcL data. Leaf isophylly and reduction in Ericetorum and Tetragonostachys most probably represent independent reversals of the marked anisophyllous condition in Stachygynandrum, Leaf reduction is one of a suite of characters that may have evolved in response to seasonal drought.
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2.
  • Magnuson, Ann, et al. (författare)
  • Mimicking electron transfer reactions in photosystem II: Synthesis and photochemical characterization of a ruthenium(II) tris(bipyridyl) complex with a covalently linked tyrosine
  • 1997
  • Ingår i: Journal of the American Chemical Society. - : The American Chemical Society (ACS). - 1520-5126 .- 0002-7863. ; 119:44, s. 10720-10725
  • Tidskriftsartikel (refereegranskat)abstract
    • In the natural photosynthetic reaction center photosystem II, absorption of a photon leads to photooxidation of the primary electron donor P-680, which subsequently retrieves electrons from a tyrosyl residue, functioning as an interface to the oxygen-evolving manganese complex. In a first step toward mimicking these reactions, we have made a Ru(II)-polypyridine complex with an attached tyrosyl moiety. The photoexcited ruthenium complex played the role of P-680 and was first oxidized by external accepters. Combined transient absorbance and EPR studies provided evidence that the Ru(III) formed was reduced by intramolecular electron transfer from the attached tyrosine, with a rate constant of 5 x 10(4) s(-1). Thus we show that a tyrosine radical could be formed by light-induced electron transfer reactions, and we indicate future directions for developing a closer analogy with the photosystem II reactions.
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4.
  • Sun, L C, et al. (författare)
  • Binuclear ruthenium-manganese complexes as simple artificial models for photosystem II in green plants
  • 1997
  • Ingår i: Journal of the American Chemical Society. - : The American Chemical Society (ACS). - 1520-5126. ; 119:30, s. 6996-7004
  • Tidskriftsartikel (refereegranskat)abstract
    • As part of a project aimed at developing models for photosystem II (PSII) in green plants, we have prepared a series of model compounds (7, 8, and 13). In these compounds, a photosensitizer, ruthenium(II) tris(bipyridyl) complex (to mimic the function of P-680 in PSII), was covalently linked to a manganese(II) ion through different bridging ligands. The structures of the compounds were characterized by electron paramagnetic resonance measurements and electrospray ionization mass spectrometry. The interaction between the ruthenium and manganese moieties within the complex was probed by steady-state and time-resolved emission measurements. When the binuclear complexes are exposed to flash photolysis in the presence of an electron acceptor such as methylviologen (MV2+), it could be shown that after the initial electron transfer from the excited state of Ru(II) in compound 7, forming Ru(III) and MV+., an intramolecular electron transfer from coordinated Mn(II) to the photogenerated Ru(III) occurred with a first-order rate constant of 1.8 x 10(5) s(-1), regenerating Ru(II). This is believed to be the first supramolecular system where a manganese complex has been used as an electron donor to a photo-oxidized photosensitizer, Possible extensions to develop the manganese donor, and thus to approach the function of reaction center in PSII, are indicated.
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