Alteration of the H-bond to the A(1A) phylloquinone in Photosystem I: influence on the kinetics and energetics of electron transfer (Articolo in rivista)

Type
Label
  • Alteration of the H-bond to the A(1A) phylloquinone in Photosystem I: influence on the kinetics and energetics of electron transfer (Articolo in rivista) (literal)
Anno
  • 2011-01-01T00:00:00+01:00 (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#doi
  • 10.1021/jp109531b (literal)
Alternative label
  • Srinivasan N, Santabarbara S, Rappaport F, Carbonera D, Redding K, van der Est A, Golbeck JH. (2011)
    Alteration of the H-bond to the A(1A) phylloquinone in Photosystem I: influence on the kinetics and energetics of electron transfer
    in The journal of physical chemistry. B
    (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#autori
  • Srinivasan N, Santabarbara S, Rappaport F, Carbonera D, Redding K, van der Est A, Golbeck JH. (literal)
Pagina inizio
  • 1751 (literal)
Pagina fine
  • 1759. (literal)
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  • http://pubs.acs.org/doi/abs/10.1021/jp109531b (literal)
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  • 115 (literal)
Rivista
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  • 8 (literal)
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  • 8 (literal)
Note
  • ISI Web of Science (WOS) (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#affiliazioni
  • Department of Biochemistry and Molecular Biology. Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States Institut de Biologie Physico-Chimique, UMR 7141 CNRS/UPMC, 13 Rue Pierre et Marie Curie, 75005 Paris, France Department of Chemical Sciences, University of Padua, Via Marzolo 1, 35131 Padova, Italy Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287, United States Department of Chemistry, Brock University, 500 Glenridge Avenue, St. Catharines, Ontario L2S 3A1, Canada (literal)
Titolo
  • Alteration of the H-bond to the A(1A) phylloquinone in Photosystem I: influence on the kinetics and energetics of electron transfer (literal)
Abstract
  • In Photosystem I, the backbone nitrogen of Leu722(PsaA) forms a hydro-gen bond with the C(4) carbonyl oxygen of phylloquinone in the A(1A) site. A previous low-temperature EPR study indicated that substitution of Leu722(PsaA) with a bulky Trp residue results in a weakened H-bond. Here, we employ room temperature, time-resolved optical spectroscopy and variable temperature, transient EPR spectroscopy to probe the effect of the altered H-bond on the energetics and kinetics of electron transfer. Relative to the wild type, we find that the rate of electron transfer from A(1A)(-) to F(X) in the L722W(PsaA) variant is faster by a factor of 3. This change is attributed to a lowered midpoint potential of A(1A)/A(1A)(-), resulting in a larger Gibbs free energy change between A(1A)/A(1A)(-) and F(X)/F(X)(-). An activation energy of 180±10 meV is determined for the A(1A)(-)-to-F(X) forward electron transfer step in the L722W(PsaA) variant compared with 220±10 meV in the wild type. The Arrhenius plot shows a break at ~200 K, below which the rate becomes nearly independent of temperature. This behavior is described using a quantum mechanical treatment that takes the zero-point energy into account as well as an alternative model that invokes a dynamical transition in the protein at ~200 K. (literal)
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