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- Shafaat, Hannah S., et al.
(författare)
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Electronic Structural Flexibility of Heterobimetallic Mn/Fe Cofactors : R2lox and R2c Proteins
- 2014
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 136:38, s. 13399-13409
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Tidskriftsartikel (refereegranskat)abstract
- The electronic structure of the Mn/Fe cofactor identified in a new class of oxidases (R2lox) described by Andersson and Hogbom [Proc. Natl. Acad. Sci. U.S.A. 2009, 106, 5633] is reported. The R2lox protein is homologous to the small subunit of class Ic ribonucleotide reductase (R2c) but has a completely different in vivo function. Using multifrequency EPR and related pulse techniques, it is shown that the cofactor of R2lox represents an antiferromagnetically coupled Mn-III/Fe-III dimer linked by a mu-hydroxo/bis-mu-carboxylato bridging network. The Mn-III ion is coordinated by a single water ligand. The R2lox cofactor is photoactive, converting into a second form (R2lox(photo)) upon visible illumination at cryogenic temperatures (77 K) that completely decays upon warming. This second, unstable form of the cofactor more closely resembles the Mn-III/Fe-III cofactor seen in R2c. It is shown that the two forms of the R2lox cofactor differ primarily in terms of the local site geometry and electronic state of the Mn-III ion, as best evidenced by a reorientation of its unique Mn-55 hyperfine axis. Analysis of the metal hyperfine tensors in combination with density functional theory (DFT) calculations suggests that this change is triggered by deprotonation of the mu-hydroxo bridge. These results have important consequences for the mixed-metal R2c cofactor and the divergent chemistry R2lox and R2c perform.
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- Wallenhammar, Ann-Charlotte, et al.
(författare)
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Clubroot, a persistent threat to Swedish oilseed rape production
- 2014
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Ingår i: Canadian Journal of Plant Pathology. - : Informa UK Limited. - 0706-0661 .- 1715-2992. ; 36, s. 135-141
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Tidskriftsartikel (refereegranskat)abstract
- Brassica oilseed crops have been grown by Swedish farmers since the early 1940s. Years of high market prices for vegetable oils resulted in intensive cultivation of Brassica oilseeds in various regions, which led to problems with soilborne pathogens including Plasmodiophora brassicae. This pathogen most likely was present in Swedish soils prior to the Brassica oilseed boom after World War II. Currently, reports of clubroot disease outbreaks in Sweden are frequent, with a trend of increasing incidence. Since 2012, DNA-based soil analyses for the presence of P. brassicae have been offered to farmers in order to improve their crop rotation planning. Other means of limiting the damage caused by P. brassicae also are presently under study, such as the effects of boron or different sources of nitrogen. The distribution and identification of different pathotypes/races of P. brassicae in Sweden could so far not be verified. To aid in race diagnostics, resistance breeding efforts, and in understanding the biology of this Plasmodiophorid, the sequencing of the P. brassicae genome has been initiated in Sweden.
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