| 1. |
- Kvashnina, K., et al.
(författare)
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Electron transfer during selenium reduction by iron surfaces in aqueous solution: high resolution X-ray absorption study
- 2009
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Ingår i: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 190:012191, s. 1-4
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Tidskriftsartikel (refereegranskat)abstract
- In several designs proposed by different countries, high-level radioactive waste will be disposed in a canister with a copper outer container and a cast iron or carbon steel insert. If the iron insert comes into contact with anoxic geological water, anaerobic corrosion could take place and release fission products such as 79Se to the biosphere. This paper present studies of the long-term kinetics of selenate (SeO42-) in the presence of iron surface under anaerobic conditions by Near Edge X-ray Absorption Spectroscopy (XANES). Substantial changes in the selenium oxidation state is found and discussed in details. We assume that such behaviour corresponds to the electron transfer from iron to selenium, which couldn't take place on oxidized iron surface. When selenate was in contact with polish steel foil in groundwater solution, reduction of Se and formation of Se(II-)was found. These findings suggest that depending of corroded or oxidised iron surface, the selenium mobility in nuclear waste disposal systems will be different.
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| 4. |
- Yano, J, et al.
(författare)
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X-ray damage to the Mn4Ca complex in single crystals of photosystem II: : A case study for metalloprotein crystallography
- 2005
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - , Phys Biosci Div, Melvin Calvin Lab, Berkeley, CA 94720 USA. Univ Calif Berkeley, Dept Chem, Berkeley, CA 94720 USA. Tech Univ Berlin, Max Volmer Lab Biophys Chem, D-10623 Berlin, Germany. Stanford Synchrotron Radiat Lab, Stanford, CA 94305 USA. European Synchrotron Radiat Facil, F-38043 Grenoble, France. Free Univ Berlin, Inst Kristallog, D-14195 Berlin, Germany. Max Planck Inst Bioanorgan Chem, D-45470 Mulheim, Germany. : NATL ACAD SCIENCES. - 0027-8424 .- 1091-6490. ; 102:34, s. 12047-12052
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Tidskriftsartikel (refereegranskat)abstract
- X-ray absorption spectroscopy was used to measure the damage caused by exposure to x-rays to the Mn4Ca active site in single crystals of photosystem II as a function of dose and energy of x-rays, temperature, and time. These studies reveal that the conditions used for structure determination by x-ray crystallography cause serious damage specifically to the metal-site structure. The x-ray absorption spectra show that the structure changes from one that is characteristic of a high-valent Mn-4(III2,IV2), oxo-bridged Mn4Ca cluster to that of Mn(II) in aqueous solution. This damage to the metal site occurs at a dose that is more than one order of magnitude lower than the dose that results in loss of diffractivity and is commonly considered safe for protein crystallography. These results establish quantitative x-ray dose parameters that are applicable to redox-active metalloproteins. This case study shows that a careful evaluation of the structural intactness of the active site(s) by spectroscopic techniques can validate structures derived from crystallography and that it can be a valuable complementary method before structure-function correlations of metalloproteins can be made on the basis of high-resolution x-ray crystal structures.
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