| 日時: |
2003-05-29 15:30 - 16:30 |
| 場所: |
4号館 2階 輪講室１ |
| 会議名: |
放射光セミナー「X-ray Absorption Spectroscopy: From Biology to Archaeology」 |
| 講演者: |
Prof. Farideh Jalilehvand (University of Calgary, Canada) |
| 講演言語: |
英語 |
| URL: |
http://pfwww.kek.jp/pf-seminar/ |
| アブストラクト: |
Synchrotron-based X-ray absorption spectroscopy (XAS) is an element specific, non-destructive technique revealing the local structure around an absorbing atom, even in low concentration. The X-ray absorption near edge structure (XANES) provides information on the oxidation state, electronic configuration and bonding of the absorber, and has recently been explored for speciation in natural samples of some environmentally important elements, such as sulfur. The extended X-ray absorption fine structure (EXAFS) yields bond distances, type and number of coordinating atoms.
For modeling the active site in the sulfite oxidase family of enzymes, three Mo(V,VI) monodithiolene complexes were characterized by XAS methods. By comparing with XANES and EXAFS data of chicken sulfite oxidase, the Mo(VI) complex, [MoO2(SC6H2-2,4,6,Pri3)(bdt)]1- (bdt= benzene-1,2-dithiolate), was found to be an accurate structural analogue of the oxidized site of this enzyme.
Sulfur speciation is essential to connect the effects of sour gas exposure to the sulfur metabolism in plants. Analyses of sulfur XANES spectra of fresh, intact plant leaves from several locations in California and near a sour gas source in Alberta, show different types of sulfur species, from cysteine -SH groups to sulfate, in the leaves.
Sulfur XANES was also used to find the origin of a severe conservation problem for wooden marine-archaeological artifacts, first expressed as sulfate salt formation on soft wood for the 17th century Swedish shipwreck Vasa in the Vasa Museum, Stockholm. We could conclude that a large amount of sulfur had accumulated in reduced forms, mostly elemental sulfur, and was being oxidized to sulfuric acid in the moist wood, causing wood deterioration.1 1 M. Sandstr醇r, F. Jalilehvand, I. Persson, U. Gelius, P. Frank and I. Hall-Roth, Nature 2002, 415, 893-897. |
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