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  • Selenium metabolism in cancer cells: the combined application of XAS and XFM techniques to the problem of selenium speciation in biological systems.

Selenium metabolism in cancer cells: the combined application of XAS and XFM techniques to the problem of selenium speciation in biological systems.

Nutrients (2013-05-24)
Claire M Weekley, Jade B Aitken, Lydia Finney, Stefan Vogt, Paul K Witting, Hugh H Harris
ABSTRACT

Determining the speciation of selenium in vivo is crucial to understanding the biological activity of this essential element, which is a popular dietary supplement due to its anti-cancer properties. Hyphenated techniques that combine separation and detection methods are traditionally and effectively used in selenium speciation analysis, but require extensive sample preparation that may affect speciation. Synchrotron-based X-ray absorption and fluorescence techniques offer an alternative approach to selenium speciation analysis that requires minimal sample preparation. We present a brief summary of some key HPLC-ICP-MS and ESI-MS/MS studies of the speciation of selenium in cells and rat tissues. We review the results of a top-down approach to selenium speciation in human lung cancer cells that aims to link the speciation and distribution of selenium to its biological activity using a combination of X-ray absorption spectroscopy (XAS) and X-ray fluorescence microscopy (XFM). The results of this approach highlight the distinct fates of selenomethionine, methylselenocysteine and selenite in terms of their speciation and distribution within cells: organic selenium metabolites were widely distributed throughout the cells, whereas inorganic selenium metabolites were compartmentalized and associated with copper. New data from the XFM mapping of electrophoretically-separated cell lysates show the distribution of selenium in the proteins of selenomethionine-treated cells. Future applications of this top-down approach are discussed.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Selenium, powder, −100 mesh, ≥99.5% trace metals basis
Sigma-Aldrich
Selenium, pellets, <5 mm, ≥99.99% trace metals basis
Sigma-Aldrich
Selenium, pellets, <5 mm particle size, ≥99.999% trace metals basis
Sigma-Aldrich
Selenium, powder, −100 mesh, 99.99% trace metals basis
Selenium, pellets, < 5mm, ≥99.999%
Selenium, foil, 25x25mm, thickness 3mm, 99.95%