title: Selenium metabolism in cancer cells: the combined application of XAS and XFM techniques to the problem of selenium speciation in biological systems.
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.
authors.affiliation: School of Chemistry and Physics, The University of Adelaide, Adelaide, SA 5005, Australia. claire.weekley@adelaide.edu.au
authors.forename: Claire M
authors.initials: CM
authors.lastname: Weekley
authors.forename: Jade B
authors.initials: JB
authors.lastname: Aitken
authors.forename: Lydia
authors.initials: L
authors.lastname: Finney
authors.forename: Stefan
authors.initials: S
authors.lastname: Vogt
authors.forename: Paul K
authors.initials: PK
authors.lastname: Witting
authors.forename: Hugh H
authors.initials: HH
authors.lastname: Harris
mesh_terms: D000818:Animals; D003300:Copper / Q000378:metabolism; D005453:Fluorescence; D006801:Humans; D008856:Microscopy, Fluorescence / Q000379:methods; D009369:Neoplasms / Q000378:metabolism*; D016566:Organoselenium Compounds / Q000378:metabolism; D012643:Selenium / Q000378:metabolism*; D017279:Selenocysteine / Q000031:analogs & derivatives* / Q000378:metabolism; D012645:Selenomethionine / Q000378:metabolism*; D018038:Sodium Selenite / Q000378:metabolism*; D056928:X-Ray Absorption Spectroscopy / Q000379:methods
chemical_list: D016566:Organoselenium Compounds; D017279:Selenocysteine; D003300:Copper; D012645:Selenomethionine; D012643:Selenium; D018038:Sodium Selenite; C002979:selenomethylselenocysteine