Abstract's Details

Quantitative Analysis of Near-edge X-ray Absorption Spectra Using Model Compounds
Abstract ID	W:XANES-02
Presenter	Graham George
Presentation Type	XANES Workshop
Full Author List	G. N. George (1)
Affiliations	(1) University of Saskatchewan
Category	Bio/Life Sciences
Abstract	X-ray absorption spectroscopy is a powerful technique that can provide information on the chemical environment of an element of interest. The major strength of the technique is that it requires no sample pre-treatment and can thus be applied to provide in situ chemical information a wide range of samples. Analysis of near-edge spectra of samples containing complex mixtures of species using spectra of model compounds is now a well-accepted and reliable technique. The sensitivity and variability of near-edge spectra will be reviewed, and the methods of analysis will be discussed with reference to examples taken from the speaker’s research.
Footnotes
Funding Acknowledgement	Supported by the Natural Sciences Research and Engineering Council (Canada), the Canadian Institutes of Health Research, a Canada Research Chair award and The National Institutes of Health.

Arsenic, Selenium and The World’s Worst Mass Poisoning
Abstract ID	UMTG:7-3
Presenter	Graham George
Presentation Type	SSRL/LCLS
Full Author List	G. N. George (1), I. J.Pickering (1), J. Gailer (2), P. LaPorte (3), J. Spallholtz (4)
Affiliations	(1) University of Saskatchewan (2) University of Calgary (3) University of Chicago (4) Texas Tech University
Category	Environmental Science
Abstract	It has been known for nearly 70 years that a lethal dose of arsenite cancels an equal, and otherwise lethal, dose of selenite. Our X-ray absorption spectroscopy studies have revealed the metabolic reason – a detoxification molecule containing one selenium and one arsenic atom (seleno bis S-glutathionyl arsnium ion) is formed in blood and excreted in the bile. Though interesting, the ramifications of this finding may prove to be much more profound. Widespread contamination of drinking water by arsenic in Bangladesh and nearby parts of India has resulted in what has been called the world’s worst mass poisoning ever, affecting between 30 and 85 million people. We have suggested that, rather than arsenic poisoning, the Bangladeshi arsenicosis is actually a selenium deficiency. The first clinical trial of selenium supplementation in Bangladesh is now in progress, and recent X-ray absorption spectroscopic results will be presented and discussed.
Footnotes
Funding Acknowledgement	Research supported by the Canadian Institutes of Health Research, Natural Sciences and Engineering Resarch Council (Canada), The Canada Research Chairs Program and the National Institutes of Health.

From Ferns to Fish to Frontal Lobes: X-ray Spectroscopy and Microprobe of Heavy Metals in Living Things
Abstract ID	W:MICRO-08
Presenter	Graham George
Presentation Type	Microfocusing Workshop
Full Author List	M. Korbas (1), I. J. Pickering (1), G. N. George (1), H. Nichol (1)
Affiliations	(1) University of Saskatchewan
Category	Bio/Life Sciences
Abstract	X-ray absorption spectroscopy has been proved invaluable in determining the average chemical form of metals or metalloids in intact biological tissues. Because most tissues have spatial structure, there is great additional interest in visualizing the spatial location of the metal or metalloid as well as its chemical forms. Spectroscopic imaging gives the opportunity of producing maps of specific chemical types of elements in vivo in dilute biological systems. X-ray fluorescence microprobe techniques are routinely used to study samples with spatial heterogeneity. Microprobe produces elemental maps, with chemical sensitivity obtained by recording micro-XAS spectra at selected point locations on the map. Unfortunately, using these procedures spatial detail may be lost as the number of point spectra recorded generally is limited. A powerful extension of microprobe is spectroscopic imaging, or chemically specific imaging. Here, the incident energy is tuned to features in the near-edge which are characteristic of the expected chemical forms of the element. With a few simple assumptions, these XAS images can then be converted to quantitative images of specific chemical form, yielding considerable clarity in the distributions. The presentation will draw upon recent examples from our research on spectroscopic imaging and microprobe of biological tissues.
Footnotes
Funding Acknowledgement	Research at the University of Saskatchewan was supported by the Canadian Institutes for Health Research, the Canada Research Chairs program (GNG & IJP), the Natural Sciences and Engineering Research Council (Canada), the National Institutes of Health and the Saskatchewan Health Research Foundation.