Synchrotron studies of selenium environmental chemistry

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Selenium in the environment. As a micronutrient element required for all kingdoms of life, selenium (Se) is one of the least abundant micronutrients in the earth's crust. World Se distribution is highly variable; while Canada's prairie soils are among the richest yielding higher Se crops, globally soils are more likely to provide inadequate Se. Moreover, Se has a smaller difference between sufficient and excess dietary amounts than perhaps any other element. There is growing concern over slightly elevated Se in aqueous environments in several areas of Canada due to mining or other anthropogenic activities, since bioaccumulation of Se can cause problems for top predators. This delicate balance between insufficient and excess is just one challenge of Se.****Selenium in organisms. The twenty-first amino acid selenocysteine occurs in active sites of key enzymes such as glutathione peroxidase. In addition Se has enigmatic biological interactions with toxic elements including mercury, arsenic and cadmium. While some Se chemical forms can protect against such elements, in other scenarios Se can increase toxicity. Although the former is at least partly understood, the latter mechanisms remain a mystery. ******Objectives. The program seeks a holistic view of the roles and interactions of Se at the molecular level both in the environment and in impacting human health. Knowing the chemical form of Se is key to understanding its function and impact, whether detrimental, benign or beneficial. ******Scientific approach. Building upon career contributions, the program will use and develop synchrotron techniques, sharing refinements with the research community especially at the Canadian Light Source BioXAS beamlines where the applicant is scientific co-lead. X-ray absorption spectroscopy provides speciation information while X-ray fluorescence imaging yields microscopic elemental distributions in biological samples with little pretreatment. Studies will include structural characterization of purified biomolecules to determine Se functions. Other projects will address Se distribution, chemical forms and interactions with other elements in plants and animal models in order to understand underlying mechanisms.******Training. Highly qualified personnel trained through cross-disciplinary projects to use and develop specialized synchrotron tools will be more generally adept at adapting technologies to solve problems, positioning them for high profile careers.******Strategic relevance. High soil Se in Canada's prairies leads to crops rich in Se, potentially increasing their nutritional value. Conversely, slightly elevated Se in mining runoff can be environmentally problematic. Both positive and negative faces of Se have significant economic consequences. This work advances understanding of Se's contrasting roles in living organisms, essential in assessing both positive and negative aspects of Se in Canada. **