Synchrotron studies of selenium environmental chemistry

环境中的硒。作为所有生命王国所必需的微量元素，硒是地壳中含量最少的微量元素之一。世界硒的分布变化很大；虽然加拿大的草原土壤是生产高硒作物最丰富的土壤之一，但全球土壤更有可能提供不足的硒。此外，硒在充足和过量的饮食量之间的差异可能比任何其他元素都小。由于采矿或其他人为活动，加拿大几个地区的水环境中硒含量略有升高，这引起了人们越来越多的关注，因为硒的生物积累会给顶级捕食者带来问题。在不足和过剩之间保持微妙的平衡只是Se面临的挑战之一。****有机体中的硒。第21种氨基酸硒代半胱氨酸存在于谷胱甘肽过氧化物酶等关键酶的活性位点。此外，硒与汞、砷和镉等有毒元素具有神秘的生物相互作用。虽然一些硒的化学形式可以防止这些元素，但在其他情况下，硒会增加毒性。虽然前者至少部分被理解，但后者的机制仍然是一个谜。* * * * * *的目标。该计划寻求在环境和影响人类健康的分子水平上硒的作用和相互作用的整体观点。了解硒的化学形态是了解其功能和影响的关键，无论是有害的，良性的还是有益的。* * * * * *科学方法。在职业贡献的基础上，该计划将使用和开发同步加速器技术，与研究界分享改进，特别是在加拿大光源BioXAS光束线，申请人是科学共同领导。x射线吸收光谱提供物种形成的信息，而x射线荧光成像产生微观元素分布的生物样品很少预处理。研究将包括纯化生物分子的结构表征，以确定硒的功能。其他项目将研究硒在植物和动物模型中的分布、化学形式和与其他元素的相互作用，以了解潜在的机制。******培训。通过跨学科项目培训的高素质人员使用和开发专门的同步加速器工具，将更善于适应技术来解决问题，使他们能够从事高知名度的职业。* * * * * *战略相关性。加拿大大草原的高土壤硒导致作物富含硒，潜在地增加了它们的营养价值。相反，采矿径流中硒含量的略微升高可能会造成环境问题。硒的正面和负面都有重大的经济影响。这项工作促进了对硒在生物体中的对比作用的理解，对于评估加拿大硒的积极和消极方面至关重要。**

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. **