XAS AND XAS IMAGING OF ORGANISMS IN THE ENVIRONMENT

本子项目是利用由NIH/NCRR资助的中心赠款提供的资源的众多研究子项目之一。子项目和研究者（PI）可能已经从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。列出的机构是中心的，不一定是研究者的机构。砷和硒等重元素通过自然和人为过程进入环境，然后为生物所利用。硒，可能还有砷，是哺乳动物必需的微量元素，但两者的毒性也是众所周知的。任何元素的分子形式都会严重影响其运输、生物利用度和毒理学，换句话说，它如何与环境相互作用，最终与人相互作用。为了提出有效的修复策略，还需要了解分子形态。x射线吸收光谱（XAS）可以研究元素的化学形式，基本上不需要对样品进行预处理，因此可以获得有关化学形式的原位信息。XAS成像是一种强大的微探针技术，在这种技术中，样品在对不同化学形式敏感的能量下在小光束中进行光栅扫描，以便生成这些物种的地图。XAS和XAS成像将用于研究与环境相关的生物中主要砷和硒的分子形式和空间位置。在一组实验中，将研究超积累植物的分子机制；这些植物在其组织中吸收和储存高水平的砷或硒，并提供了植物修复的潜力。简单的昆虫生态系统也将被研究，以研究硒是如何生物积累和生物转化的，无论是单独还是与汞结合。最后，将研究暴露于非致死水平或砷和汞的斑马鱼幼虫，以确定重元素的定位和形态。拟议的项目应该提供关于重元素，特别是砷和硒，如何在环境中进行化学转化的有价值的信息。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Heavy elements such as arsenic and selenium enter the environment through natural and manmade processes and then become available to living things. Selenium, and possibly also arsenic, is an essential trace element for mammals, but both are also well known for their toxicity. The molecular form of any element critically affects its transport, bioavailability and toxicology, in other words how it interacts with the environment and ultimately with man. Knowledge of molecular form is also required in order to propose effective remediation strategies. X-ray absorption spectroscopy (XAS) can investigate the chemical form of an element essentially without pretreatment of the sample, and hence can yield in situ information about chemical form. XAS imaging is a powerful microprobe technique in which the sample is raster scanned in a small beam at energies sensitive to the different chemical forms in order to generate maps of those species. XAS and XAS imaging will be used to investigate the molecular form and spatial location of predominantly arsenic and selenium in organisms with environmental relevance. In one set of experiments, the molecular mechanisms of hyperaccumulating plants will be studied; these plants take up and store high levels of arsenic or selenium in their tissues and offer potential for phytoremediation. Simple insect ecosystems will also be studied, to examine how selenium is bioaccumulated and biotransformed, either alone or in combination with mercury. Finally, zebrafish larvae exposed to non-lethal levels or arsenic and mercury will be studied to determine the localization and speciation of the heavy elements. The proposed program should provide valuable information on how heavy elements, and arsenic and selenium in particular, are chemically transformed within the environment.