XAS AND XAS IMAGING OF ORGANISMS IN THE ENVIRONMENT

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 重元素，如砷和硒，通过自然和人工过程进入环境，然后被生物利用。硒，可能还有砷，是哺乳动物必需的微量元素，但这两种元素的毒性也是众所周知的。任何元素的分子形式都严重影响其运输、生物利用度和毒理学，换句话说，它如何与环境相互作用，并最终与人类相互作用。为了提出有效的补救策略，还需要分子形式的知识。X射线吸收光谱(XAS)可以在根本上研究元素的化学形态，而不需要对样品进行前处理，因此可以获得关于化学形态的原位信息。XAS成像是一种强大的微探针技术，它以对不同化学形态敏感的能量在小光束中对样品进行栅格扫描，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是砷和硒的分子形态和空间位置。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，并提供植物修复的潜力。还将研究简单的昆虫生态系统，以研究单独或与汞结合时，硒是如何生物积累和生物转化的。最后，将对暴露在非致死水平或砷和汞中的斑马鱼幼体进行研究，以确定重元素的定位和形态。拟议的计划应该提供关于重元素，特别是砷和硒在环境中如何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.