Nanoprobe for High Resolution Hard X-ray Fluorescence Microscopy

描述(由申请人提供)：用于高分辨率硬X射线荧光显微镜的纳米探测器(供应商X-Radia)为了促进我们对细胞和组织中天然金属动态平衡的了解，以及详细了解纳米材料在细胞和组织中的定位、定量和化学状态，我们建议购买和安装一台具有低温能力的高分辨率(30 nm范围)硬X射线荧光纳米探测器，以便对生物标本进行研究。该仪器将从X-Radia公司购买，并安装在阿贡国家实验室(ANL)高级光子源(APS)的生命科学协作访问小组(LS-CAT)的光束线上。由于需要高亮度的X射线，APS同步加速器是美国唯一可以使用纳米探测器的地方(也是全世界仅有的三个地方之一)。LS-CAT的主要科学家以及LS-CAT合作机构的调查人员表达了他们对安装生物纳米探测器的支持。同时，APS其他部门(XOR部门2)的X射线荧光专家将致力于安装和运行NanoProbe，并为本提案中所列X射线荧光显微镜(XFM)的未来和当前用户提供帮助。在这项提案中列出的19名NIH资助的研究人员与许多其他人一起对纳米探测器将提供的30纳米分辨率水平的XFM技术感兴趣。虽然我们已经列出了NIH资助的研究人员名单，但我们还有一个NSF和美国能源部资助的研究人员名单，他们也将有兴趣使用该仪器研究细菌、环境样本等中的金属含量。这项提议的目的是购买和安装具有优化的光学系统、高效探测器、样品定位工具和低温样品环境的硬X射线生物纳米探头。该仪器将能够进行显微镜、显微光谱和光谱显微镜技术(5-XANES)和断层成像，重点是对生物样品中的痕量元素含量进行X射线荧光分析。样品的X射线诱导X射线荧光揭示了单个元素的空间分布和数量。由于X射线探头的灵敏度比电子探头高出约1000倍，因此荧光技术是定量痕量元素分析的有力工具。例如，在30纳米的空间分辨率(比光学显微镜的最大分辨率高10倍)下，纳米探测器只能探测到数十个锌原子。通过对样品的吸收对比度进行透射式成像，可以绘制出样品的电子密度和质量密度图。在光谱学模式下，初级X射线束的能量被扫描穿过元素的吸收边缘，提供关于其化学状态(XANES)或其局部环境(EXAFS)的信息。最后，在X射线层析成像中，产生一系列的二维投影图像，并将它们组合起来重建样品的内部三维结构。这对于观察亚细胞结构和确定细胞细胞器的元素定位特别重要。

DESCRIPTION (provided by applicant): Nanoprobe for High Resolution Hard X-ray Fluorescence Microscopy (vendor X-Radia) In the interest of advancing our understanding of natural metal homeostasis in cells and tissues, as well as to detail localization, quantitation and chemical states of nanomaterials in cells and tissues, we propose to purchase and install a high resolution (30 nm range) hard X-ray fluorescence Nanoprobe with cryogenic capabilities that would allow studies of biological specimens. This instrument will be purchased from X- Radia and installed at the beamline of the Life Sciences Collaborative Access Team (LS-CAT) at the Advanced Photon Source (APS) at Argonne National Laboratory (ANL). The APS synchrotron is the only place in the USA (and one of the only three places in the entire world) where the Nanoprobe could be used because of the need for X-rays of high brilliance. The leading scientists at LS-CAT as well as investigators from LS-CAT partner institutions expressed their support for housing the Bio-Nanoprobe. At the same time, X-ray fluorescence experts from the other sections of APS (XOR sector 2) are committed to install and run the Nanoprobe, and aid future and current users of X-ray fluorescence microscopy (XFM) listed in this proposal. Nineteen NIH funded investigators listed on this proposal are joined by many others in their interest for XFM technique at the resolution level of 30nm which Nanoprobe will provide. While we have listed NIH funded investigators, we have an additional list of NSF- and DOE-funded investigators who would also be interested in using the instrument for studies of metal content in bacteria, environmental samples, etc. The aim of this proposal is to purchase and install a hard X-ray Bio-Nanoprobe with optimized optics, efficient detectors, tools for specimen positioning and cryogenic specimen environment. This instrument will be capable of microscopy, micro-spectroscopy and spectro-microscopy techniques (5- XANES), and tomography, with an emphasis on X-ray fluorescence analysis of trace elemental content in biological samples. X-ray induced X-ray fluorescence from the sample reveals the spatial distribution and quantity of individual elements. Because an X-ray probe can offer up to ~1000 times higher sensitivity than electron probes, the fluorescence technique is a powerful tool for quantitative trace-element analysis. At a spatial resolution of 30 nm (10x better than the maximal resolution of optical microscopes), the Nanoprobe would detect as little as tens of atoms of zinc, for example. Using transmission mode imaging the absorption contrast of the sample, its electron and mass density can be mapped. In spectroscopy mode, the primary X-ray beam's energy is scanned across the absorption edge of an element, providing information on its chemical state (XANES) or its local environment (EXAFS). Finally, in X-ray tomography, a series of 2-D projection images is produced and they are combined to reconstruct the sample's internal 3-D structure. This will be particularly important for observing subcellular structures and determining the elemental localization with respect to cell organelles.