Deng Junjing, Vine David J, Chen Si, Nashed Youssef S G, Jin Qiaoling, Phillips Nicholas W, Peterka Tom, Ross Rob, Vogt Stefan, Jacobsen Chris J
Applied Physics, Northwestern University, Evanston, IL 60208;
X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439;
Proc Natl Acad Sci U S A. 2015 Feb 24;112(8):2314-9. doi: 10.1073/pnas.1413003112. Epub 2015 Feb 9.
Trace metals play important roles in normal and in disease-causing biological functions. X-ray fluorescence microscopy reveals trace elements with no dependence on binding affinities (unlike with visible light fluorophores) and with improved sensitivity relative to electron probes. However, X-ray fluorescence is not very sensitive for showing the light elements that comprise the majority of cellular material. Here we show that X-ray ptychography can be combined with fluorescence to image both cellular structure and trace element distribution in frozen-hydrated cells at cryogenic temperatures, with high structural and chemical fidelity. Ptychographic reconstruction algorithms deliver phase and absorption contrast images at a resolution beyond that of the illuminating lens or beam size. Using 5.2-keV X-rays, we have obtained sub-30-nm resolution structural images and ∼90-nm-resolution fluorescence images of several elements in frozen-hydrated green algae. This combined approach offers a way to study the role of trace elements in their structural context.
痕量金属在正常和致病生物学功能中发挥着重要作用。X射线荧光显微镜可揭示痕量元素，且不依赖于结合亲和力（与可见光荧光团不同），相对于电子探针具有更高的灵敏度。然而，X射线荧光对于显示构成细胞大部分物质的轻元素并不十分敏感。在此，我们表明X射线叠层成像可以与荧光相结合，在低温下对冷冻水合细胞中的细胞结构和痕量元素分布进行成像，具有高结构和化学保真度。叠层成像重建算法可提供相位和吸收对比图像，其分辨率超过照明透镜或光束尺寸。使用5.2 keV的X射线，我们获得了冷冻水合绿藻中几种元素的亚30纳米分辨率结构图像和约90纳米分辨率荧光图像。这种联合方法为研究痕量元素在其结构背景中的作用提供了一种途径。
