Cryo X-ray microscopy with high spatial resolution in amplitude and phase contrast
Cryo X-ray microscopy with high spatial resolution in amplitude and phase contrast
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DOI：
10.1016/s0304-3991(98)00054-0
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发表时间：
1998-11-01
期刊：
影响因子：
2.2
通讯作者：
Schneider, G
中科院分区：
文献类型：
--
作者：
Schneider, G
使用波带片光学器件的透射X射线显微镜（TXMs）的分辨率目前约为30nm。理论和实验表明，在辐射敏感的水合生物材料中，利用冲击冷冻样品可以获得这种分辨率。为此目的，X射线与物质的相互作用和波带片的成像被描述。第一次在计算中的图像对比度，光子密度和辐射剂量所需的对象照明的聚光器和波带片物镜的有限孔径的影响。模型的考虑表明，最低的辐射剂量和高的图像对比度，得到优化的相位对比度，利用吸收以及相移。通过辐射诱导动力学定量评价了吸收的X射线的损伤效应，表明低温样品是结构稳定的。为了验证这些理论模型，TXM被修改为允许在大气压下对冷冻水合样品进行成像。在振幅对比模式下，细胞和藻类内部小至35 nm的细节在2.4 nm波长处可见。在此分辨率下，低温样品未显示结构变化。正如预测的那样，优化的相位对比显示了具有高对比度的冷冻水合物体内部的结构。藻类的立体对图像揭示了细胞器的3D组织。整个低温电池的元素分析和显微断层扫描是可能的。(C)1998 Elsevier Science B.V.保留所有权利。
The resolution of transmission X-ray microscopes (TXMs) using zone plate optics is presently about 30 nm. Theory and experiments presented here show that this resolution can be obtained in radiation sensitive hydrated biological material by using shock frozen samples. For this purpose the interaction of X-rays with matter and the image formation with zone plates is described. For the first time the influence of the limited apertures of the condenser and the zone plate objective are in included in calculations of the image contrast, the photon density and radiation dose required for the object illumination. Model considerations show that lowest radiation dose and high image contrast are obtained in optimized phase contrast which exploits absorption as well as phase shift. The damaging effect of the absorbed X-rays is quantitatively evaluated by radiation-induced kinetics showing that cryogenic samples are structurally stable. To verify these theoretical models the TXM was modified to allow imaging of frozen-hydrated samples at atmospheric pressure. Details inside cells and algae as small as 35 nm are visible at 2.4 nm wavelength in amplitude contrast mode. At this resolution the cryogenic samples show no structural changes. As predicted, optimized phase contrast shows structures inside the frozen-hydrated objects with high contrast. Stereo-pair images of algae reveal the 3D organization of the organelles. Element analysis and micro-tomography of whole cryogenic cells are possible. (C) 1998 Elsevier Science B.V. All rights reserved.