High Resolution 3D X-ray Diffraction Microscope

提出了通过扩展形式的X射线晶体学（或等效地开发和使用用于细胞生物学的软X射线衍射显微镜）对小细胞进行三维成像。 该仪器旨在提供分辨率优于20 nm的冷冻水合细胞和亚细胞结构的三维图像。 该仪器不使用光学元件来形成图像，而是记录相干照明物体的衍射图案，并使用从晶体学借来的技术，使用迭代算法进行重建。 这样，分辨率就不受光学器件的限制，未来的发展应该进一步提高分辨率极限。 来自非晶体样品的衍射图案是连续的（斑点）图案。 与晶体的情况不同，这种模式包含足够的信息，通过以更精细的尺度对衍射图案进行采样来克服晶体学的相位问题。在国家同步加速器光源的波荡器辐射用于提供样品的相干照明。 使用CCD检测器记录衍射图案。 要特别注意保护探测器不受除所需信息以外的所有信息的影响。 单个图案产生二维图像。为了获得三维重建的样本旋转和一组衍射图案被收集。 冷冻的含水标本用于尽量减少辐射损伤的影响。

The three dimensional imaging of a small cell by an extended form of X-ray crystallography (or equivalently the development and use of a soft X-ray diffraction microscope for use in cell biology) is proposed. This instrument is designed to provide three-dimensional images of frozen hydrated cellular and sub-cellular structures at better than 20 nm resolution. The instrument does not use optical elements to form the image instead it records the diffraction pattern of the coherently illuminated object, and using techniques borrowed from crystallography, performs the reconstruction using an iterative algorithm. This way the resolution is not limited by the optics, and future developments should improve the resolution limit further. The diffraction pattern from a non-crystalline specimen is a continuous (speckle) pattern. Unlike the case with crystals this pattern contains sufficient information to overcome the phase problem of crystallography by sampling the diffraction pattern at a finer scale. Undulator radiation at the National Synchrotron Light Source is used to provide coherent illumination of the specimen. The diffraction pattern is recorded using a CCD detector. Special care is taken to shield the detector from all but the desired information. A single pattern yields a two-dimensional image. To obtain three-dimensional reconstruction the specimen is rotated and a set of diffraction patterns is collected. Frozen hydrated specimens are used to minimize the effects of radiation damage.