Low-temperature x-ray microscopy of biological samples in amplitude and phase contrast

Gerd Schneider; Bastian Niemann; Peter Guttmann; Guenther A. Schmahl

doi:10.1117/12.330331

6 November 1998 Low-temperature x-ray microscopy of biological samples in amplitude and phase contrast

Gerd Schneider, Bastian Niemann, Peter Guttmann, Guenther A. Schmahl

Proceedings Volume 3449, X-Ray Microfocusing: Applications and Techniques; (1998) https://doi.org/10.1117/12.330331
Event: SPIE's International Symposium on Optical Science, Engineering, and Instrumentation, 1998, San Diego, CA, United States

Abstract

X-ray microscopy provides higher resolution than optical microscopy and higher penetration power than electron microscopy. Therefore, x-ray microscopy allows high resolution imaging of thick hydrated samples. The two dominating processes determining the contrast in x-ray microscopy are photoelectric absorption and phase shift. Phase contrast is especially suited to visualize features in hydrated cells with low natural amplitude contrast. Living cells are damaged by ionizing radiation, e.g. soft x-rays. For this reason an object stage for cryogenic specimen was developed and implemented on the Goettingen transmission x-ray microscope at the electron storage ring BESSY. It allows objects to be imaged at temperatures below 120 K in cryogenic nitrogen gas at atmospheric pressure. This system was used to perform experiments with initially living biological objects, e.g. cells, algae and chromosomes. The preparation of the sample only comprised shock freezing in liquid ethane to cryogenic temperatures. The structural stability of these frozen-hydrated samples is increased by about four orders of magnitude compared to unfixed wet specimens at room temperatures. For this reason micro-tomography is possible with high spatial resolution, which reveals the 3D morphology, e.g. the 3D distribution of organic compounds, close to the natural, functional state. In addition, cryo x-ray microscopy will also allow investigations of kinetic processes. The cooling time to produce a vitrified sample is on the order of a millisecond, thus an active process in a cell can be stopped by freezing at a well defined state.

Citation Download Citation

Gerd Schneider, Bastian Niemann, Peter Guttmann, and Guenther A. Schmahl "Low-temperature x-ray microscopy of biological samples in amplitude and phase contrast", Proc. SPIE 3449, X-Ray Microfocusing: Applications and Techniques, (6 November 1998); https://doi.org/10.1117/12.330331

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