- Conference date: 2-6 Aug 1999
- Location: Berkeley, California (USA)
Soft X-ray microscopy employs the natural absorption contrast between water and protein in the 2.34–4.38 nm wavelength region with a resolution down to 30 nm. The large depth of focus of the Fresnel zone plates used as X-ray objectives permits tomographic reconstruction based on the microscopic images. High-resolution images require a high specimen radiation dose, and a large number of images taken at different viewing angles is needed for tomographic reconstruction. Therefore, cryo microscopy is necessary to preserve the structural integrity of hydrated biological specimens during image acquisition. The cryo transmission X-ray microscope at the electron storage ring BESSY I (Berlin) was used to obtain a tilt series of images of the frozen-hydrated green alga Chlamydomonas reinhardtii. The living specimens were inserted into borosilicate capillaries, then rapidly cooled by plunging into liquid nitrogen. The capillary specimen holders allow image acquisition over the full angular range of 180°. The reconstruction shows details inside the alga down to 60 nm size and conveys a detailed impression of the specimen structure. This technique is expected to be applicable to a wide range of biological specimens, such as the cell nucleus. It offers the possibility of imaging the three-dimensional structure of hydrated biological specimens close to their natural living state.
- Image reconstruction
- Digital image processing
- X-ray microscopes
- X-ray microscopy
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