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Biological specimen preparation; Biological techniques and instruments; Drying; Electron microscope examination of materials; Electron microscopy; Freezing; Macromolecules; Molecular biophysics; Proteins; Cryogenics [A0720M]; Electron and ion microscopes and techniques [A0780]; Biophysical instrumentation and techniques [A8780]
Abstract:
A rapid cooling/cryotransfer system was designed to achieve a high reproducibility in vitrifying thin water films containing biological specimens. In order to improve the contrast these unstained specimens were deliberately freeze-dried in situ in the electron microscope. The preservation of the structure obtained by freeze-drying at 180K and subsequent microscopy at 90K is very encouraging as has been shown with two types of test specimen. Tubular photosynthetic membranes were used to examine the effects of a variety of freeze-drying conditions on structural preservation, as judged by flattening of the tubes. A two-dimensional protein crystal was used to evaluate problems of low-dose microscopy of unstained, freeze-dried proteins. The radiation sensitivity of the unstained, freeze-dried protein crystal was investigated by a dose series covering a wide range. (17 References).
