Sample Preparation Handbook for Transmission Electron Microscopy by Jeanne Ayache Luc Beaunier Jacqueline Boumendil Gabrielle Ehret & Danièle Laub

Author:Jeanne Ayache, Luc Beaunier, Jacqueline Boumendil, Gabrielle Ehret & Danièle Laub
Language: eng
Format: epub
Publisher: Springer New York, New York, NY

Like water, ice is capable of migrating if the frozen system is not maintained at a temperature low enough to prevent the diffusion phenomenon. For pure water above 140 K, ice crystals are able to become larger, slowly at first, and then quickly as the temperature rises to around 200 K. Then cubic ice crystals appear. This is in the neighborhood of the Tg of vitreous ice (between 120 and 140 K). In a biological-type heterogeneous system (whose diffusion rate is low), experience shows that this phenomenon occurs around 183 K.

Once water is frozen in the best possible way, one of three preparation pathways can be carried out to observe the sample.

If the sample is made up of small fine particles, it can be observed directly in the vitreous ice layer using a cooled specimen holder on the microscope (in the second volume “Techniques”, Chapter 6, Section 2). If it is a bulk sample, it must be sliced. We can obtain thin slices directly by means of cryo-ultramicrotomy (“Techniques”, Chapter 4, Section 5). Otherwise the sample must be embedded in a low-temperature polymerizable resin in order to harden it. In this case, the sample must be dehydrated or desiccated beforehand. Dehydration occurs at low temperatures by substituting ice in a solvent; this is called cryo-substitution. Desiccation is carried out by means of sublimation (freeze drying). They will be followed both by infiltration and inclusion, also at low temperatures (see Prior Preparation in “Techniques”, Chapter 2, Section 10).

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.