Helmut Formanek

The interpretation of radiation damage measurements with electron diffraction of organic materials at very low temperatures

Abstract At very low object temperatures organic specimens suffer not only radiation damage but, to a higher extent, charging and heating during electron irradiation due to very low electrical and thermal conductivities of organic materials. The fading of electron diffraction patterns is seriously influenced by the superposition of both effects. For this reason an exact determination of the progress in radiation damage is nearly impossible by direct observations of the diffraction patterns, particularly for obtaining the cryoprotection factors of organics. Charging and subsequently heating cause intrinsic motions of the irradiated areas which also seem to lead to a destruction of the crystallinity. With a suitable preparation of organic specimens, charging and heating effects at very low temperatures could be avoided, and it could be demonstrated that the true cryoprotection was relatively good.

High resolution cryo electron microscopy of specifically stained specimens

Abstract At very low temperatures organic specimens with attached metal atoms can be irradiated with a relatively high electron fluence without losing the characteristic features of their architecture. This is demonstrated on three examples: a metal-organic molecule, a membrane-like biological layer, and a three-dimensional polymeric copper complex.