The relative stability of a mercury stain at room temperature and liquid helium temperature

Abstract

Observations of the localization of the mercurial stain TAMM [tetrakis (acetoxymercuri) methane] have been made at room temperature and liquid helium temperature. Mercurial stains do not maintain a fixed position at room temperature in the electron microscope. In order to record room temperature micrographs with the minimum possible dose, a special single-electron-counting electron microscope system was used. Micrographs were taken at liquid helium temperature using a prototype microscope with a superconducting electron objective lens. Tropomyosin paracrystals were chosen as a convenient test object. At room temperature the fine banding pattern of the paracrystals was barely resolvable or not resolvable at all. At liquid helium temperature the fine banding pattern of the paracrystals was easily observed and more than one micrograph could be taken before the banding pattern faded. These observations indicate that this mercurial stain is more stable in position at liquid helium temperature than at room temperature.