Electron-beam-induced amorphization of ice III or IX obtained by high-pressure freezing

Cryo-electron microscopy of vitrified specimens makes it possible to observe fully hydrated biological samples unimpaired by chemical fixation, staining and dehydration. High-pressure freezing represents important progress since it allows a 10-fold increase in the vitrification depth. High-pressure freezing can also induce the formation of undesirable high-pressure forms of ice. We show that ice III or IX is amorphized under the electron beam at a dose of about 2400 electronsnm⁻² and that the resulting amorphous ice is similar to the vitreous water obtained by high-pressure freezing.