Jet freezing in enzyme and cosmetic research
Freezing has turned out to be the only method capable of immobilizing biological material in its natural state. Freeze-fracturing and replication complete this preparation protocol of specimens for transmission elctron microscopy (TEM) which is based on purely physical methods. With a propane-jet, specimens of a thickness up to 20 μm can be frozen without detectable ice crystal formation, Cell and macromolecule suspensions, emulsions, liquids and polymers in a solvent can be “sandwiched” between two copper foils and kept in place while a coolant is moved very rapidly against the opposite surfaces. In the present jet freezing device (JFD 030) the temperature of the specimen, while residing in a thermostatically controlled chamber, can be monitored between 10 and 90°C immediately prior to freezing. Thus physiologically interesting situations can be immobilized and any precooling of the specimen is avoided. A special device enables the abslutely simultaneous exposure of the specimen to the double-sided jet of the coolant. High cooling rates with an exceptional reproducibility are achieved routinely (Fig.1).