by Patrick Frederix, of cryoWrite
The structure of proteins is of fundamental interest to understand their function and plays an important role in drug design. One of the techniques to determine the protein structure is cryogenic electron microscopy (cryo-EM). Hardware and software developments over the last decade have made cryo-EM the method of choice for protein structure determination. CryoWrite provides an automated sample preparation tool that addresses one of the bottlenecks in electron microscopy.
For cryo-EM, proteins are deposited on thin copper grids, that are then rapidly frozen. This freezing, also called vitrification, has to be very fast to prevent formation of ice crystals. This is obtained by working with very thin layers (<1µm) of sample and plunging of the grids into liquid ethane. To prevent rapid evaporation of the thin film, cryoWrite uses a cold-writing protocol, in which the temperature of grid, liquid and handling tweezers are precisely controlled at a defined temperature close to the water dew point. For fast freezing, liquid ethane is kept in a small container of liquid nitrogen that is at -196°C, but needs to be heated up in a controlled manner just above its melting point of -183°C.
For accurate temperature control during cold-writing and subsequent freezing, cryoWrite sets on TEC Controllers by Meerstetter Engineering. The accuracy, flexibility and integration capability of the TEC Controllers by Meerstetter are superior in the field. They work both with Peltier cooling systems to cool down to the dew point, but also with heater resistances for the ethane bath. For the temperature control of the ethane bath extra security features like run-away detection are essential security features of the system, to prevent evaporation of the combustible ethane. The temperature control that Meerstetter offers in the cryoWriter is therefore playing a crucial role in protein structure determination by our customers and safety in their laboratories.