The effects on biological materials of freezing and drying by vacuum sublimation. I. Development and testing of apparatus.

A vacuum sublimation apparatus is described which will permit, (a) the removal of water from virus suspensions at temperatures ranging down to -80 degrees C., (b) continuous operation with a minimum of attention from the investigator, (c) sealing off of samples at operating pressures (10(-5) mm. Hg), (d) simultaneous lyophilization of aliquot samples at different temperatures, (e) isolation of a portion of the apparatus without disturbing the remainder of the system, and (f) determination of the end-point of sublimation without disturbing the samples. The time required for drying 0.1 ml. of influenza virus suspension was shown to increase markedly with decrease of temperature, 8 days being required for dehydration at -80 degrees C. in contrast to 2 days at -30 degrees C. and 1 day at 0 degrees C.