I am purifying a small (14 kda) His-tagged protein that is very unstable, hydrophobic, positively charged, and very sensitive to degradation, oxidation, etc. It needs to be lyophilized (freeze-dried) for storage of longer than 1 week (which preserves its activity, based on other reports). Apparently quick freezing (dry ice / ethanol) with 10-50% glycerol, then storage at -80 C results in loss of activity.
However, I have no access to a freeze-drier. We do have a vaccuum pump and can make a cold trap (dry ice / ethanol), and have a speed vac. Is there any way to use some combination of this equipment to freeze dry? Would freezing my samples to, i.e., -80C and putting them directly in a speed vac (either room temperature, or in a cold room) likely work? Any other ideas? My sample volumes are 100ul to 500ul.
Thanks for any advice!