I do western blotting with these lysates and i just want to minimize the degradation of protein as much as possible and i also want to know whether the storing temperature (-20 or -80) have any effect on the protein integrity.
I would like to add that protein lysates from cells after boiling with Laemmli's sample buffer can be stored safely at either -20 or -80 degree C. The boiling inactivates proteases that degrade proteins. However, certain chromatin binding proteins may require proper processing of the frozen protein samples (a quick thawing of samples at 37 degree C, vortexing, heating, vortexing, and centrifugation) before analyzing by immunoblotting.
That all depends on the frequence you use. If u use it very often, it is better for you to store you lysates in -20, since it will not take so long time to dissolve the lysates. Besides, the repeated freezing and thawing is not good for the protein integrity. U can chose -80 for storing, if u just use it once or twice a month.
I would like to add that protein lysates from cells after boiling with Laemmli's sample buffer can be stored safely at either -20 or -80 degree C. The boiling inactivates proteases that degrade proteins. However, certain chromatin binding proteins may require proper processing of the frozen protein samples (a quick thawing of samples at 37 degree C, vortexing, heating, vortexing, and centrifugation) before analyzing by immunoblotting.
I advise you to store the protein extraction in sample buffer as aliquots at -80ºC for minimize the action of proteases although your buffer have proteases inhibitors.
Boil it in Laemmli buffer, aliquote them and store at -80C. This way you can minimize or prevent degradation. Make enough number of aliquotes in case you are storing without boiling. Repeated thawing can excessively degrade the proteins.