Protein precipitation and overdried proteins

[Tiffy]

Hello,

I have a question about protein precipitation. I precipitate my proteins with methanol and chloroform. The final step is that I wash my pellets with methanol (1ml)and centrifuge down. Because of the fragility of the pellet I put it in all in the speed vac and dry the pellet. What could happen with the proteins when I overdry the pellet. After drying I resuspend the pellet with 2x sample buffer. When I have loaded the protein on the SDS-PAGE I observed that in the bottom of the tube a residue is visible. Something viscous or the like. Is this the overdried pellet and the proof that not everything was properly resuspended?
Thanks for all comments.
Tiffy

[danfive]

In best case scenario the overdried pellet can still be resuspended by adding time, sonication, gentle grinding, or using a stronger resuspension buffer. Worst case scenario you'll lose the overdried proteins and they won't resuspend.

Sometimes you need to have complimentary protein extraction/isolation methods for proteins based on their chemical characteristics: hydrophobic/hydrophilic proteins, glycoproteins, large mass proteins, high abundance/low abundance etc.

There isn't a perfect method for isolating 100% of proteins, you have to tailor your extraction/isolation to suit your target proteins.