Protein precipitation. Overdrying proteins - (Apr/25/2008 )

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). 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 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

-Tiffy-

QUOTE (Tiffy @ Apr 25 2008, 12:26 AM)

it is not recommended to dry protein pellets totally as re-solubility even in SDS_PAGE sample buffer is decreased; total drying may favour hard-soluble aggregations; if you used total lysate and did not treat with DNAse you may observed traces of DNA, or lipids

-The Bearer-

But how can I remove methanol without destroying my fragile pellet? The proteins stem from a nucleus fraction. I want to load 50µg protein. But to load this amount I have to pipette about 70µl volume. I am little bit helpless.
Any suggestions?
Thanks
Tiffy

-Tiffy-

QUOTE (Tiffy @ Apr 25 2008, 03:52 AM)

for a reagent cup, after centrifugation, pour away methanol and let it dry by air for half an hour, the opening upside down; some minor traces of methanol may be left but this does not matter; then boil it in SDS sample buffer

-The Bearer-