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protein precipitation during gel loading - (Feb/13/2006 )

hello all
a little problem during western blot. i prepared samples (they are in 1%SDS-H20) i add laemmli buffer (containing the mercaptoethanol)...i boiled them and during the loading into the stacking gel i noticed the samples were semi-solid! it was very hard to load them and they looked horrible! after a 1/2 an hour, the run looks ok. can anybody explain what happened there?


Genomic DNA present in the prep can make them that way. If you sonicate rather than lyse the cells it goes away.


a too low laemmli concentration may affect that.
I've got that pb, and solve it by 2ways : carefully add the lammli 5x in each tube to be sure getting the right volume of it (sticks to the tip frequently and you don't have the 2µl in 10µl final for ex)
Complete with laemmli 1X instead of ddH2O.

I also clean by distilled water the well.


thank you for the replies.
i hope i still could get the western blot developed ok. this was tissue extracted with trizol so i am sure i carried over some genomic DNA contamination.
regarding the laemmli buffer, i always use 6ul in 30ul final volume (5x)/well so i thought it was enough.
is there a way to avoid this problem? i am just concerned that i was not able to load uniformly the samples. some sample was floating around after i loaded it. of course i'll develop for the actin but i would like to set up a good protocol for next time. maybe there's a good solvent in which i could redissolve the protein pellet after isolation (now i am using 1%SDS-H20 as suggested by the manufacturer).