Analysis protein expression - (Sep/29/2008 )

Hi everybody,
Does anyone knows if is necessary to sonicate cell pellets to analyse protein overexpression? I already found different protocols but I don’t know if treat cells only with loading buffer for electrophoresis will be enough release protein from cells.
Thanks

Usually you can boil samples in SDS loading buffer and get most of the proteins released from cells. I know that this works for yeast, bacteria, etc., not sure about mammalian cell lines as I don't work with that although I would suspect that it can be done. Sonicating is especially helpful if you want to determine whether your protein is soluble or present in inclusion bodies (for bacteria) or if you plan to do something else with it (say IP). If you are planning to do a western then it may not matter which method you choose, but if you aren't (you just want to visualize all proteins by coomassie) then you might be better off doing the sonication as it will separate out a lot of the junk.