Blocking in ChIP - (Sep/30/2005 )

Dear all:

My lab usually uses a Protein A/G 50% slurry, blocked with high quality BSA and salmon sperm, usually overnight at 4C. This is homemade, of course. When using them, we also do an overnight preclearing.

I noticed that other people use only an hour at 4C to block the beads, or to preclear. Has anyone tried to see if there is a difference?

Also, is there an expiration date for such beads? How do they compare to upstate's beads?

Thanks!

therotically blocking for a longer time is better. But my transcription factor tends to degrade even in presence of protease inhibitor. So overnight blocking is not suitable in this case.

can you send me the protocol for blocking the protein A/G agarose you use in your lab...thanks