[Histonet] peroxidase/biotin block before or after permeabilization ?

[Yves Heremans]

Dear All,

I am performing peroxidase-DAB staining on cultured cells and was 
wondering whether peroxidase and biotin blocking should be performed 
before or after the permeabilization step with PBS + Tween ? Does 
permeabilization before blocking improve blocking due to better 
penetration ? My protocol is : peroxidase block with 0.3% H202 in 
methanol for 30 min. at RT, followed by avidin-biotin block from Dako, 
followed by PBS + Tween for 15 min. , followed by 30 min. block with 
fish skin gelatin in PBS.

Molly