I guess the first question is what system are you working in? PCNA is a good vital standard. Actin will also work. It really depends on what system you are working in mammalian, xenopus, yeast, etc... Guy Oshiro EMAIL: Oshiro_G at defiance.hsc.colorado.edu /\ /\ /\ / \/ \/\/ \ Science in the Rockies. / \ \/ \