Can we use indifferently skim milk or BSA to block membranes before using anti-phospho antibodies for Western Blot.

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Hi,

Both usually used.In my experience, skim milk the best.

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Because all antibodies are different and you can't necessarily say that one condition is best for all blots, but generally for anti-phospho antibodies you don't want to use milk. Milk contains lots of phospho-proteins (especially if you are looking for a Tyr-P) which can interfer with your specific signal. BSA is usually a better choice but as I said, all antibodies are different. I have seen a phospho-antibody which was cleaner with milk. Additionally these antibodies can be fussy about nitrocellulose versus PVDF. You may find that you need to test multiple conditions before determining what is best with your specific antibody and experiemental conditions.

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we use a commercial, non-protein based blocking solution; milk contains a relative high amount of phosphoproteins and may disturb IB with antiphosphoprotein; anyway, one has to test various blocking solutions for optimum performance...

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In case of phoshoproteins study milk isnot recommened as a blocking as milk contains casein which is a phosphoprotein and it will cause a very high background as the phospho-antibody detect it in the milk so its better to use 3%BSA in 1X TBST as blocking buffer and base for diluting first and second antibodies

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