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Which BSA do I order? - Enzymatic Assay Buffer (Aug/20/2008 )


I am hoping to screen some compounds for activity against casein kinase.
According to a product datasheet for Casein kinase (Millipore) - assays should be conducted in a buffer containing BSA. For starters, I don't really understand the reason for using BSA in this assay buffer, but my other problem is deciding which of the 3 million types of BSA to order for the buffer!

Can someone help me, at least to understand what the different preparations of BSA are suitable for?

Thankyou in advance


Albumin is the ubiquitous transport protein. I think you are using it in your assay to buffer proteins that inhibit kinase activity.

In some assays the albumin is used to sequester proteins prior to a centrifuge step which pulls down the albumin-protein complex. I think kinase doesn't bind albumin as well as others so remains in the supernatant which you presumably draw off and assay.

As to which preparation to use, check with the manufacturer. You probably want dry powder (use 10mg/ml?) and if you need a salt prep go for one made up in the same salt as you use in your buffer. If you go for a solution, go for one at the same pH as your assay conditions. Or at least choose the pH which will best buffer the expected change in pH. Check the literature, research papers will state the source and ofetn the catalogue number of the preparation used.


Call Millipore and ask their technical assistance. I'm sure they'll even be able to recommend a specific BSA that they sell.


we like to use delipidated fraction V bsa.

bsa is sometimes used to maintain a high protein concentration in an assay where the enzyme is not stable in low protein concentrations.