I need to measure plasma membrane ATPase and would like a detailed protocol of how to prepare ATP to be added as a substrate. I have read that some researchers do it in dowex 50W, but I am not sure how this is done.
I think by BTP you mean the buffer Bis-Tris-propane. It seems to me that you can prepare the buffer and the ATP separately. You can dissolve disodium ATP in water at 100 mM and adjust the pH to 7.0 with sodium hydroxide. The ATP stock solution can be stored at -80oC indefinitely. This solution can be added to the assay buffer to the desired concentration.