How to make stable ATP solutions

[mansipan]

I have to use ATP solution daily and with time there is an increase in Pi in the solution, as observed by Malachite Green Reagent addition. Currently I am making 1 mM solution of ATP in 50 mM Tris HCl buffer pH 8.0 containing 50 mM NaCl and 5 mM MgSO4 and storing at 4 degree.

[CharonY]

ATP is extremely stable at the given pH and the most likely source for degradation is biological contamination. At -20 even with freeze-thaw cycles the lifetime is measured in years.

I presume that the salts in the buffer serve some function for other assays (typically NaCl is added for osmotic stability, which does not makes sense here and Mg is often just a co-factor. It does influence free energy of ATP hydrolysis though)? In most cases ATP is just titrated to neutral or slightly basic pH.

Your best bet is likely to aliquot the solution and freeze them at -20C.

[mansipan]

I have made fresh ATP solution and stored at -20 C but still there is some colour with Malachite green, it may be that there is some phosphate in the powder itself? Thanks for replying

[CharonY]

During synthesis there is a good chance (I am not sure how sensitive the assay is). Assuming that you tested the solution just after making it, it does indeed indicate presence of Pi rather than degradation. As long as the rate does not increase you should be fine.