Radioactive Assay
 

So i have a radioactive complemenation assay PTS sugar -Mannitol using a scintillation counter. I am assuming that its 100% efficient therefore cpm= dpm.
The control value was 500 cpm Sugar-P
10 ul of the HPr protein was 3000 cpm Sugar -P
I subtracted these two values to correct for background radiation. therefore the actual cpm of my sample was 2500 cpm and hence 2500 dpm. Here is where I am lost. I figure i need to find specific activity in (ci/mmol). since 1 dpm = 2.22 x10^22 ci .I converted my dpm and got that 2500 dpm = 1.12613E-09 Ci. Is this value my specific activity or is there something more i need to do with it?

Here is some background information: the stock concentration of the E.coli protein HPr sample is 4 ug ml-1. The total volume of the assay was 100 ul