The standard measure of the amount of radioactive decay is the Curie (Ci), which is defined as the quantity of radioactive material that gives 2.22 x [10.sup.12] disintegrations per minute (dpm).
Specific activity is usually reported as counts per minute (cpm), which is lower than disintegrations per minute because only a percentage of disintegrations are actually measured by analytical devices.
Means and standard errors of performance for total activity were 15.1 [+ or -] 1.4 disintegrations per minute
per milligram dry matter (dpm [mg.sup.-1] DM); for specific activity, they were 89.0 [+ or -] 8.1 disintegrations per minute
per milligram protein (dpm [mg.sup.-1] protein).
Where net dpm is the disintegrations per minutes
minus back ground counts, [V.sub.1] is the volume of assay system, [V.sub.2] is the amount loaded for counting, t is the reaction time and w is the weight of the sample.