A 10.0-gsample of protein was hydrolyzed. A 3.0-mg portion of 14C-labeled threonine, with specific activity of 1000 cpm/mg, was added to the hydrolysate. After mixing, 11.5 mg of pure threonine was isolated and found to have a specific activity of 20 cpm/mg.
(a) What percentage of this protein is threonine?
(b) Had 11C (t1/2 = 20.3 min) been used instead of 14C, how would the answer change?
Assume all numerical values are the same as in part (a) and that the elapsed time between' the two specific activity measurements was 32 min.