I think by using TCA

TCA

Dear Safa..

We are following this protocol in our lab..

The serum must be separated from the whole blood and about 900 µL of serum has to incubated with 100 µL of the intended radio-complex at 37 ºC up to 1 hour. 1mL of 10% TCA add to the complex and the centrifuge mixture at 2000 rpm for 5 minutes. Supernatant collect in a different tube, marked as S-1 and the pellet resuspend in 1mL of 5% TCA and centrifuge again at 2000 rpm for 5 minutes The supernatant collect in separate tube and marked as S-2. Radioactivity measured in both the precipitate and supernatant fraction (S-1+S-2) in a well type NaI based gamma spectrometer. Protein binding of the radio-complex can be express as a percent fraction of radioactivity bound to protein to that of the total radioactivity. The following formula use for the calculation of percentage protein binding

Protein Binding (%) = Counts in pellet/Total counts (Pellet+S-1+S-2) × 100.

Thanks..

Thanks very much for your answers