the best way to remove protein from blood samples in order to purify RNA (including mIR) is to treat with proteinase K @ 55C for 10 to 30 min before commencing column purification. I can send you details if you wish
Laurence thanks for rapid reply, unfortunatedly proteinase K is out of the game for my purpose, I would need something for protein precipitation ( considering (NH4)2SO4, SDS, or TCA)