RNase Inhibitor from human placenta is a pure recombinant enzyme expressed in E. coli. Placental Ribonuclease Inhibitor inhibits RNase by binding it in a 1:1 ratio with an association constant greater than 10¹⁴. Protein specifically inhibits ribonucleases  A, B and C. It is not effective against RNase 1, RNase T1, S1 nuclease, RNase H or RNase from Aspergillus. It is widely used to prevent RNA degradation in many applications for example: RT-PCR, in vitro RNA synthesis, RNA labeling reactions. It is active over a broad pH range (pH 5-8).