NZY Ribonuclease Inhibitor is a recombinant protein purified from Escherichia coli. It inhibits the activity of ribonucleases (RNases; EC 3.1) of the pancreatic type, such as RNase A, RNase B and RNase C, by binding them noncovalently in a 1:1 ratio. NZY Ribonuclease Inhibitor is useful in any application where RNase contamination is a potential problem. For instance, it can be used to protect template RNA in cDNA synthesis reactions, RT-PCR or in vitrotranscription/translation, as well as to protect viral RNA during in vitro replication. In addition, it will inhibit RNases during RNA isolation and purification and during RNase-free antibodies preparation. NZY Ribonuclease Inhibitor is not active against RNase 1, RNase T1, RNase T2, S1 nuclease and RNase H.