NZY Ribonuclease Inhibitor (no DTT) is a highly pure recombinant enzyme displaying improved resistance to oxidation, which allows it to be stable at DTT concentrations lower than 1 mM. This property makes this ribonuclease inhibitor ideal for reactions that do not tolerate higher levels of DTT (>1 mM) and were RNases (EC 3.1) contamination is a potential problem, such as in real-time RTPCR assays. NZY Ribonuclease Inhibitor (no DTT) inhibits the activity of the omnipresent RNases of the pancreatic type, such as RNase A, RNase B and RNase C, by binding them noncovalently in a 1:1 ratio. It is not active against RNase 1, RNase T1, RNase T2, S1 nuclease and RNase H. NZY Ribonuclease Inhibitor (no DTT) can be useful in the following applications: cDNA synthesis, RT-PCR, in vitro transcription, in vitroreplication, RNA labelling or RNA isolation and purification.