Addition of 40 U of Murine RNase Inhibitor (NEB #M0314) or human placenta RNase Inhibitor (NEB #M0307) at room temperature effectively inhibits RNase 4 after standard digest conditions. For downstream applications that are not sensitive to detergents or chelating agents, a solution of 0.2 % (w/v) SDS and 20 mM EDTA pH 8.0 completely inactivates RNase 4.