A 16 hour incubation is performed with ΦX174 DNA- HaeIII Digest (NEB# N3026). This assay checks for endonuclease, exonuclease and binding protein contamination. A 4 hour incubation is performed with ΦX174 RFI DNA (NEB# N3021). This is a sensitive assay for nonspecific endonuclease. A 1 hour incubation with a RNA ladder is performed. This assay checks for RNAse.