DDX1 directly interacts with Nullbasic in vitro . The Octet Red system was used to measure binding events between Nullbasic and DDX1. A. BLI sensograms. Biotinylated recombinant Nullbasic-FLAG-V5-6 × His was bound to a streptavidin biosensor and applied to solutions containing 3.3 nM (green), 10 nM (light blue), 30 nM (red) or 90 nM (dark blue) of human recombinant Myc-DDK-tagged DDX1. B. The probe was also exposed to DDX5 solutions of the same concentration or with BSA at 90 nM as negative controls. The BLI experiment was repeated 3 times with similar results and a representative sensogram is shown.