24bp HPLC-grade RNA oligonucleotide 5´-GCGUCGUACGCUAG CGUACGACGC-3´ was purchased from Integrated DNA Technologies. Sample preparation was performed as previously described . Samples were subjected to 4% native PAGE and stained with gel-red (Biotium). For AFM, we followed previously described protocol with modification. Briefly, we mixed 10 ng HMW Poly(I:C) and 5 ng purified MDA5 protein in 10 μl of buffer and then incubated in the presence or absence of 10 ng DHX29 in buffer A (pH 7.4, 50 mM NaH2PO4, 50 mM glycine, 14 mM succinic acid, 10 mM MgCl2, 10 μM ZnCl2, 5 mM DTT and 2.5 mM ATP) for 40 min on ice. The mixtures were dropped onto the flat mica plate (molecular level) for 10 min and then washed 5 times with PBS to remove excess salt. AFM imaging and analysis were carried out using the Bruker MultiMode AFM with scanasyst, PeakForce QNM imaging modes, Peak Force Tapping technology, and NanoScope Analysis software.