<b>The Cas9 polyclonal antibody recognizes wild-type and nickase mutant Cas9 protein.</b> HEK 293 cells were transfected with plasmids encoding either wild-type or mutant Cas9 transcripts expressed from the CMV promoter using Xfect Single Shots; untransfected cells were used as a negative control. After 48 hr, the cells were lysed and Western blotting was performed with 3.5x10⁴ cells for the negative control and 0.7 x 10⁴ cells for Cas9-expressing cells. Blots were probed with primary anti-Cas9 polyclonal antibody (1:5,000 dilution). For detection, an HRP-conjugated goat anti-rabbit secondary antibody was used (1:5,000 dilution), and signal was detected using ECL reagent. The image shown is a 0.5 sec exposure.