Western blot using anti-ATR antibody shows detection of ATR in HeLa cell nuclear extract (lane 1). Lane 2 shows negligible staining after pre-incubation of antibody with the immunizing peptide (50 ?g peptide for 1 h at room temperature followed by centrifugation). A 4-8% gradient gel was used for separation. Goat serum was used at 5% for blocking. The arrowhead corresponds to 301 kDa ATR when compared to MW markers (Lane M). The primary antibody was used at a 1:1, 400 dilution.