Figure 1. Treatment of HeLa cells with UV stimulates phosphorylation of Chk1 at Ser317, detected by the PathScan® Phospho-Chk1 (Ser317) Sandwich ELISA Kit #7870, but does not affect the levels of total Chk1 detected by PathScan® Total Chk1 Sandwich ELISA Kit #7872. HeLa cells (80-90% confluent) were treated with 100 mJ/cm2 UV with 1 hour recovery at 37ºC. The absorbance readings at 450 nm are shown in the top figure, while the corresponding Western blots using Chk1 Antibody #2345 (left panel) or Phospho-Chk1 (Ser317) Antibody #2344 (right panel) are shown in the bottom figure.