Fig. 4. Dose dependency of the effect of hemin on the capability of oxidizing benzidine for the p53-expressing K562 clone A5 and the mock-transfected clone M1. Cells at an initial concentration of 0.2 x 106 cells/ml were incubated at 32°C (i.e., the temperature permissive for the wild-type conformation of p53) with or without hemin at different concentrations. After 4 days, cells were subjected to a benzidine oxidation test. The fraction (A) or total number per ml (B) of benzidine-oxidizing cells are shown. Mean values from three to nine separate experiments are shown. •, ptsp53/A5; {square}, Mock 1.