Arsenic and hydrogen peroxide treatments result in oxidation of Sp1 protein. Immunoprecipitated (IP) Sp1 from control, arsenic, or hydrogen peroxide-treated samples was incubated with BIAM, and this was followed by detection by immunoblotting (IB) with streptavidin-conjugated HRP. The same immunoprecipitate was subjected to detection by Sp1 antibody as a loading control. BIAM/Sp1 signal ratios represent relative BIAM incorporation.