rat plasma and kidney microsomes. At least 9 precipitate arcs were detected with preparations from livers of normal rats. Similar patterns were obtained with preparations from livers of rats which had been injected with 2-aminofluorene or 2-acetylaminofluorene 72 hr earlier. In the latter case, at least 2—3 arcs were shown to fix anti-2azofluorene-'251 antibody, indicating that some microsoma...

A synthetic DNA fragment was constructed to determine the effect of 5' and 3' neighbors of guanine runs on the binding of chemical carcinogens. Determinations were made on the relative intensity of reactivity between aflatoxin B1 or benzo(a)pyrene and methylnitrosourea or 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea with various guanine positions in an endlabeled DNA fragment of known sequence....