Structural evidence on DNA carcinogen interactions: N-acetoxy-N-2acetylaminofluorene binding to DNA

Artikel i vetenskaplig tidskrift, 1978

Linear dichroism (LD) gives useful information on the interaction between DNA and the directly acting carcinogen N-acetoxy-N-2-acetylaminofluorene (AAAF). In 50% methanol solvent with low ionic strength only a weak complex (van der Waals) appears. However, above 40° C strand separation takes place and a covalent aminofluorene complex forms. After renaturation a characteristic positive LD.band is observed at 306 nm. The average angular orientation of the longaxis of the fluorene moiety (47° to the local helix axis) is inconsistent with intercalation- It can be explained for instance by a free rotation around a C(DNA)-N (aminofluorene) bond or by a major groove site. The occupation density was 1–2 aminofluorene residues per 100 bases. With native DNA, AAAF slowly forms a covalent complex which has a negative LD at 307 nm. The orientation (70–90° ) is consistent with steric direction by the strand.