Interaction of polynuclear aromatic hydrocarbons, 4‐nitroquinoline 1‐oxides, and various dyes with DNA

Abstract By using the flow dichroism method, in vitro interaction of the aromatic polynuclear hydrocarbons with calf thymus DNA was studied. A clear dichroism of the hydrocarbons which interacted with DNA was observed, showing a specific type of interaction. Hydrocarbons were classified into two groups, depending on whether the orientation is parallel or perpendicular to the direction of flow. 3,4‐Benzopyrene, pyrene, and phenanthrene belong to the first group, and the second group contains 20‐methylcholanthrene, tetracene, pentacene, and coronene. 4‐Nitroquinoline 1‐oxide (4‐NQO) and its derivatives have also been found to be oriented parallel to the planes of bases of DNA, and a distinct parallel was found between the amount of binding and carcinogenicity. Base specificity of binding of 4‐NQO with DNA‐was studied, and purines were suggested to be active sites of interaction. Actinomycin D, several acridine dyes, and methylene blue etc. were found to be oriented parallel to the planes of DNA bases, and in the cases of acridine dyes this finding does not contradict the intercalation mechanism proposed by Lerman.