Non-covalent DNA-binding has been studied of 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (Me-IQ) and 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (Me-IQx), strong mutagens found in broiled foods. These mutagens are intercalated into DNA, as found by ultraviolet absorption gel electrophoresis. The binding of IQ is stronger with GC pairs than AT pairs in DNA. The binding constants with calf thymus DNA are 1.6 × 106 (Me-IQ), 0.9 × 106 (IQ) and 0.7 × 106 M−1 (Me-IQx) at pH 6.0. This order of DNA affinity agrees with the order of mutagenicity towards Salmonella typhimurium TA98.
