Abstract
Experimental evidence has been obtained for the involvement of charge transfer in the interaction between DNA and 4-nitroquinoline 1-oxide and related carcinogens. Examinations were made on the nature of hypochromic changes exhibited in the absorption spectra of DNA and deoxyribonucleosides by the presence of the following compounds: Quinoline 1-oxide, 4-nitroquinoline, 4-nitroquinoline 1-oxide, 4-nitroquinaldine 1-oxide, 6-chloro-4-nitroquinoline 1-oxide, 4-hydroxyaminoquinoline 1-oxide, and 4-nitropyridine 1-oxide. The spectral changes were characterized by two common features: (1) Hypochromic changes were produced in the shorter wavelength regions of spectra of DNA and deoxyribonucleosides, the greater part of longer wavelength side slopes of the original spectra remaining unaffected, and (2) in every case of mixed systems of carcinogenic quinoline derivatives, larger changes were produced with purine deoxyribonucleosides than with pyrimidine deoxyribonucleosides. The degree of hypochromicity was expressed in terms of percentage hypochromicity, and it was revealed that there exists a close correlation between degree of hypochromic effect and biological activities of the compounds examined. It was found that the percentage hypochromicity values of quinoline derivatives run parallel with the half-wave potentials reported by Kawazoe et al., and with the quantities of charge transfer computed by Nagata et al.
