title: Solubilization of 6-oxybenzo(a)pyrene radical by caffeine and DNA as studied by magnetic resonance. Observation of intermolecular charge transfer.
abstract: Crystals of 6-oxybenzo(a)pyrene free radical, formed chemically from the hydroxy derivative of the carcinogen benzo(a)pyrene, can be solubilized in aqueous solutions of DNA and of caffeine. ESR spectral evidence indicate that the radicals exist as dispersed monomers associated with DNA and with caffeine. Comparison of NMR spin-lattice and spin-spin relaxation times in the protons of caffeine has given direct evidence that a part of the unpaired electron (at least 10(-4)) is transferred from the radical to the associated caffeine molecule. Simple consideration of Mulliken's charge transfer theory, however, leads to the conclusion that the intermolecular charge transfer is not likely to be a major source of stabilization energy of the complex.
mesh_terms: D001580:Benzopyrenes; D002110:Caffeine; D004247:DNA; D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals; D009682:Magnetic Resonance Spectroscopy; D012995:Solubility; D013696:Temperature
chemical_list: D001580:Benzopyrenes; D005609:Free Radicals; D002110:Caffeine; D004247:DNA