Why does 5-methylchrysene interact with DNA as both a planar and a nonplanar polycyclic aromatic hydrocarbon? Quantum mechanical studies

Abstract

Polycyclic aromatic hydrocarbons are a large class of anthropogenic chemicals found in the environment. Some class members are potent animal carcinogens while other similar class members show little carcinogenic activity. When considering a series of in vitro studies of the interaction of polycyclic aromatic hydrocarbon bay region diol-epoxides with deoxyribonucleic acid (DNA), it was found that molecules with a crowded bay region behaved differently than molecules with a more open bay region. Molecules with a crowded bay region are nonplanar while in general polycyclic aromatic hydrocarbons are planar molecules. This dichotomy between planar and nonplanar subclasses proved useful, but when the experimental data was considered, 5-methylchrysene did not fit well into either class. In this study quantum mechanical calculations are reported that show 5-methyl chrysene and its diol-epoxides are nonplanar molecules, but the energy required to force them to be planar is considerably smaller than for most other nonplanar polycyclic aromatic hydrocarbons. The relationship to the experimental results that indicated 5-methylchrysene may behave like both a planar polycyclic aromatic hydrocarbon in some experiments and a nonplanar polycyclic aromatic hydrocarbon in others is discussed. © 2002 John Wiley & Sons, Inc. Int J Quantum Chem, 2002