Two nitro derivatives of azabenzo[a]pyrene N-oxide: Electronic properties and their relation to mutagenic activity

• Published in: Journal of hazardous materials Vol. 285; pp. 94 - 102
• Main Authors: Ostojic, Bojana D, orevic, Dragana S
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 21.03.2015
• Subjects: 1-Nitro-6-azabenzo[a]pyrene; 3-Nitro-6-azabenzo[a]pyrene; Activation; Benzopyrenes - chemistry; Benzopyrenes - toxicity; Charge distribution; Cyclic N-Oxides - chemistry; Cyclic N-Oxides - toxicity; Derivatives; DFT calculations; Dipole moment; Electron affinity; Electronics; Electrostatics; Environmental pollutants; Enzymes; Isomers; Mutagenic activity; Mutagens - chemistry; Mutagens - toxicity; Salmonella typhimurium; Salmonella typhimurium - drug effects; Salmonella typhimurium - genetics; 1-Nitro-6-azabenzo[a]pyrene; 3-Nitro-6-azabenzo[a]pyrene; Environmental pollutants; Mutagenic activity; DFT calculations
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2014.11.032

•Molecular properties of nitro isomers of azabenzo[a]pyrene N-oxide are investigated.•Stability, ionization potential, electron affinity, and polarizability are determined.•High quality DFT methods are employed.•Nitroreduction, oxidation, and polarizability are not crucial for mutagenicity.•Dipole moment and electronic charge distribution are important for characterization. The equilibrium geometries, relative energies, IR and Raman spectra, vertical ionization potentials (IP), vertical electron affinities (EA), dipole moments (μ), electronic dipole polarizabilities (α), and molecular electrostatic potentials (MEP) of two species that show very high mutagenicity, 1-nitro-6-azabenzo[a]pyrene N-oxide (1-N-6-ABPO) and 3-nitro-6-azabenzo[a]pyrene N-oxide (3-N-6-ABPO), are investigated by means of Density Functional Theory (DFT) using B3LYP functional with different basis sets. The 3-N-6-ABPO isomer was estimated to be much more mutagenic in Salmonella typhimurium tester strain TA98 (396 000 revertants/nmol) than 1-N-6-ABPO (36100 revertants/nmol) (Fukuhara et al., 1992). The results show that for both isomers the structural, energetic, and vibrational properties are similar. The orientation of the nitro group with respect to the plane of the aromatic system as well as the nitroreduction and oxidation reaction and polarizability seem not be important for the determination of different mutagenic behavior of these isomers. However, the dipole moment of 3-N-6-ABPO is about 3 times that of 1-N-6-ABPO. The larger dipole moment and the different electronic charge distribution of 3-N-6-ABPO compared to 1-N-6-ABPO imply stronger electrostatic and inductive molecular interactions so that the active site of the enzyme involved in the mutagenic activation can more effectively bind 3-N-6-ABPO compared to 1-N-6-ABPO.