Bonding of Butylparaben, Bis(2-ethylhexyl)-phthalate, and Perfluorooctanesulfonic Acid to DNA: Comparison with Benzo[a]pyrene Shows Low Probability for Strong Noncovalent DNA Intercalation

Parabens,
phthalates, and perfluorinated compounds are pollutant
compounds used in cosmetics, plastics, and fire-fighting foams. All
three compounds have been studied over several years for toxicity
mechanism; however, a clear view of their ability to bind to DNA has
not been supplied empirically. In this work, a simulation study is
done to reveal the interaction of three of these pollutants, bis­(2-ethylhexyl)-phthalate
(DEHP), butylparaben (BPRB), and the protonated form of perfluoro­octanesulfonic
acid (PFOS­(H)), with DNA. The results show that the DEHP, PFOS­(H),
and BPRB bind with a probability of 1/5 to DNA, with respective bonding
energies −23.96 kJ/mol (PFOS­(H)), −94.92 kJ/mol (BPRB),
and −216.52 kJ/mol (DEHP). The positive control, benzo­[a]­pyrene
diol epoxide (BAP), which is known for its notorious DNA intercalation,
binds at a rate of 3/5 simulations, with bonding energies of −6544.52,
−7034.66, and −7578.67 kJ/mol. The results are compared
to empirical studies and conclusively show that all these pollutants
can interfere with transcription and DNA related mechanisms by forming
noncovalent interactions with DNA. The results show also that these
pollutants are unlikely to undergo strong noncovalent intercalation
to DNA, such as BAP, and do not possess the frontier orbital profiles
to undergo adduct formation. After many years of research and several
unanswered questions on the action of these pollutants on DNA, a calculation
on their properties hence to the DNA confirms that there is a low
probability for these to undergo a strong intercalation with DNA.
Literature shows however that the pollutants are strongly interfering
with the protein machinery and receptors on the cell surface and are
therefore still priority pollutants for ecotoxicity research.