Spectroscopic Analysis of the Binding of Paraquat and Diquat Herbicides to Biosubstrates

Francesca Macii, Rebecca Detti, Francesca Rita Bloise, Stefania Giannarelli and Tarita Biver
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Francesca Macii: Department of Chemistry and Industrial Chemistry, University of Pisa, 56124 Pisa, Italy
Rebecca Detti: Department of Chemistry and Industrial Chemistry, University of Pisa, 56124 Pisa, Italy
Francesca Rita Bloise: Department of Chemistry and Industrial Chemistry, University of Pisa, 56124 Pisa, Italy
Stefania Giannarelli: Department of Chemistry and Industrial Chemistry, University of Pisa, 56124 Pisa, Italy
Tarita Biver: Department of Chemistry and Industrial Chemistry, University of Pisa, 56124 Pisa, Italy

IJERPH, 2021, vol. 18, issue 5, 1-16

Abstract: The study of the interaction of persistent organic pollutants with biosubstrates helps to unravel the pathways for toxicity, however, few mechanistic data are present in the literature for these systems. We analyzed the binding of paraquat (PQ) and diquat (DQ) herbicides to natural calf thymus DNA and a DNA G-quadruplex by spectrophotometric titrations, ethidium bromide exchange tests, viscometry, and melting experiments. The interaction with bovine serum albumin (BSA) protein was studied spectrofluorimetrically at different temperatures. The retention of the targets on positive, negative, and neutral micellar aggregates and liposomes was analyzed by ultrafiltration experiments. Despite some favorable features, PQ and DQ only externally bind natural DNA and do not interact with DNA oligonucleotides. Both herbicides bind bovine serum albumin (BSA). PQ binds BSA mainly according to an electrostatics-driven process. However, ultrafiltration data also show that some hydrophobic contribution participates in the features of these systems. The practical problems related to unfavorable spectroscopic signals and inner filter effects are also discussed. Overall, both herbicides show a low affinity for nucleic acids and weak penetration into liposomes; in addition, the equilibrium constants values found for BSA system suggest optimal conditions for transport in the body.

Keywords: intercalation; external binding; transport; inner filter effect; micelles; liposomes; hydrophobicity; enthalpy-entropy compensation (search for similar items in EconPapers)
JEL-codes: I I1 I3 Q Q5 (search for similar items in EconPapers)
Date: 2021
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