An experimental and theoretical study of Coprinus cinereus peroxidase-catalyzed biodegradation of isoelectronic to dioxin recalcitrants

Isoelectronic to dibenzo-p-dioxin (DBD) compounds (ID) containing nitrogen and/or sulfur atom instead of oxygen atom can be oxidized in the presence of fungal peroxidase. To elucidate the structure/activity relationship the redox potential of ID's was determined and correlated with calculated properties from ab initio calculations. The redox potential of ID's varied between 0.16 and 1.46 V versus standard calomel electrode (SCE) in acetonitrile. Spectral measurements and ab initio quantum chemical calculations showed that the redox potential correlated with the quantity of heteroatom conjugation with the 6π-aromatic system. The reactivity of ID's decreased if the redox potential of ID's increased. The calculations of docking and molecular dynamics revealed that all ID's may form the stable complexes in the active center of peroxidase. The acquired results permitted to conclude that low reactivity of ID's and their halogenated derivatives is associated with the high redox potential of recalcitrants.