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Destruction of microcystins (cyanotoxins) by UV-254 nm-based direct photolysis and advanced oxidation processes (AOPs): influence of variable amino acids on the degradation kinetics and reaction mechanisms.
Water Res. 2015 May 01; 74:227-38.WR

Abstract

Hepatotoxic microcystins (MCs) are the most frequently detected group of cyanobacterial toxins. This study investigated the degradation of common MC variants in water, MC-LR, MC-RR, MC-YR and MC-LA, by UV-254 nm-based processes, UV only, UV/H2O2, UV/S2O8(2-) and UV/HSO5(-). Limited direct photolysis of MCs was observed, while the addition of an oxidant significantly improved the degradation efficiency with an order of UV/S2O8(2-) > UV/HSO5(-) > UV/H2O2 at the same initial molar concentration of the oxidant. The removal of MC-LR by UV/H2O2 appeared to be faster than another cyanotoxin, cylindrospermopsin, at either the same initial molar concentration or the same initial organic carbon concentration of the toxin. It suggested a faster reaction of MC-LR with hydroxyl radical, which was further supported by the determined second-order rate constant of MCs with hydroxyl radical. Both isomerization and photohydration byproducts were observed in UV only process for all four MCs; while in UV/H2O2, hydroxylation and diene-Adda double bond cleavage byproducts were detected. The presence of a tyrosine in the structure of MC-YR significantly promoted the formation of monohydroxylation byproduct m/z 1061; while the presence of a second arginine in MC-RR led to the elimination of a guanidine group and the absence of double bond cleavage byproducts. It was therefore demonstrated in this study that the variable amino acids in the structure of MCs influenced not only the degradation kinetics but also the preferable reaction mechanisms.

Authors+Show Affiliations

Environmental Engineering and Science Program, University of Cincinnati, Cincinnati, OH 45221-0012, United States; Nireas-International Water Research Centre, University of Cyprus, P.O. Box 20537, 1678 Nicosia, Cyprus.Office of Research and Development, U.S. Environmental Protection Agency, Cincinnati, OH 45268, United States.Institute of Advanced Materials, Physicochemical Processes, Nanotechnology and Microsystems, National Center for Scientific Research "Demokritos", Patriarchou Grigoriou & Neapoleos, 15310 Agia Paraskevi, Athens, Greece.Water Quality Department, Athens Water Supply and Sewerage Company (EYDAP SA), Oropou 156, 11146 Galatsi, Athens, Greece.Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199, United States.Environmental Engineering and Science Program, University of Cincinnati, Cincinnati, OH 45221-0012, United States; Nireas-International Water Research Centre, University of Cyprus, P.O. Box 20537, 1678 Nicosia, Cyprus. Electronic address: dionysios.d.dionysiou@uc.edu.

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

25744186

Citation

He, Xuexiang, et al. "Destruction of Microcystins (cyanotoxins) By UV-254 Nm-based Direct Photolysis and Advanced Oxidation Processes (AOPs): Influence of Variable Amino Acids On the Degradation Kinetics and Reaction Mechanisms." Water Research, vol. 74, 2015, pp. 227-38.
He X, de la Cruz AA, Hiskia A, et al. Destruction of microcystins (cyanotoxins) by UV-254 nm-based direct photolysis and advanced oxidation processes (AOPs): influence of variable amino acids on the degradation kinetics and reaction mechanisms. Water Res. 2015;74:227-38.
He, X., de la Cruz, A. A., Hiskia, A., Kaloudis, T., O'Shea, K., & Dionysiou, D. D. (2015). Destruction of microcystins (cyanotoxins) by UV-254 nm-based direct photolysis and advanced oxidation processes (AOPs): influence of variable amino acids on the degradation kinetics and reaction mechanisms. Water Research, 74, 227-38. https://doi.org/10.1016/j.watres.2015.02.011
He X, et al. Destruction of Microcystins (cyanotoxins) By UV-254 Nm-based Direct Photolysis and Advanced Oxidation Processes (AOPs): Influence of Variable Amino Acids On the Degradation Kinetics and Reaction Mechanisms. Water Res. 2015 May 1;74:227-38. PubMed PMID: 25744186.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Destruction of microcystins (cyanotoxins) by UV-254 nm-based direct photolysis and advanced oxidation processes (AOPs): influence of variable amino acids on the degradation kinetics and reaction mechanisms. AU - He,Xuexiang, AU - de la Cruz,Armah A, AU - Hiskia,Anastasia, AU - Kaloudis,Triantafyllos, AU - O'Shea,Kevin, AU - Dionysiou,Dionysios D, Y1 - 2015/02/17/ PY - 2014/09/18/received PY - 2015/02/04/revised PY - 2015/02/06/accepted PY - 2015/3/7/entrez PY - 2015/3/7/pubmed PY - 2015/12/24/medline KW - Hydrogen peroxide KW - Mechanism KW - Microcystins KW - Second-order rate constant KW - UV-254 nm KW - Variable amino acids SP - 227 EP - 38 JF - Water research JO - Water Res VL - 74 N2 - Hepatotoxic microcystins (MCs) are the most frequently detected group of cyanobacterial toxins. This study investigated the degradation of common MC variants in water, MC-LR, MC-RR, MC-YR and MC-LA, by UV-254 nm-based processes, UV only, UV/H2O2, UV/S2O8(2-) and UV/HSO5(-). Limited direct photolysis of MCs was observed, while the addition of an oxidant significantly improved the degradation efficiency with an order of UV/S2O8(2-) > UV/HSO5(-) > UV/H2O2 at the same initial molar concentration of the oxidant. The removal of MC-LR by UV/H2O2 appeared to be faster than another cyanotoxin, cylindrospermopsin, at either the same initial molar concentration or the same initial organic carbon concentration of the toxin. It suggested a faster reaction of MC-LR with hydroxyl radical, which was further supported by the determined second-order rate constant of MCs with hydroxyl radical. Both isomerization and photohydration byproducts were observed in UV only process for all four MCs; while in UV/H2O2, hydroxylation and diene-Adda double bond cleavage byproducts were detected. The presence of a tyrosine in the structure of MC-YR significantly promoted the formation of monohydroxylation byproduct m/z 1061; while the presence of a second arginine in MC-RR led to the elimination of a guanidine group and the absence of double bond cleavage byproducts. It was therefore demonstrated in this study that the variable amino acids in the structure of MCs influenced not only the degradation kinetics but also the preferable reaction mechanisms. SN - 1879-2448 UR - https://www.unboundmedicine.com/medline/citation/25744186/Destruction_of_microcystins__cyanotoxins__by_UV_254_nm_based_direct_photolysis_and_advanced_oxidation_processes__AOPs_:_influence_of_variable_amino_acids_on_the_degradation_kinetics_and_reaction_mechanisms_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0043-1354(15)00084-6 DB - PRIME DP - Unbound Medicine ER -