title: Oxidation of the cyanobacterial hepatotoxin microcystin-LR by chlorine dioxide: reaction kinetics, characterization, and toxicity of reaction products.
abstract: Cyanobacteria are known producers of cytotoxins, hepatotoxins, and neurotoxins. The main toxins are microcystins, cyclic heptapeptide hepatotoxins, produced by strains of several cyanobacterial genera frequently found in eutrophied freshwaters. Due to the acute and chronic toxicity of microcystins, successful removal of these toxins in drinking water treatment processes is of increasing concern. In the present work the kinetics of microcystin-LR (MC-LR) oxidation by chlorine dioxide (ClO2) was studied with UV-spectrometry and high performance liquid chromatography (HPLC). Characterization of reaction products was performed with mass spectrometric (MS) analysis, while the toxicity of reaction products was tested with a protein phosphatase inhibition assay (PPIA). The main reaction products formed, dihydroxy isomers of MC-LR as identified by MS, were nontoxic according to the PPIA. The overall rate constant k for the reaction between MC-LR and ClO2 at 293 K and pH 5.65 was modest, k = 1.24 M(-1) s(-1), suggesting that ClO2 is not a suitable oxidant for the degradation of microcystins in drinking water treatment processes.
authors.affiliation: Department of Biochemistry and Pharmacy, Abo Akademi University, 20521 Turku, Finland. tkull@abo.fi
authors.forename: Tomas P J
authors.initials: TP
authors.lastname: Kull
authors.forename: Peter H
authors.initials: PH
authors.lastname: Backlund
authors.forename: Krister M
authors.initials: KM
authors.lastname: Karlsson
authors.forename: Jussi A O
authors.initials: JA
authors.lastname: Meriluoto
mesh_terms: D017606:Chlorine Compounds / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D000458:Cyanobacteria / Q000737:chemistry*; D004791:Enzyme Inhibitors; D005068:Eutrophication; D007700:Kinetics; D008387:Marine Toxins; D013058:Mass Spectrometry; D052998:Microcystins; D010084:Oxidation-Reduction; D010087:Oxides / Q000737:chemistry*; D010456:Peptides, Cyclic / Q000737:chemistry*; D010744:Phosphoric Monoester Hydrolases / Q000037:antagonists & inhibitors; D014871:Water Microbiology; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D017606:Chlorine Compounds; D004791:Enzyme Inhibitors; D008387:Marine Toxins; D052998:Microcystins; D010087:Oxides; D010456:Peptides, Cyclic; D014874:Water Pollutants, Chemical; C025109:chlorine dioxide; D010744:Phosphoric Monoester Hydrolases; C057862:cyanoginosin LR