Oxidation by-products formation of microcystin-LR exposed to UV/H2O2: Toward the generative mechanism and biological toxicity

Zong, Wansong; Sun, Feng; Sun, Xiaojing

doi:10.1016/j.watres.2013.03.037

Cited by 59 publications

(30 citation statements)

References 28 publications

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“…The proposed mechanism is in agreement with the review by Pantelic et al, where it is mentioned that the uracil group is the most susceptible to chemical oxidation (Pantelić et al, 2013). (Merel et al, 2010b;Zong et al, 2013). The hydroxylation on the conjugated double bonds leads to the formation of isomers.…”

Section: Transformation Products By Chlorinationsupporting

confidence: 90%

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Study of cyanotoxin degradation and evaluation of their transformation products in surface waters by LC-QTOF MS

et al. 2019

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In the present work, the degradation of three cyanotoxins from the hepatotoxins group was investigated under laboratory-controlled experiments in water samples. Surface waters spiked with microcystin-LR (MC-LR), nodularin (NOD) and cylindrospermopsin (CYN) were subjected to hydrolysis, chlorination and photo-degradation, under both sunlight (SL) and ultraviolet (UV) radiation. A total of 12 transformation products (TPs) were detected and tentatively identified by liquid chromatography coupled to quadrupole time-of-flight mass spectrometry (LC-QTOF MS). These comprised: 6 chlorination TPs (3 from CYN and 3 from MC-LR, 2 isomers); 4 UV TPs (all from CYN); and 2 sunlight TPs (one isomer from MC-LR and another from NOD). No TPs were observed under hydrolysis conditions. The chemical structures for all TPs were tentatively proposed based on the accurate-mass QTOF MS full-spectra. Analysis of real-world samples collected from the Peñol reservoir (Antioquia, Colombia) revealed the presence of MC-LR and CYN as well as a sunlight TP identified in the laboratory experiments. Data presented in this article will assist further research on TPs potentially formed in future tertiary degradation processes applied for the removal of organic micro-pollutants in water; as well as improving available knowledge on the toxic implications of cyanobacterial toxins TPs in surface waters.

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Section: Transformation Products By Chlorinationsupporting

confidence: 90%

“…Hydroxylation and chlorination have also been proposed for m /z 1047, 1063, 1097, 1115, 993 and 1011 by (Merel et al, 2009); and 795, 1029, 1047, 1081 and 1099 by (Zong et al, 2013).…”

Section: Several Tps Of Mcs Have Been Detected By Various Authors In mentioning

confidence: 99%

Study of cyanotoxin degradation and evaluation of their transformation products in surface waters by LC-QTOF MS

et al. 2019

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“…47 In addition, several previous studies have indicated that intermediate radicals could promote detoxification by oxidation of the diene bonds of the Adda moiety. 48,49 Effects of pH on MC-LR Decomposition and Detoxification. As shown in Figure 5, Total MC-LR concentration by chlorination alone was not altered substantially in the pHbuffered solutions for pH values of 6.5, 7.5, and 8.5, for chlorine:MC-LR molar ratios of 0:1−4:1.…”

Section: Environmental Science and Technologymentioning

confidence: 99%

Chlorine/UV Process for Decomposition and Detoxification of Microcystin-LR

Zhang

Yang

et al. 2016

Environ. Sci. Technol.

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Microcystin-LR (MC-LR) is a potent hepatotoxin that is often associated with blooms of cyanobacteria. Experiments were conducted to evaluate the efficiency of the chlorine/UV process for MC-LR decomposition and detoxification. Chlorinated MC-LR was observed to be more photoactive than MC-LR. LC/MS analyses confirmed that the arginine moiety represented an important reaction site within the MC-LR molecule for conditions of chlorination below the chlorine demand of the molecule. Prechlorination activated MC-LR toward UV254 exposure by increasing the product of the molar absorption coefficient and the quantum yield of chloro-MC-LR, relative to the unchlorinated molecule. This mechanism of decay is fundamentally different than the conventional view of chlorine/UV as an advanced oxidation process. A toxicity assay based on human liver cells indicated MC-LR degradation byproducts in the chlorine/UV process possessed less cytotoxicity than those that resulted from chlorination or UV254 irradiation applied separately. MC-LR decomposition and detoxification in this combined process were more effective at pH 8.5 than at pH 7.5 or 6.5. These results suggest that the chlorine/UV process could represent an effective strategy for control of microcystins and their associated toxicity in drinking water supplies.

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“…Accordingly, the specific generative mechanism of MC-GSHs was confirmed by comparing their secondary structures with MCLR and MCRR (with the assistance of Compass Isotope Pattern software). MS/MS analysis showed partial CID fragments of MCLR ( m/z 995.5558) were detected at m/z 213.0831, 286.1477, 553.3069, 682.3956, and 866.5147 (Figure 2(a)), corresponding to the secondary structures of [Glu-Mdha+H] + , [MeAsp-Arg+H] + , [Mdha-Ala-Leu-MeAsp-Arg+H] + , [Arg-Adda-Glu-Mdha+H] + , and [Mdha-Ala-Leu-MeAsp-Arg-Adda+H] + /[Arg-Adda-Glu-Mdha-Ala-Leu+H] + [22, 23]. For MCRR ( m / z 519.7903, z = 2), its primary CID fragments were detected at m/z 213.0831, 286.1477, 298.6720, 413.7556, 440.2252, 455.2741, 484.2768, and 599.3552 (Figure 2(b)), corresponding to the ions of [Glu-Mdha+H] + , [MeAsp-Arg+H] + , [Mdha-Ala-Arg-MeAsp-Arg+2H] 2+ , [Ala-Arg-MeAsp-Arg-Adda+2H] 2+ , [Mdha-Ala-Arg-MeAsp+H] + , [Arg-Adda-Glu-Mdha-Ala-Arg+2H] 2+ , [Arg-MeAsp-Arg-Adda-Glu-Mdha+2H] 2+ , and [Arg-Adda-Glu+H] + /[MeAsp-Arg-Adda+H] + .…”

Section: Resultsmentioning

confidence: 99%

Molecular Mechanism for the Regulation of Microcystin Toxicity to Protein Phosphatase 1 by Glutathione Conjugation Pathway

Zong

Wang

et al. 2017

BioMed Research International

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Glutathione (GSH) conjugation was an important pathway to regulate the toxicity of microcystins (MCs) targeted to protein phosphatases. To explore the specific molecular mechanism for GSH detoxification, two typical MC-GSHs (derived from MCLR and MCRR) were synthesized, prepared, and purified according to previous research. Then, the reduced inhibition effect for MC-GSHs on protein phosphatase 1 was verified by comparing with their original toxins. To further clarify the molecular mechanism for MC-GSHs detoxification, we evaluated the interactions between MCs/MC-GSHs and PP1 with the assistance of MOE molecule simulation. When GSH was introduced to MCs, the covalent binding (Mdha7 to Cys273), the hydrophobic interaction (Adda5 with PP1), the hydrogen bonds (especially for Lys2-Arg96 and Glu6-Tyr272), the covalent combination (between Mdha7 and Cys273), and the ion bonds (between Mn2+ and Asn124/His248/Asp64/His66) of MCLR/MCRR-PP1 complexes weakened to a certain extent, while the ion bonds between Mn2+ and His173/Asp92 residues increased. It was not difficult to find that the toxicity of MCs was closely related to the above sites/interactions and the above key information for MCs-PP1; MC-GSHs-PP1 complexes were important for clarifying the detoxification mechanism of MC-GSHs pathway. This study offers a comprehensive cognition on MCs toxicity regulation and provides valid theoretical support to control their potential risk.

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Oxidation by-products formation of microcystin-LR exposed to UV/H2O2: Toward the generative mechanism and biological toxicity

Cited by 59 publications

References 28 publications

Study of cyanotoxin degradation and evaluation of their transformation products in surface waters by LC-QTOF MS

Study of cyanotoxin degradation and evaluation of their transformation products in surface waters by LC-QTOF MS

Chlorine/UV Process for Decomposition and Detoxification of Microcystin-LR

Molecular Mechanism for the Regulation of Microcystin Toxicity to Protein Phosphatase 1 by Glutathione Conjugation Pathway

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