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Unique ability of BiOBr to decarboxylate d-Glu and d-MeAsp in the photocatalytic degradation of microcystin-LR in water.
Environ Sci Technol. 2011 Feb 15; 45(4):1593-600.ES

Abstract

Bismuth oxide bromide, BiOBr, was used to catalyze the degradation of microcystin-LR (MC-LR) in water at neutral pH under visible light. During the investigation, twelve intermediates from MC-LR decomposition were identified by LC-MS. In addition to attacking MC-LR at the typically susceptible sites (i.e., the conjugated double bond of the Adda chain and terminal unsaturated bond of the Mdha chain), the BiOBr photocatalyst has the remarkable ability to decarboxylate the free acid groups on d-glutamic acid (Glu) and methyl-d-aspartic acid (MeAsp). This reactivity has not been previously observed with TiO2 photocatalysis or with other MC-LR treatments in which decarboxylation does not occur until the MC-LR ring has been cleaved or mineralized to CO2. Some expected intermediate products were detected with oxygen-18 labeling by using H2(18)O as the solvent to confirm that the decarboxylation process is mediated by BiOBr. Results from characterizing the intermediates as well as oxygen-18 labeling studies indicates that oxidative decarboxylation of MC-LR by BiOBr photocatalysis is not always initiated by hydroxyl radical attack (and/or interaction with a hole followed by hydrolysis) proposed mechanism in TiO2 photocatalysis, whereas likely caused by a direct interaction between photoinduced hole of BiOBr and free carboxyl groups of MC-LR. This unusual decarboxylation behavior seems to be associated with the particular valence band and conduction band state of BiOBr photocatalyst. Also under BiOBr catalysis, a very stable guanidine group of l-arginine (l-Arg) that is nonreactive with TiO2 photocatalysis is converted to an amino group and subsequently oxidized to a nitro group during the decomposition of MC-LR. This reaction sequence is also related to decarboxylation because the guanidine conversion requires a completely or partially decarboxylated precursor. Our results indicate that BiOBr, a photocatalyst that selectively destroys sites crucial to MC-LR toxicity, shows great promise as a means of effectively treating drinking water.

Authors+Show Affiliations

Engineering Research Center of Eco-environment in Three Gorges Reservoir Region, Ministry of Education, China Three Gorges University, Hubei Yichang 443002, China.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

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

Language

eng

PubMed ID

21247106

Citation

Yanfen, Fang, et al. "Unique Ability of BiOBr to Decarboxylate d-Glu and d-MeAsp in the Photocatalytic Degradation of microcystin-LR in Water." Environmental Science & Technology, vol. 45, no. 4, 2011, pp. 1593-600.
Yanfen F, Yingping H, Jing Y, et al. Unique ability of BiOBr to decarboxylate d-Glu and d-MeAsp in the photocatalytic degradation of microcystin-LR in water. Environ Sci Technol. 2011;45(4):1593-600.
Yanfen, F., Yingping, H., Jing, Y., Pan, W., & Genwei, C. (2011). Unique ability of BiOBr to decarboxylate d-Glu and d-MeAsp in the photocatalytic degradation of microcystin-LR in water. Environmental Science & Technology, 45(4), 1593-600. https://doi.org/10.1021/es103422j
Yanfen F, et al. Unique Ability of BiOBr to Decarboxylate d-Glu and d-MeAsp in the Photocatalytic Degradation of microcystin-LR in Water. Environ Sci Technol. 2011 Feb 15;45(4):1593-600. PubMed PMID: 21247106.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Unique ability of BiOBr to decarboxylate d-Glu and d-MeAsp in the photocatalytic degradation of microcystin-LR in water. AU - Yanfen,Fang, AU - Yingping,Huang, AU - Jing,Yang, AU - Pan,Wang, AU - Genwei,Cheng, Y1 - 2011/01/19/ PY - 2011/1/21/entrez PY - 2011/1/21/pubmed PY - 2014/3/19/medline SP - 1593 EP - 600 JF - Environmental science & technology JO - Environ Sci Technol VL - 45 IS - 4 N2 - Bismuth oxide bromide, BiOBr, was used to catalyze the degradation of microcystin-LR (MC-LR) in water at neutral pH under visible light. During the investigation, twelve intermediates from MC-LR decomposition were identified by LC-MS. In addition to attacking MC-LR at the typically susceptible sites (i.e., the conjugated double bond of the Adda chain and terminal unsaturated bond of the Mdha chain), the BiOBr photocatalyst has the remarkable ability to decarboxylate the free acid groups on d-glutamic acid (Glu) and methyl-d-aspartic acid (MeAsp). This reactivity has not been previously observed with TiO2 photocatalysis or with other MC-LR treatments in which decarboxylation does not occur until the MC-LR ring has been cleaved or mineralized to CO2. Some expected intermediate products were detected with oxygen-18 labeling by using H2(18)O as the solvent to confirm that the decarboxylation process is mediated by BiOBr. Results from characterizing the intermediates as well as oxygen-18 labeling studies indicates that oxidative decarboxylation of MC-LR by BiOBr photocatalysis is not always initiated by hydroxyl radical attack (and/or interaction with a hole followed by hydrolysis) proposed mechanism in TiO2 photocatalysis, whereas likely caused by a direct interaction between photoinduced hole of BiOBr and free carboxyl groups of MC-LR. This unusual decarboxylation behavior seems to be associated with the particular valence band and conduction band state of BiOBr photocatalyst. Also under BiOBr catalysis, a very stable guanidine group of l-arginine (l-Arg) that is nonreactive with TiO2 photocatalysis is converted to an amino group and subsequently oxidized to a nitro group during the decomposition of MC-LR. This reaction sequence is also related to decarboxylation because the guanidine conversion requires a completely or partially decarboxylated precursor. Our results indicate that BiOBr, a photocatalyst that selectively destroys sites crucial to MC-LR toxicity, shows great promise as a means of effectively treating drinking water. SN - 1520-5851 UR - https://www.unboundmedicine.com/medline/citation/21247106/Unique_ability_of_BiOBr_to_decarboxylate_d_Glu_and_d_MeAsp_in_the_photocatalytic_degradation_of_microcystin_LR_in_water_ L2 - https://doi.org/10.1021/es103422j DB - PRIME DP - Unbound Medicine ER -