Photomethylation of inorganic mercury by aliphatic α-amino-acids

Hayashi, Kyozo; Kawai, Shinya; Ohno, Takeo; Maki, Y.

doi:10.1039/c39770000158

Cited by 21 publications

(16 citation statements)

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“…Two different mechanisms have been proposed for the photomethylation of Hg 2+ in previous studies: free radical pathways (Oldekop et al, 1960;Hayashi et al, 1977) and an intra-molecular methyl transfer of the Hg…”

Section: Mechanism Of Photo-alkylation Of Inorganic Hgmentioning

confidence: 99%

Possible alkylation of inorganic Hg(II) by photochemical processes in the environment

et al. 2012

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a b s t r a c tThe methylation of inorganic Hg by anaerobic bacteria in aquatic environments is considered to be the major pathway for methylmercury (MeHg) production. However, recent research has suggested that abiotic or chemical methylation by humic substances and other low-molecular-weight organic compounds in natural environments is also possible. Here, the aqueous photo-transformation of Hg 2+ to organomercurials was investigated in the presence of ketones, aldehydes and low molecular weight organic acids under UV irradiation. MeHg and/or ethylmercury (EtHg) were identified as the main organomercurial products by multiple analytical techniques, including chromatography-atomic spectrometry and molecular mass spectrometry and further confirmed by stable isotope tracer experiments. The yield of organomercurials was markedly influenced by pH, NaCl concentration, alkylation donor concentration and the presence of chelating ligands in the aqueous solution. Electron paramagnetic resonance spectrometry demonstrated that the radical reaction was not the predominating alkylation pathway, although methyl radicals were detected in the photo-alkylation procedure. A mechanism based on intra-molecular alkyl transfer in the Hg 2+-low-molecular-weight organic compound complex is proposed. The present work helps us better understand of MeHg and EtHg photo-generation in natural environments.

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Section: Mechanism Of Photo-alkylation Of Inorganic Hgmentioning

confidence: 99%

Possible alkylation of inorganic Hg(II) by photochemical processes in the environment

et al. 2012

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“…However, abiotic methylation is generally thought to be of little importance in most aquatic systems (Ullrich et al 2001). Another possible avenue of abiotic methylation is photomethylation under UV radiation-a process that has been identified in vitro (Akagi et al 1974;Hayashi et al 1977), but the exact mechanism of which remains unclear (Chen et al 2015). The noted simultaneous production and degradation of MeHg may result in MeHg in sediments being in steady-state (Pak and Bartha 1998); however, levels in biota may be much higher due to bioaccumulation (Ullrich et al 2001).…”

Section: Why Is Net Methylmercury Production Important and How It Is mentioning

confidence: 99%

Recent advances in the study of mercury methylation in aquatic systems

Paranjape

Hall

2017

FACETS

121

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With increasing input of neurotoxic mercury to environments as a result of anthropogenic activity, it has become imperative to examine how mercury may enter biotic systems through its methylation to bioavailable forms in aquatic environments. Recent development of stable isotope-based methods in methylation studies has enabled a better understanding of the factors controlling methylation in aquatic systems. In addition, the identification and tracking of the hgcAB gene cluster, which is necessary for methylation, has broadened the range of known methylators and methylation-conducive environments. Study of abiotic factors in methylation with new molecular methods (the use of stable isotopes and genomic methods) has helped elucidate the confounding influences of many environmental factors, as these methods enable the examination of their direct effects instead of merely correlative observations. Such developments will be helpful in the finer characterization of mercury biogeochemical cycles, which will enable better predictions of the potential effects of climate change on mercury methylation in aquatic systems and, by extension, the threat this may pose to biota.

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“…Many chemicals, e.g., amino acids [77], humic substances [53,55,58], silicones [78], and low molecular weight organic acids [66], were found to be able to methylate inorganic mercury in lab settings. Irradiance is necessary for some of these reactions [66,77].…”

Section: Methylationmentioning

confidence: 99%

Progress in the study of mercury methylation and demethylation in aquatic environments

Cai

2012

Chin. Sci. Bull.

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Mercury (Hg) and its compounds are a class of highly toxic and pervasive pollutants. During the biogeochemical cycling of Hg, methylmercury (MeHg), a potent neurotoxin, can be produced and subsequently bioaccumulated along the food chain in aquatic ecosystems. MeHg is among the most widespread contaminants that pose severe health risks to humans and wildlife. Methylation of inorganic mercury to MeHg and demethylation of MeHg are the two most important processes in the cycling of MeHg, determining the levels of MeHg in aquatic ecosystems. This paper reviews recent progress on the study of Hg methylation and demethylation in aquatic environments, focusing on the following three areas: (1) sites and pathways of Hg methylation and demethylation, (2) bioavailability of Hg species for methylation and demethylation, and (3) application of isotope addition techniques in quantitatively estimating the net production of MeHg. mercury cycling, methylation, demethylation, bioavailability, methyl mercury Citation:Li Y B, Cai Y. Progress in the study of mercury methylation and demethylation in aquatic environments.

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Photomethylation of inorganic mercury by aliphatic α-amino-acids

Cited by 21 publications

References 0 publications

Possible alkylation of inorganic Hg(II) by photochemical processes in the environment

Possible alkylation of inorganic Hg(II) by photochemical processes in the environment

Recent advances in the study of mercury methylation in aquatic systems

Progress in the study of mercury methylation and demethylation in aquatic environments

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