Alkyl Mercury Research Articles

Replacing manual operation with bio-automation: A high-throughput evolution strategy to construct an integrated whole-cell biosensor for the simultaneous detection of methylmercury and mercury ions without manual sample digestion

Methylmercury is primarily responsible for most food mercury pollution cases. However, most biosensors developed for mercury pollution analysis can only detect mercury ions. Although oxidative strong-acid digestion or microwave-assisted digestion can convert methylmercury into mercury ions, it is unsuitable for on-site detection. This study designed a bio-digestion gene circuit and integrated it into a mercury ion whole-cell biosensor，creating a novel on-site methylmercury detection method. Five alkyl mercury lyases from different bacterial genomes were screened via bioinformatics analysis, of which goMerB from Gordonia otitis showed the highest catalytic biological digestion efficiency. The goMerB site-specific saturation and random mutation libraries were constructed. After two rounds of high-throughput visualization screening, the catalytic activity of the mutant increased 2.5-fold. The distance between the three crucial amino acid sites and methylmercury changed in the mutant, which likely contributed to the enhanced catalytic efficiency. The optimized whole-cell biosensor showed a linear dynamic concentration range of 100 nM to 100 μM (R2 =0.991), satisfactory specificity, and interference resistance. The detection limit of the goMerBt6-MerR-RFP biosensor was 0.015 μM, while the limit of quantitation was 0.049 μM. This study demonstrated the application of synthetic biology for food safety detection and highlighted the future potential of “Lab in a Cell” for hazard analysis.

Quantitative detection of organic mercury in whole blood using derivatization and gas chromatographynegative chemical ionization-mass spectrometry

The Minamata disease, first identified in Japan in the 1950s, is caused by severe methylmercury (MeHg) poisoning. To prevent the development of this disease, routine evaluation of MeHg levels in blood samples is crucial. The purpose of this research was to explore the use of derivatization and capillary gas chromatography-negative chemical ionization-mass spectrometry (GC-NCI-MS) for the quantitative detection of both organic and inorganic mercury in blood samples. Alkyl mercury in standard solutions was extracted as halide salts in toluene with hydrohalic acid. Fat contents in whole blood samples were removed by methyl isobutyl ketone and hexane using a cysteine/alkaline solution and then organic mercury was extracted as a bromide complex using toluene and cupper chloride solution. The linearity of the response ratio vs. concentration curves (R2) was 0.987 for methylmercury bromide and 0.990 for ethylmercury bromide. over the calibration range of 0.02 ng/mL to 20 ng/mL. The recovery of MeHg and ethylmercury (EtHg) was 67.1% and 49.3%, respectively. The concentrations of MeHg in whole blood samples determined using GC with an electron capture detector agreed with those determined using GC-NCI-MS, with a correlation coefficient of 0.923. The mean concentration of MeHg in a certified reference material (NMIJ CRM 7402-a) determined using GC-NCI-MS was 0.64 μg/g, comparable with the certified value of 0.58 μg/g. Our study demonstrates a simple and low-cost approach for analyzing mercury in biological samples, although further optimization is required given the relatively low recovery and the concern about the toxicity of methyl isobutyl ketone.

Modification of the toxic effects of methylmercury and thimerosal by testosterone and estradiol in SH-SY5Y neuroblastoma cell line.

Short-chained alkyl mercury compounds accumulate in particularly in the brain. Exposure to these compounds is associated with various neurotoxic effects. Gender-based differences are observed in neurodevelopmental disorders, and testosterone and estradiol may alter the toxic effect of the compounds. The present study aimed to investigate the toxic effects of methylmercury and thimerosal on SH-SY5Y cells in high testosterone/low estradiol and high estradiol/low testosterone containing cellular environment and estimate whether male and female brains react differently to the toxic effects of methylmercury and thimerosal. Study groups (n = 3) were designed as control: growth medium, thimerosal (T): 1.15-μM thimerosal, methylmercury (M): 2.93-μM methylmercury, high testosterone/low estradiol + thimerosal (TT): 1-μM testosterone + 0.75-μM estradiol + 1.15-μM thimerosal, high estradiol/low testosterone + thimerosal (ET): 0.1-μM testosterone + 7.5-μM estradiol + 1.15-μM thimerosal, high testosterone/low estradiol + methylmercury (TM): 1-μM testosterone + 0.75-μM estradiol + 2.93-μM methylmercury and high estradiol/low testosterone + methylmercury (EM): 0.1-μM testosterone + 7.5-μM estradiol + 2.93-μM methylmercury. While a significant decrease in glutathione levels was observed in M group, it was not seen in EM group. A significant increase in the protein carbonyl levels was detected in T group. A similar increase was observed in the TM and TT groups in which testosterone was dominant. It was determined that methylmercury, but not thimerosal, caused significant DNA damage and in TT group. The results showed that both thimerosal and methylmercury are toxic on SH-SY5Y cells and toxic effects of methylmercury are more severe than thimerosal. It has been determined that testosterone and estradiol alter the toxic effects of thimerosal and methylmercury.

Investigation of Mercury Concentration and Existence Form in River Waters in Niigata Prefecture

The mercury concentration of river waters in Niigata Prefecture was studied for regional distribution, fluctuation factors, and speciation. We investigated 11 rivers in Niigata Prefecture four times a year. As a result, average concentrations of total mercury (T-Hg), and dissolved T-Hg in the river waters were 1.7 ng/L, and 0.29 ng/L, respectively. The average ratio of dissolved alkyl mercury concentrations to dissolved T-Hg concentrations were about 15%. The dissolved T-Hg concentrations had no observable regional differences. On the other hand, the T-Hg concentration in suspended solids (SS) was highest in the Seki River. The average T-Hg concentration in SS (SS-Hg) in the Seki River was 0.34 μg/g, whereas those in the other rivers ranged from 0.11 to 0.23 μg/g. The factor that increased SS-Hg concentration in the Seki River is considered to be the sediment originated from volcano. We investigated long-term fluctuations of T-Hg concentration in the Shinkawa River during April 2017 to March 2019. As a result, the average concentrations of dissolved T-Hg and particulate T-Hg in the Shinkawa River were 0.40 ng/L and 2.3 ng/L, respectively. The particulate T-Hg concentration was highly correlated with SS concentration.

Ultrasensitive speciation analysis of mercury in waters by headspace solid-phase microextraction coupled with gas chromatography-triple quadrupole mass spectrometry

A sensitive, repeatable and inexpensive method combining headspace solid-phase microextraction (HS-SPME) with gas chromatography-triple quadrupole mass spectrometry (GC-MS/MS) was developed for the simultaneous speciation of mercury in water samples at trace and ultra-trace levels. The low-cost home-made polydimethylsiloxane (PDMS) fiber based on sol-gel method was used as a substitute for commercial one to extract and enrich the derivatives of inorganic mercury (Hg2+), methylmercury (MeHg) and ethylmercury (EtHg) in the headspace after derivatizing with sodium tetraphenylborate (NaBPh4) in situ. Some important parameters, such as preincubation and extraction temperature, preincubation time, extraction time and inlet temperature, were investigated. Under the optimized conditions, the limits of detection (LODs) of alkyl mercury and inorganic mercury were 0.03 and 6 ng L–1, respectively. The correlation coefficients were more than 0.994 in the range of 25.0–200 ng L–1 for Hg2+ and 0.12–80.0 ng L–1 for alkyl mercury. The recoveries of the analytes in real water samples spiked at three levels were all in the range of 76.6%-114.8%. The repeatability of all mercury species was good. For inorganic mercury spiked at the lowest quality control concentration (LQC) level, the relative standard deviation (RSD) was 12.1%, and it was less than 7.7% at higher spiked concentration. The RSDs of alkyl mercury were in the range of 3.0–8.5%. The method validation demonstrated the applicability of the proposed method, and it was finally used for the determination of mercury species in surface water and wastewater samples.

Determining Discharge Characteristics and Limits of Heavy Metals and Metalloids for Wastewater Treatment Plants (WWTPs) in China Based on Statistical Methods

Industrial wastewater and sewage are both important sources of heavy metals and metalloids in urban wastewater treatment plants (WWTPs). China has made great efforts to control heavy metal and metalloid pollution by setting discharge limits for WWTPs. There is, however, limited discharge data and no systematic methodology for the derivation of discharge limits. In this study, 14 heavy metals and metalloids (Hg, alkyl mercury, As, Cd, Cr, Cr6+, Pb, Ni, Be, Ag, Cu, Zn, Mn, Se) that are listed in the Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant (GB 18918-2002) were selected for the analysis of discharge characteristics while using the supervised monitoring data from more than 800 WWTPs located in nine provinces in China. Of the 14 heavy metals and metalloids, all but alkyl mercury were detected in the discharge water. There was a high rate of detection of As, Cu, Mn, Se, and there were some samples that exceeded the standard concentrations of Cr, Cr6+, Pb, and Ni. Removal rates of Hg, As, Cd, Cr, Cr6+, Pb, Ni, Cu, Zn, Mn, and Se were higher than 40%, comparable to values from other countries. Hg and As were selected to analyze the influencing factors of effluent and derive discharge limits of WWTPs using a statistical method, because these two metals had more detected data than other metals. The study used supervised monitoring data from Zhejiang WWTPs with 99 for Hg and 112 for As. Based on the delta-lognormal distribution, the results showed that geographic location was significantly closely correlated with Hg (P = 0.027 < 0.05) and As (P ≈ 0 < 0.05) discharge concentrations, while size (for Hg P = 0.695 > 0.05, for As P = 0.088 > 0.05) and influent concentration (R2 < 0.5) were not. Derived Hg and As discharge limits suggest that it is necessary to establish stricter discharge limits for WWTPs, which is more consistent with the real-world situation in China. The study here comprehensively researches the discharge characteristics of heavy metals and metalloids in effluent of WWTPs in China, and developed for the first time in China heavy metals and metalloids discharge limits based on statistical methods. The results may inform special discharge limit settings for WWTPs in China.

Alkyl mercury compounds: an assessment of DFT methods

A series of hybrid and pure density functionals have been assessed in order to provide a reliable description of infrared spectra of alkyl mercury compounds. The theoretical assessment also includes other physicochemical properties, as ionization energies and binding energies. The accuracy of the results was tested through the available experimental data and CCSD(T) calculations. B3LYP functional provides the smallest average error of all functionals considering the whole set of properties, and it offers very good results in IR spectra in particular, although other functionals as BP86, M06-L or mPW1PW91 can give even better results when looking at one particular property. Hybrid functionals B3PW91 and X3LYP and doublehybrid B2PLYP follow B3LYP in the list of most wellbehaved functionals.

Effects of Impurities in CO2 Stream on Marine Organisms

In the event of CO2 leakage of offshore CCS, impurity substances in a CO2 stream could have potential impacts on marine organisms. Hazardous impurities, i.e. CO, SO2, H2S, NOx, NH3 and Hg were reviewed. Effects of CO and SO2 on marine organisms were scarcely known. Japanese guideline indicates safe levels<0.0009mg/L for H2S,<0.2mg/L for NO2,<30mg/L for NO3,<0.035mg/L for NH3,<0.0001mg/L for total mercury and<0.001mg/L for alkyl mercury. The impact of these impurities will likely be overshadowed by that of the leaked CO2.

ChemInform Abstract: One-Pot Alkoxymercuriation-Bromodemercuriation: A Versatile Access to 3-Alkoxy-2-bromopropanoic Esters.

Abstract A convenient one-pot methodology for the preparation of 3-alkoxy-2-bromopropanoic esters from alkyl acrylates is described. The use of stoichiometric amounts of alkyl acrylate, alcohol and mercury trifluoroacetate in THF makes this procedure versatile and attractive to achieve building blocks for the synthesis of targeted contrast agents for Magnetic Resonance Imaging.

Cleaving Alkyl Mercury

Cleaving Alkyl Mercury

Quantification and Speciation of Mercury and Selenium in Fish Samples of High Consumption in Spain and Portugal

Mercury (Hg) and selenium (Se) determinations were carried out to evaluate human exposure to those elements through fish consumption in Spain and Portugal. Atomic fluorescence spectroscopy (AFS) was applied in a cold vapor mode for total mercury quantification and was also hyphenated to gas chromatography (GC) to achieve the speciation of organomercurial species in fish samples. The results obtained show the highest concentration of Hg in swordfish and tuna (0.47+/-0.02 and 0.31+/-0.01 microg g-1, respectively), and a much lower concentration in sardine, mackerel shad, and octopus (0.048+/-0.002, 0.033+/-0.001, and 0.024+/-0.001 microg g-1, respectively). The determination of alkyl mercury compounds revealed that 93-98% of mercury in the fish samples was in the organic form. Methylmercury (MeHg) was the only species found in the three fish species with higher mercury content. Total selenium concentration was high in sardine, swordfish, and tuna (0.43+/-0.02, 0.47+/-0.02, and 0.92+/-0.01 microg g-1, respectively), but low in mackerel shad and octopus (0.26+/-0.01 and 0.13+/-0.01 microg g-1, respectively). Speciation of selenium compounds was done by high-performance liquid chromatography in conjunction with inductively coupled plasma mass spectrometry (LC-ICP-MS). Selenomethionine (SeMet) was the only selenium compound identified in the fish samples with higher selenium content. Among the fish species studied, sardine had the most favourable Se:Hg and SeMet:MeHg molar ratios; therefore, its consumption seems to be preferable.

Speciation of mercury in soil and sediment by selective solvent and acid extraction.

In order to characterize the mercury hazard in soil, a sequential extraction scheme has been developed to classify mercury species based on their environmental mobility and/or toxicity for either routine lab analysis or on-site screening purposes. The alkyl mercury species and soluble inorganic species that contribute to the major portion of potential mercury toxicity in the soil are extracted by an acidic ethanol solution (2% HCl+10% ethanol solution) from soil matrices as "mobile and toxic" species. A High-Performance Liquid Chromatography (HPLC) system coupled with Inductively Coupled Plasma Mass Spectrometry (ICP-MS) detection has been developed to further resolve the species information into soluble inorganic species (Hg(2+)), methylmercury(II) (MeHg(+)) and ethylmercury(II) (EtHg(+)) species. Alternatively, these species can be separated into "soluble inorganic mercury" and "alkyl mercury" sub-categories by Solid-Phase Extraction (SPE). A custom Sulfydryl Cotton Fiber (SCF) material is used as the solid phase medium. Optimization of the SCF SPE technique is discussed. Combined with a direct mercury analyzer (DMA-80), the SCF SPE technique is a promising candidate for on-site screening purposes. Following the ethanol extraction, the inorganic mercury species remaining in soil are further divided into "semi-mobile" and "non-mobile" sub-categories by sequential acid extractions. The "semi-mobile" mercury species include mainly elemental mercury (Hg) and mercury-metal amalgams. The non-mobile mercury species mainly include mercuric sulfide (HgS) and mercurous chloride (Hg(2)Cl(2)).

Heavy Metal Toxicity, Part I: Arsenic and Mercury

This review is Part I of a two-part series focusing on heavy metal toxicity. Part I will cover arsenic and mercury toxicity. Acute and chronic arsenic toxicity, as well as arsine gas toxicity, will be reviewed. The clinical presentation, with focus on the nervous, cardiovascular, pulmonary, gastrointestinal, hepatic, renal, hematopoietic, and dermatologic systems, is delineated. Mercury exposure, including exposure to short chain alkyl mercury, elemental mercury, and acute inorganic salt, is reviewed. The discussion of clinical toxicity focuses on the nervous, cardiovascular, pulmonary, gastrointestinal, and renal systems, as well as on the teratogenic effects of mercury. Recommendations for diagnostic tests and management plans are discussed, including chelation regimens.

Apoptotic process of cerebellar degeneration in experimental methylmercury intoxication of rats.

This report deals with the mechanism involved in the cerebellar degeneration following experimental methylmercury poisoning of male Wistar rats. The cerebellar granule cells of animals that exhibited typical hind leg paresis were shrunken and displayed marked nuclear pyknosis. At the ultrastructural level, the nuclei of these cells were condensed and fragmented, features which are characteristic of apoptosis. In situ staining for DNA strand breaks revealed that the pyknotic nuclei were positively labeled. DNA fragmentation was confirmed by agarose gel electrophoresis; a ladder pattern of multiples of approximately 200-base pair fragments, typical of apoptosis, was observed with the cerebellar DNA of the methylmercury-treated animals. These observations suggest that the degeneration of cerebellar granule cells by alkyl mercury compounds involves an apoptotic process.

Phagocytic cells as a contributor to in vivo degradation of alkyl mercury.

Phagocytic cells as a contributor to in vivo degradation of alkyl mercury.

Screen-printed electrodes for stripping measurements of trace mercury

Screen-printed carbon-strip electrodes, coated with a thin gold film, are used for highly sensitive potentiometric stripping measurements of trace levels of mercury. The stripping response toward mercury at these inexpensive and disposable electrodes compares favorably with that common at conventional gold electrodes. Various experimental variables have been optimized to yield low detection limits (e.g., 0.5 μg 1 −1 mercury for 4 min deposition) and good precision (e.g., R.S.D. of 2.5% for 20 repetitive measurements of 25 μg 1 −1 mercury). Applicability to trace measurements of alkyl mercury and selenium is also demonstrated. Such adaptation of screen-printing technology for the development of reliable sensors for trace mercury should benefit numerous field applications.

Peroxide synthesis from alkyl halides, alcohols and alkenes

New and improved methods of peroxide synthesis have been developed along with advances in peroxide analyses. Hydroperoxides were obtained by one of three methods: i) perhydrolysis of alkyl mercury tetrafluoroborates (RHgBF4); ii) perhydrolysis of alkyl trifluoromethanesulfonates (triflates, ROSO2CF3); and iii) photooxygenation of unsaturated fatty esters (methyl oleate) with sensitizer in a phase transfer catalysis (PTC) system. Dialkyl peroxides also were prepared by three methods: hydroperoxidation of the mercury and triflate intermediates and an innovation of the reaction of superoxide anion with alkyl halides in a PTC system. Chromatographic—gas‐liquid chromatography (GLC) and high‐performance liquid chromatography (HPLC)—methods were examined in detail for compositional analysis of hydroperoxides and dialkyl peroxides in reaction mixtures and for purity determinations. Dialkyl peroxides were further analyzed by an improved rapid iodometric method by using strong non‐oxidizing acid (HCLO4) and iron catalysis.

Application of SR-XRF Imaging and Micro-Xanes to Meteorites, Archaeological Objects and Animal Tissues

AbstractSynchrotron Radiation Induced X-ray Fluorescence analysis was successfully applied to the analyses of meteorites, archaeological objects and animal tissues. Electronic states of Fe and Ti in chondrules of chondrites were clarified by micro-XANES to be Fe2+ and Ti4+. Ancient iron implement (B.C. 3c A.D. 3c) with zoning of rusts was characterized by micro-XANES. Two dimensional chemical state analyses of the sample were made by selective excitation of iron. Trace element analyses of Cu, Zn, Se, and Hg in the brain and kidney of rat, mouse, and guinea pig dosed with alkyl mercury and/or Se were made from a view point of mercury intoxication. Strong correlation between Hg and Cu, Zn, Se was observed by the correlation analysis of the elemental distributions. The XRF imaging also disclosed decrease of Cu and Zn level in cancerous tissues of human kidney compared with normal ones.Advantages of Synchrotron Radiation (SR) as an X-ray source of X-ray Fluorescence (XRF) Analysis have been demonstrated by many pioneering researchers. The advantages include wavelength tunability, high intensity and high resolution, which allow us to carry out nondestructive multielemental analysis of trace elements. However, practical application of the SR-XRF is still limited in numbers. The authors expected that the application of SR-XRF is most promising in the fields of archaeological objects, geological samples, and biological samples and started the present research projects in 1987. Now we have established the analytical procedures of these samples by SR-XRF that we report a part of our results, which so far we obtained from the analyses of geological samples, archaeological objects and biological samples.The techniques of chemical state analysis used in this study are based on the following two approaches: one is XANES (X-ray absorption Near Edge Structure) and the other is SIXES (Selectively Induced X-ray Emission Spectroscopy). It is well known that the former technique together with EXAFS has been developed rapidly with the development of intense SR beams. SIXES was recently established by Sakurai et al. It enables us to carry out chemical state mapping by X-ray fluorescence using absorption edge shifts. This method was first applied to practical problems in this study.

Studies on the role of gastrointestinal tract contents in the methylation of inorganic mercury compounds.

The toxic action of the mercury compounds and their bioavailability depends on the chemical structure of the compound. It is well known that mercury compounds can be transformed into metallic mercury or to alkyl mercury compounds in the environment. This transformation caused by microorganisms was observed in the soil and human feces. Therefore, the idea that inorganic mercury ingested in small quantities with daily meals can be partly transformed into alkyl mercury compounds can not be rejected without prior experiments. Result of such studies should be of special importance, because of the exceptionally high toxicity of methylmercury ion (MeHg) and its delayed neurotoxic action especially when in utero exposure is concerned. This study aimed at the investigation of the fate of inorganic mercury compounds influenced by the contents of the gastrointestinal tract.

Laser activity of some alkyl mercury bromides

A study was made of the luminescence spectra (excited by a pulsed discharge with ultraviolet preionization) and of the absorption spectra (in the wavelength range 215–300 nm) of RHgBr vapors, where R = C2H5, iso-C4H9, and sec-C4H9. Pumping of media containing ethyl mercury bromide and isobutyl mercury bromide mixed with helium resulted in attainment of the lasing threshold for the B→X transition in HgBr molecules. The differences observed between the temperature dependences of the luminescence intensities of the investigated substances were attributed tentatively to different stabilities of RHgBr molecules exposed to the effects of a discharge plasma.