Luiz F. Zara

Adsorption and preconcentration of divalent metal ions in fossil fuels and biofuels: Gasoline, diesel, biodiesel, diesel-like and ethanol by using chitosan microspheres and thermodynamic approach

Biodiesel and diesel-like have been obtained from soybean oil by transesterification and thermal cracking process, respectively. These biofuels were characterized as according to ANP standards by using specific ASTM methods. Ethanol, gasoline, and diesel were purchased from a gas station. Deacetylation degree of chitosan was determined by three distinct methods (conductimetry, FTIR and NMR), and the average degree was 78.95%. The chitosan microspheres were prepared from chitosan by split-coating and these spheres were crosslinked using glutaraldehyde. The surface area of microspheres was determined by BET method, and the surface area of crosslinked microspheres was 9.2m(2)g(-1). The adsorption isotherms of cooper, nickel and zinc on microspheres of chitosan were determined in petroleum derivatives (gasoline and diesel oil), as well as in biofuels (alcohol, biodiesel and diesel-like). The adsorption order in all fuels was: Cu>Ni>Zn. The elution tests presented the following preconcentration degrees: >4.5 to ethanol, >4.4 to gasoline, >4.0 to diesel, >3.8 to biodiesel and >3.6 to diesel-like. The application of chitosan microspheres in the metal ions preconcentration showed the potential of this biopolymer to enrich fuel sample in order to be analyzed by flame atomic absorption spectrometry.

Mercury fractionation in dourada (Brachyplatystoma rousseauxii) of the Madeira River in Brazil using metalloproteomic strategies.

This paper presents the results of mercury fractionation in muscle samples of dourada (Brachyplatystoma rousseauxii) from the JIRAU Hydroelectric Power Plant in the Madeira River Basin in the Amazon region of Brazil. The proteome of the dourada muscle was separated by two-dimensional polyacrylamide gel electrophoresis (2D PAGE). The mercury present in the protein spots was determined by graphite furnace atomic absorption spectrometry (GFAAS) after acid mineralisation in an ultrasound bath. The protein spots in which the presence of mercury was detected were characterised by electrospray ionisation tandem mass spectrometry (ESI-MS/MS) after tryptic digestion. The GFAAS determinations indicated that 65% of the mercury was linked to the protein fraction with a molar mass (Mm) of less than 90 kDa. The mercury concentrations in the seven spots in which this protein fraction was present were in the range of 11.40-35.10 μg kg(-1). Based on the mercury concentrations, it was possible to estimate that the protein spots contained approximately 1-3 mercury atoms per protein molecule. The ESI-MS/MS analysis allowed characterisation of the seven protein spots as the following proteins: protein NLRC5 (molar mass=18.10, pI=6.30); 39S ribosomal protein L36 mitochondrial (molar mass=15.40, pI=8.23); N-alpha-acetyltransferase 20 (Mm=15.95, pI=8.80); Mth938 domain-containing protein (Mm=15.01, pI=9.60); ubiquitin-40S ribosomal protein S27a (Mm=9.80, pI=7.60); parvalbumin alpha (Mm=12.40, pI=3.80) and parvalbumin beta (Mm=13.10, pI=3.45).

A metalloproteomics study on the association of mercury with breast milk in samples from lactating women in the Amazon region of Brazil

This study aimed to identify metalloproteins that lose their metal ions in the presence of mercury (Hg) and bind to Hg in breast milk samples collected from the riverine population of the Madeira River, a tributary of the Amazon River. Initially, total Hg was determined from the hair of lactating women to identify individuals who were contaminated followed by a proteomic analysis of breast milk samples through two-dimensional polyacrylamide gel electrophoresis after acetone precipitation. The presence of Hg in the obtained protein spots was determined by cold vapor atomic absorption spectrometry and cold vapor atomic fluorescence spectrometry. These determinations indicated the presence of Hg in one protein spot, which was then characterized through electrospray ionization tandem mass spectrometry. Based on searches in the UniProt database, this protein spot was identified as lysozyme C.

Identification of protein biomarkers of mercury toxicity in fish

Bioaccumulative metals such as mercury are found in increasing amounts in fish and their consumers. In the region of the Madeira River, in the Brazilian Amazon, mercury (Hg) is a predominant contaminant in the aquatic ecosystem. There is therefore a need to find specific biomarkers of mercury toxicity in fish to monitor contaminations. Here, mercury-bound proteins were identified in the liver tissues of fishes Mylossoma duriventre and Brachyplatystoma rousseauxii. Mercury was quantified in liver tissue, pellets and protein spots by graphite furnace atomic absorption. Proteins were fractionated by two-dimensional polyacrylamide gel electrophoresis and identified by mass spectrometry with electrospray ionization. We identified nine proteins linked to mercury and that presented biomarker characteristics of mercury. Among the proteins identified, isoforms of parvalbumin, ubiquitin-40S ribosomal protein S27a, brain-specific angiogenesis inhibitor 1-associated protein 2-like protein 2 and betaine–homocysteine S-methyltransferase 1 are notable for having the molecular function of binding to metallic ions.

Characterization of interactions between natural organic matter and metals by tangential-flow ultrafiltration and ICP OES

O fracionamento por tamanho molecular da materia orgânica natural (MON) de amostras de agua do Parque Nacional Serra de Itabaiana (Brasil) foi utilizado para caracterizacao temporal da complexacao de ions metalicos. Um sistema de ultrafiltracao em cinco estagios foi usado para separar a MON em seis fracoes (F1: > 100; F2: 100-50; F3: 50-30; F4: 30-10; F5: 10-5; F6: > F3 > F2 = F4 > F6 > F5. As fracoes F2 e F5 foram as mais humificadas e F6 a menos humificada. Apos 30 dias com adicao de elevadas concentracoes de metais nas amostras filtradas novas distribuicoes de COD e metais foram observadas. Maior COD ainda foi encontrado na F1 com teores de carbono decrescendo na seguinte ordem: F1 > F2 > F3 > F4 > F5 > F6. Os metais apresentaram distribuicoes similares e homogeneas em todas as fracoes. Valores de log K foram similares para as amostras in natura e para aquelas de 30 dias apos a adicao dos metais (7,1 e 7,0; 6,6 e 6,9; e 7,2 e 7,0 para Al, Cu e Fe-MON, respectivamente), indicando uma nova condicao de equilibrio na distribuicao dos metais apos 30 dias. As especies formadas entre MON e os metais adicionados mostraram um modelo de distribuicao que mudou em funcao do tempo de complexacao, indicando uma transformacao dos sitios de ligacao da MON, sugerindo que o efeito coletivo das fracoes e mais importante que as propriedades individuais e confirmando que as fracoes mais humificadas exercem grande influencia na complexacao de metais em ambientes aquaticos.

Correction to: Mercury Exposure: Protein Biomarkers of Mercury Exposure in Jaraqui Fish from the Amazon Region

In the affiliation section, Luiz Fabricio Zaras affiliation “Pontifical Catholic University of Goiás (PUC), Goiânia, GO, Brazil” was incorrect. The correct affiliation is College of Planaltina, UnB - University of Brasília, Distrito Federal, Brazil