Parvalbumin and Ubiquitin as Potential Biomarkers of Mercury Contamination of Amazonian Brazilian Fish.

Recent studies have demonstrated the association of mercury (Hg) with some fish proteins, milk, and hair from individuals exposed to the element in the Amazon. However, few studies involve identifying biomarkers of mercury exposure. Therefore, the present study aimed to identify potential biomarkers of Hg exposure in fish. For this, the muscular tissues of two species of fish (Prochilodus lineatus and Mylossoma duriventre) that feed the Amazonian human population were analyzed. Through the analyses obtained by graphite furnace atomic absorption spectrometry (GFAAS), it was possible to identify four protein SPOTS where mercury was present. These SPOTS, identified by mass spectrometry (ESI-MS/MS), included parvalbumin and ubiquitin-40S ribosomal protein S27a, and these being metalloproteins with biomarker characteristics. In addition, the results show the intense Hg/protein ratio observed in the two proteins, which makes metalloproteins strong candidates for biomarkers of mercury exposure. Graphical Abstract.

Water quality in an urban environmental protection area in the Cerrado Biome, Brazil.

The environmental protection area of Lageado was created in 2001 in Campo Grande, Mato Grosso do Sul's State capital, and it constitutes a conservation unit that belongs to the Sustainable Use Group. The environmental protection area of Lageado is located in an urban area and provides approximately 12% of the water supplied to the municipality. Knowing the relationship between soil occupancy and population density, which may cause harmful effects to the quality of surface water and water resources, is fundamental. The present study aims to analyse the physical-chemical parameters of water samples collected at three different times and in six distinct points in Lageado. To verify whether the transformation of this watershed into a conservation unit resulted in the maintenance of water quality, the statistical analyses considered the significance and correlation among the following parameters: water quality index (WQI); dissolved aluminium, iron and copper; Escherichia coli; nitrate; ammoniacal nitrogen; Kjeldahl nitrogen; chemical oxygen demand; and chlorophyll α. The results show that the formal creation of the environmental protection area of Lageado did not provide the effective improvement or maintenance of its environmental conditions. Statistically, there were decreases in the WQI over the studied period, which demonstrates that the creation of a conservation unit is, in itself, not sufficient and it lacks the implementation of effective programmes and actions related to the soil use, occupancy and water quality.

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

This study presents data on the extraction and characterization of proteins associated with mercury in the muscle and liver tissues of jaraqui (Semaprochilodus spp.) from the Madeira River in the Brazilian Amazon. Protein fractionation was carried out by two-dimensional electrophoresis (2D-PAGE). Mercury determination in tissues, pellets, and protein spots was performed by graphite furnace atomic absorption spectrometry (GFAAS). Proteins in the spots that showed mercury were characterized by electrospray ionization tandem mass spectrometry (ESI-MS/MS). The highest mercury concentrations were found in liver tissues and pellets (426 ± 6 and 277 ± 4 µg kg-1), followed by muscle tissues and pellets (132 ± 4 and 86 ± 1 µg kg-1, respectively). Mercury quantification in the protein spots allowed us to propose stoichiometric ratios in the range of 1-4 mercury atoms per molecule of protein in the protein spots. The proteins characterized in the analysis by ESI-MS/MS were keratin, type II cytoskeletal 8, parvalbumin beta, parvalbumin-2, ubiquitin-40S ribosomal S27a, 39S ribosomal protein L36 mitochondrial, hemoglobin subunit beta, and hemoglobin subunit beta-A/B. The results suggest that proteins such as ubiquitin-40S ribosomal protein S27a, which have specific domains, possibly zinc finger, can be used as biomarkers of mercury, whereas mercury and zinc present characteristics of soft acids.

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

In the affiliation section, Luiz Fabricio Zara's 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.

Cyclen-based Gd3+ complexes as MRI contrast agents: Relaxivity enhancement and ligand design.

Magnetic Resonance Imaging (MRI) is a noninvasive radiology technique used to examine the internal organs of human body. It is useful for the diagnosis of structural abnormalities in the body. Contrast agents are used to increase the sensitivity of this technique. 1,4,7,10-Tetraazacyclododecane (cyclen) is a macrocyclic tetraamine. Its derivatives act as useful ligands to produce stable complexes with Gd3+ ion. Such chelates are investigated as MRI contrast agents. Free Gd3+ ion is extremely toxic for in vivo use. Upon complexation with a cyclen-based ligand, it is trapped in the preformed central cavity of the ligand resulting in the formation of a highly stable Gd3+-chelate. Better kinetic and thermodynamic stability of cyclen-based MRI contrast agents decrease their potential toxicity for in vivo use. Consequently, such agents have proved to be safest for clinical applications. Relaxivity is the most important parameter used to measure the effectiveness of a contrast agent. A number of factors influence this parameter. This article elucidates detailed strategies to increase relaxivity of cyclen-based MRI contrast agents. 1,4,7,10-Tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) and 1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid (DO3A) are two key ligands derived from cyclen. They also act as building blocks for the synthesis of novel ligands. A few important methodologies for the synthesis of DOTA and DO3A derivatives are described. Moreover, the coordination geometry of chelates formed by these ligands and their derivatives is discussed as well. Novel ligands can be developed by the appropriate derivatization of DOTA and DO3A. Gd3+-chelates of such ligands prove to be useful MRI contrast agents of enhanced relaxivity, greater stability, better clearance, lesser toxicity and higher water solubility.