Selenium

About: Selenium is a research topic. Over the lifetime, 21192 publications have been published within this topic receiving 429715 citations. The topic is also known as: Se & selen.

Temperature and nano-TiO2 controlled photochemical vapor generation for inorganic selenium speciation analysis by AFS or ICP-MS without chromatographic separation

Abstract: A simple yet ultrasensitive UV photochemical vapor generation (photo-CVG) is proposed for the speciation analysis of Se(IV) and Se(VI). The new photo-CVG, which is based on Se(IV) or Se(VI) reacting with an organic acid under different reaction conditions, can be coupled to AFS or ICP-MS for the speciation analysis of Se(IV) and Se(VI) in real samples such as table salt and water samples without chromatographic separation. At low temperature, only Se(IV) can be photochemically converted to selenium volatile species, and this is used for its selective determination; however, by using boiling water bath together with nano-TiO2 as a catalyst, both Se(IV) and Se(VI) can be photochemically converted to selenium volatile species, thus determining the total of Se(IV) and Se(VI). Therefore, Se(VI) concentration can be calculated from the difference between the total and Se(IV) concentration. Optimal reaction conditions and instrumental parameters are investigated; and the interferences from transition metals and other ions, as well as the photo-CVG mechanism, are discussed. The limits of detection range from 0.02 to 0.1 ng mL−1, depending on the kind of organic acid and the detector. The accuracy of the method is validated by determining Se(IV) in certified reference water sample. Real samples including commercial table salt, waste water and mineral water were successfully analyzed. This is a simple, relatively green, highly selective and sensitive, yet inexpensive method for the speciation analysis of Se(IV) and Se(VI).

Reduction of Selenite to Elemental Red Selenium by Pseudomonas sp. Strain CA5

Abstract: A Pseudomonas sp. that may be useful in bioremediation projects was isolated from soil. The strain is of potential value because it reduces selenite to elemental red selenium and is unusual in that it was resistant to high concentrations of both selenate and selenite. Exposure of the strain to 50, 100, and 150 mM selenite reduced growth by 28, 57, and 66%, respectively, while no change in growth was observed when the strain was exposed to 64 mM selenate, the highest level tested. Cells of the strain removed 1.7 mM selenite from the culture fluid during a 7-day incubation. A selenite reductase with a molecular weight of ~115 kD was detected in cell-free extracts and a protein with a molecular weight of ~700 kD was detected that reduced both selenate and nitrate. The bacterial isolate is a strict aerobe, reducing selenite to elemental red selenium under aerobic conditions only. Pseudomonas sp. strain CA5 might be useful as an inoculum for bioreactors used to harvest selenium from selenite-containing groundwater. 16S rRNA gene sequence alignment and fatty acid analysis were used to identify the bacterium as a novel species of Pseudomonas related to P. argentinensis, P. flavescens, and P. straminea.

Selenite and selenomethionine promote HL-60 cell cycle progression.

Abstract: The essential role of selenium (Se) in nutrition is well established. The elucidation of the mechanisms by which selenium regulates the cell cycle can lead to a better understanding of the nature of selenium's essentiality and its role in disease prevention. In this study, the effects of selenium deficiency or adequacy (0.25 micromol/L selenite or selenomethionine) on HL-60 cell cycle progression were examined in serum-free media. Selenium was critical for promotion of HL-60 cell growth. Cell-cycle analysis revealed that selenium deficiency caused a decrease in G1 phase cells that corresponded to an increase in G2 and sub-G1 phase cells. Gene array analysis suggested that c-Myc, cyclin C, proliferating cell nuclear antigen, cyclin-dependent kinase (cdk)1, cdk2, cdk4, cyclin B and cyclin D2 mRNA levels were lower in selenium-deficient cells than in the cells supplemented with 0.25 micromol/L selenomethionine. The decrease in the c-Myc mRNA level in selenium-deficient cells was confirmed by reverse transcription-polymerase chain reaction analysis. Furthermore, the phosphorylation state of total cellular protein was higher (57%) in selenium-supplemented cells than in selenium-deficient cells. Collectively, these results suggest a novel role for selenium at 0.25 micromol/L in up-regulation of the expression of numerous cell cycle-related genes and total cellular phosphorylated proteins in HL-60 cells in serum-free culture media. This leads to the promotion of cell cycle progression, particularly G2/M transition and/or the reduction of apoptosis, primarily in G1 cells. These observations may have additional implications for understanding the nature of selenium's essentiality.

Chemical Form and Distribution of Mercury and Selenium in Edible Seafood

Abstract: The content, chemical form, and distribution of mercury and selenium in edible tissue were determined for several samples of fish and other marine animal organisms (mollusks, crustaceans and pods). For most fish samples, except Pacific blue marlin, 53 to 94% of the total mercury content was present as methylmercury, being notably higher in freshwater species. Other marine organisms, except shrimp, contained only 29 to 47% methylmercury. For all samples, a significant part of the total selenium content (4 to 47%) was present as selenate (Se VI). Tissue selenium levels did not correlate with corresponding mercury levels. In freshwater and older processed (canned) marine fish, except marlin, 55 to 80% of the total mercury content was water-extractable. For non-processed (fresh) and newly-processed marine samples, only 22 to 47% was extractable. On a percentage basis, inorganic mercury was generally more extractable than methylmercury. For all fish samples, except marlin, 55 to 60% of the total selenium content was water-extractable, while only 35 to 45% was extractable for other marine species. On a percentage basis, Se VI was more extractable than selenite (Se IV) and selenide (Se II).