Biological systems selenium

Obviously the redox poise in biological systems is very important and the movement of selenium through this process has been investigated for denitrifiers such as Paracoccus denitrificans,159 a specialized selenate-respiring bacterium Thauera selenatis which used selenate as the sole electron acceptor,160,161 and phototrophic bacteria which produced different reduced forms of selenium when amended with either selenite or selenate and even added insoluble elemental Se.162 As noted above, Andreesen has commented on the importance of redox active selenocysteines135 and Jacob et al.136 note the importance of the thioredoxin system to redox poise. 

Like selenium, the process of reduction/oxidation cycling in biological systems is important and changes in the oxidation state are often an easy means of determining bioreduction for added tellurium oxyanions. The general order of... 

When one looks at the overall use of selenium in biological systems, three major pathways now emerge (Figure 1). Selenium can be derived from a large number of biologically relevant species, but most often has been studied using either selenite or L-selenocysteine as a nutritional source in model systems. These two forms... 

In this chapter, the factors influencing the distribution of metal- and metalloid-containing species are discussed, and more recent developments in understanding the behaviour of antimony, arsenic, selenium and tin in biological systems are reviewed. 

Techniques and approaches to the study of the distribution of chemical species of metals and metalloids in biological materials after sample preparation are similar to those already described for other matrices in this book, and in a recent review by Lobinski (1997). The application of these methods has led to a greater understanding of the role of metals and metalloids in biological systems. Some of the new developments in understanding the environmental behaviour of antimony, arsenic, selenium and tin are reviewed. 

Contents J.D. Odom Selenium Biochemistry - Chemical and Physical Studies. - M.Lammers, H.Follmann The Ribonucleotide Reductases - A Unique Group of Metalloenzymes Essential for Cell Proliferation. - P.H. Cornett, K.E. Wetterhahn Metabolism of the Carcinogen Chromate by Cellular Constituents. - S.Mann Mineralization in Biological Systems. 

V. N. Gladyshev, Comparison of Selenium-Containing Molybdoenzymes, in Metal Ions in Biological Systems , eds. 

Lewis, B.G., 1976. Selenium in biological systems, and pathways for its volatilization in higher plants. In J.O. Nriagu (Editor), Environmental Biogeochemistry, Vol. 1. Ann Arbor Science, Ann Arbor, pp. 389—409., ... 

At least four distinct forms of selenium have been identified in biological systems. 

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