Silver translocation

USEPA 1980). The biological half-time of silver in the lungs of an exposed person was about 1 day in liver it was 52 days (Fowler and Nordberg 1986). In humans, 80% of the retained silver in lung was cleared in about 1 day 50% of the remainder was usually cleared in 3 days (USEPA 1980). In persons who had accidentally inhaled radiosilver-llOm, most of the inhaled silver had a half-time persistence of about 1 day, probably because of rapid mucociliary clearance, swallowing, and fecal excretion most of the absorbed radiosilver translocated to the Uver (USEPA 1980). 

Anderson, P., Davidson, C. M., Littlejohn, D. etal. (1997). The translocation of caesium and silver by fungi in some Scottish soils. Communications in Soil Science and Plant... 

One of the characteristic motifs of heavy metal P-type ATPases is the CPX (commonly CPC) motif within transmembrane domain 6, widely regarded as a part of the cation channel (Silver and Phung, 1996) (Fig. 1). The possible role for these cysteines in the transmembrane domain may be the coordination of a heavy metal during its translocation through the cation channel. While these cysteines have proved to be essential for the function of some HMPAs, their exact role in catalysis is yet to be fully understood (Bissig et al., 2001 Forbes and Cox, 2000). 

Plants display a well known ability to bio-remediate heavy metals, and as a consequence have been used for nanoparticle synthesis. Presently, Gardea-Torresdey etal. demonstrated the first living plant system (Medicago sativa alfalfa plant) to bio-reduce Au + into corresponding An nanoparticles. In addition to the bio-reduction of gold, live alfalfa plants have exhibited reduction activity with silver, whereby exposure to silver containing media results in reduction to Ag , followed by absorption and uptake by the roots system, and finally translocation to the shoots as silver nanoparticles. TEM analysis shows mainly spherical nanoparticle morphologies with diameters of 2 20 nm. 

The genetic evidence presented above makes it clear that E. coli, and possibly other bacteria, possess a complex set of proteins that act in the protein-secretion process. Although it appears that at least one protein, the M13 phage coat protein, can be localized and processed in the absence of proteins other than signal peptidase (Section V,B) (Silver et al., 1981 Ohno-Iwashita and Wickner, 1983 Watts et al., 1981), most proteins of the bacterial cell envelope require the participation of a secretion apparatus for proper localization. Whether the bacterial secretion process is analogous to the eukaryotic process remains to be seen. The recent development of in vitro translocation systems derived from E. coli should facilitate research in this area (Rhoads et al., 1984 Muller and Blobel, 1984b). 

BEARLiN A R and TiKEL D (2003) Conservation genetics of Murray-Darling Basin fish silver perch Bidyanus bidyanus), Murray cod (Maccullochella peelii), and trout cod (M. macquariensis), in Phillips B (ed.). Managing fish translocation and stocking in the Murray-Darling Basin workshop, Canberra, 25-26 September 2002 statement, recommendations and supporting papers. Sydney World Wildlife Fund, 59-83. 

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