Comparative Analysis of Metal Binding Characteristics of Copper Chaperone Proteins, Atx1 and ATOX1

The metal binding properties of the human copper chaperone ATOXI and its yeast homologue Atxl have been characterized. Complexes of these proteins with Cu(I), Ag (1), Cd(II) and Hg(II) were studied by native gel electrophoresis, chemical cross-linking followed by SDS-PAGE, as well as by size exclusion chromatography, mutagenesis and UV-visible absorption spectroscopy. Results indicate that binding of different metals to either ATOXI or Atxl altered conformation of subunit structure and the oligomerization state of the proteins. Furthermore, it has been demonstrated that freshly reduced apoprotein is capable to convert Cu(ll) to Cu(l) stoichiometrically to the amount of protein present, while oxidized protein is only twenty per cent as active. Titration of Cu(ll) with either oxidized or reduced protein resulted in similar increase in absorbance at 254 nm, implicating Cu-thiolate formation in both forms of the protein, but titration with Ag(i) caused the increase in absorbance at 254 nm with the reduced protein only. These data indicate that Cu(1), Ag(1), Hg(ll) and Cd(ll) are all capable of binding to ATOXI and Atxl, but the characteristics of the binding to these copper chaperones differ for different metals

The Development and Use of an Innovative Laboratory Method for Measuring Arsenic in Drinking Water from Western Bangladesh

All of Bangladesh’s approximately 10 million drinking-water tube wells must be periodically tested for arsenic. The magnitude of this task and the limited resources of Bangladesh have led to the use of low-cost, semiquantitative field kits that measure As to a relatively high 50 μg/L national drinking water standard. However, there is an urgent need to supplement and ultimately replace these field kits with an inexpensive laboratory method that can measure As to the more protective 10 μg/L World Health Organization (WHO) health-based drinking water guideline. Unfortunately, Bangladesh has limited access to atomic absorption spectrometers or other expensive instruments that can measure As to the WHO guideline of 10 μg/L. In response to this need, an inexpensive and highly sensitive laboratory method for measuring As has been developed. This new method is the only accurate, precise, and safe way to quantify As < 10 μg/L without expensive or highly specialized laboratory equipment. In this method, As is removed from the sample by reduction to arsine gas, collected in an absorber by oxidation to arsenic acid, colorized by a sequential reaction to arsenomolybdate, and quantified by spectrophotometry. We compared this method with the silver diethyldithiocarbamate [AgSCSN(CH(2)CH(3))(2)] and graphite furnace atomic absorption spectroscopy (GFAAS) methods for measuring As. Our method is more accurate, precise, and environmentally safe than the AgSCSN(CH(2)CH(3))(2) method, and it is more accurate and affordable than GFAAS. Finally, this study suggests that Bangladeshis will readily share drinking water with their neighbors to meet the more protective WHO guideline for As of 10 μg/L

World Health Organization Discontinues Its Drinking-Water Guideline for Manganese

Background: The World Health Organization (WHO) released the fourth edition of Guidelines for Drinking-Water Quality in July 2011. In this edition, the 400-µg/L drinking-water guideline for manganese (Mn) was discontinued with the assertion that because “this health-based value is well above concentrations of manganese normally found in drinking water, it is not considered necessary to derive a formal guideline value.