Oxoperoxofluoromolybdate(VI) complexes. The first synthesis of oxodiperoxofluoromolybdate(VI) complexes

A number of oxoperoxofluoromolybdate(VI) complexes, viz. M₂[MoO(O₂)F₄] and M₂[MoO(O₂)₂F₂] where M = K and NH₄ and K[MoO(O₂)₂F]·2H₂O have been synthesised by various methods. The infrared spectra suggest that the peroxide groups are bonded to the molybdenum centre in a triangular bidentate manner.     

The role of superoxide radical in chromium (VI)-generated hydroxyl radical: the Cr(VI) Haber-Weiss cycle.

To understand the role of the superoxide (O-2) radical in chromate-related genotoxicity, we investigated whether Cr(VI) can catalyze the Haber-Weiss cycle in vitro: O-2 + Cr(VI)----Cr(V) + O2 Cr(V) + H2O2----Cr(VI) + .OH + OH-. ESR and spin trapping techniques were utilized to monitor the O-2 (produced using xanthine/xanthine oxidase), .OH, and Cr(V) species. Superoxide dismutase as well as catalase inhibited the .OH radical radical formation, attesting to the direct involvement of O-2 and H2O2 in the process. ESR measurements also provided direct evidence for the formation of Cr(V). Kinetic measurements were consistent with the role of Cr(V) and H2O2 as intermediates in .OH formation. These results indicate that in cellular media, especially during chromate phagocytosis, the O-2 radical can become a significant source of .OH radicals and hence a significant factor in the biochemical mechanism of cellular damage due to Cr(VI) exposure.     

Terrorist Radiological Dispersive Device (RDD) Scenario and Cancer Risk Assessment

Terrorist attacks using radiological dispersal devices (RDD) are important threats that can lead to major environmental, economic, and public health concerns. In a simulation using a Gaussian model, we sought to determine dose curves as a function of distance from the explosion core site and from these data to determine the relative risk of developing tumors as well as the probability of causation (i.e., the statistical correlation between occurrence of malignancies and previous exposure to radiation). Calculation confirmed the cause dependence on age at exposure and the probability of tumor causation. This study aimed at emphasizing the importance of responding rapidly and efficiently, with a user-friendly user methodology that initially may help to guide the response from basic actions to the complete decision process.     

Biosorption of Chromium(VI) and Lead(II): Role of Spirulina platensis in the Treatment of Industrial Effluent

Biosorption is the process of removal of any chemical molecules by the treatment of biological material. Industrialization resulted in the discharge of various toxic heavy metals into water bodies, which poses serious health hazards to humans and animals. In the present study, live Spirulina platensis was used as a biosorbent for the removal of the heavy metals chromium (Cr(VI)) and lead (Pb(II)) from the aqueous samples. S. platensis were cultured in the presence of different concentrations of heavy metals. The growth of the algal cells was found to be decreased by 59% and 36% in media containing 50 ppm Cr(VI) and Pb(II), respectively. To assess the biosorption of heavy metals, at different time intervals, the spent culture media were used to detect Cr(VI) by atomic absorption spectroscopy method and Pb(II) by 4-(2-pyridylazo)resorcinol indicator method. Results suggested that there was a significant uptake of Cr(VI) and Pb(II) from the medium by S. platensis, with corresponding decrease of metals in the medium. When metal salt solutions or industrial effluent samples were passed through the column containing immobilized live S. platensis in calcium alginate beads, the concentration of Cr(VI) was found to be reduced drastically. The present study indicates the application of S. platensis for the bioremediation of heavy metals from the samples obtained from industrial effluents.     

Binding of chromium(VI) to histones: implications for chromium(VI)-induced genotoxicity

The first evidence has been obtained for Cr(VI) (chromate) binding to isolated calf thymus (CT) histones under physiological conditions (pH 7.4, Cl⁻ concentration 152 mM, 310 K). No significant Cr(VI) binding under the same conditions was observed for other extracellular and intracellular proteins, including albumin, apo-transferrin and G-actin, as well as for CT DNA. The mode of Cr(VI) binding to histones was studied by vibrational, electronic and X-ray absorption (X-ray absorption near-edge structure and X-ray absorption fine structure) spectroscopies and molecular mechanics calculations. A proposed binding mechanism includes electrostatic interactions of CrO₄ ²⁻ with protonated Lys and Arg residues of histones, as well as the formation of hydrogen bonds with the protein backbone. Similarly, Cr(VI) can bind to nuclear localization signals (typically, Lys- and Arg-rich fragments) of other nuclear proteins. Selective binding of Cr(VI) to newly synthesized nuclear proteins (including histones) in the cytoplasm is likely to be responsible for the active transport of Cr(VI) into the nuclei of living cells. Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users.     

The exon organization of the triple-helical coding regions of the human alpha 1(VI) and alpha 2(VI) collagen genes is highly similar.

The alpha 1(VI) and alpha 2(VI) chains, two of the three constituent chains of type VI collagen, are highly similar in size and domain structure. They are encoded by single-copy genes residing in close proximity on human chromosome 21. To study the evolution of the type VI collagen genes, we have isolated and characterized genomic clones coding for the triple-helical domains of the human alpha 1(VI) and alpha 2(VI) chains, which consist of 336 and 335 amino acid residues, respectively. Nucleotide sequencing indicates that, in both genes, the exons are multiples of 9 bp in length (including 27, 36, 45, 54, 63, and 90 bp) except for those encoding for regions with triple-helical interruptions. In addition, the introns are positioned between complete codons. The most predominant exon size is 63 bp, instead of 54 bp as seen in the fibrillar collagen genes. Of particular interest is the finding that the exon structures of the alpha 1(VI) and alpha 2(VI) genes are almost identical. A significant deviation is that a segment of 30 amino acid residues is encoded by two exons of 54 and 36 bp in the alpha 1(VI) gene, but by a single exon of 90 bp in the alpha 2(VI) gene. The exon arrangement therefore provides further evidence that the two genes have evolved from tandem gene duplication. Furthermore, comparison with the previously reported gene structure of the chick alpha 2(VI) chain indicates that the exon structure for the triple-helical domain of the alpha 2(VI) collagen is strictly conserved between human and chicken.