Interactions of different arsenic species with thols: Chemical and biological implications

Arsenic has been classified as a group I carcinogen. It has been ranked number one in the CERCLA priority list of hazardous substances due to its frequency, toxicity and potential for human exposure. Paradoxically, arsenic has been employed as a successful chemotherapeutic agent for acute promyelocytic leukemia and has found some success in multiple myeloma. Since arsenic toxicity and efficacy is species dependent, a speciation method, based on the complementary use of reverse phase and cation exchange chromatography, was developed. Inductively coupled plasma mass spectrometer (ICP-MS), as an element specific detector, and electrospray ionization mass spectrometer (ESI-MS), as a molecule specific detector, were employed. Low detection limits in the µg. L−1 range on the ICP-MS and mg. L−1 range on the ESI-MS were obtained. The developed methods were validated against each other through the use of a Deming plot. With the developed speciation method, the effects of both pH on the stability of As species and reduced glutathione (GSH) concentration on the formation and stability of arsenic glutathione complexes were studied. To identify arsenicals in multiple myeloma (MM) cell lines post arsenic trioxide (ATO) and darinaparsin (DAR) incubation, an extraction method based on the use of ultrasonic probe was developed. Extraction tools and solvents were evaluated and the effect of GSH concentration on the quantitation of arsenic glutathione (As-GSH) complexes in MM cell extracts was studied. The developed method was employed for the identification of metabolites in DAR incubated cell lines where the effect of extraction pH, DAR incubation concentration and incubation time on the relative distribution of the As metabolites was assessed. A new arsenic species, dimethyarsinothioyl glutathione (DMMTA V-GS), a pentavalent thiolated arsenical, was identified in the cell extracts through the use of liquid chromatography tandem mass spectrometry. The formation of the new metabolite in the extracts was dependent on the decomposition of s-dimethylarsino glutathione (DMA(GS)). These results have major implications in both the medical and toxicological fields of As because they involve the metabolism of a chemotherapeutic agent and the role sulfur compounds play in this mechanism.

Determination of Arsenic Species in Water and Grape-Based Beverages

Arsenic is a human carcinogen that has been found in various waters and wines throughout the world. Therefore, close examination of these liquids is necessary to prevent the intoxication of animals and humans. Wines and waters often contain significant amounts of toxic arsenic species. The source of arsenic in wines and waters is generally believed to be the result of arsenic-based pesticides and herbicides. Recent studies have also shown that toxic arsenic may be used in the cultivation and acceleration of the ripening process of fruit, ultimately contaminating fruit-based beverages. The determination of total arsenic can be found by using several methods, including AFS or ICP/MS. No pretreatment of water is necessary, except for filtering by means of a Fisherbrand PTFE 0.45 connected to a Becton-Dickinson 10 mL syringe to filter particles from water. The pretreatment of the wine includes ethanol evaporation and an addition of 0.1% nitric acid. A number of commercial drinking waters and regional lake water were analyzed. Since we have confirmed the presence of arsenic in a variety of waters and wines from different countries, we decided to test a number of commercially available beverages for the presence of arsenic. The focus ofthis project is to establish the presence of arsenic in various commercially available beverages. ICP-MS was used to determine total arsenic using certified standards. Internal standards Indium and Yttrium were also used to verify the concentration readings, which varied from 0- 20 ppb.

N-acetoxy-N-acetyl-2-aminofluorene binding sites on [phi] X174 and SV40

Restriction enzyme inhibition and lambda exonuclease studies indicate that carcinogen N-acetoxy-N-acetyl-2 aminofluorene (AAAF) binds to sequences on ɸX174 RF and SV40 plasmids DNA that are similar to the eight preferred binding sites previously located on pBR 322. Both DNAs were digested with enzyme Hinf I and resultant fragments 32P end-labeled. Labeled fragments were reacted with the carcinogen to give one to sixteen bound moieties per DNA. Fragments were isolated and restriccion enzyme and lambda exonuclease inhibition assays were performed. Inhibition detected occurred at selected sites and was not specific for a certain enzyme or certain size of recognition sequence. Results of these assays allow mapping of the location of high affinity binding sites of the carcinogen on both DNAs. All sites have common sequence elements: the presence of either the sequence T(G/C)TT(G/C) or the sequence T(G/C) CTT(G/C).