Arsenic biology

The presence of suitable reductants (or oxidants) is essential. These effects are examined here for As(III)/As(V) and Cr(III)/ Cr(VI). The redox states of trace elements affect their solubility (e.g., Cr(III)/Cr(VI)) and their affinity for binding to solid phases (e.g., arsenite and arsenate). Biological effects (e.g., uptake and toxicity) are also dependent on the redox state. 

Chemical Weapons Suspected CW Arsenal Biological Weapons South Korea China (PRC)... 

Kampfmittel in Deutschland von 1915 bis 1945 [Biological Weapons—Not in Hitler s Arsenal Biological and Toxin War Materials in Germeiny from 1915 through 1945]. Munster LIT Verlag, 1998. 

Cobalt compounds have been in use for centuries, notably as pigments ( cobalt blue ) in glass and porcelain (a double silicate of cobalt and potassium) the metal itself has been produced on an industrial scale only during the twentieth century. Cobalt is relatively uncommon but widely distributed it occurs biologically in vitamin B12 (a complex of cobalt(III) in which the cobalt is bonded octahedrally to nitrogen atoms and the carbon atom of a CN group). In its ores, it is usually in combination with sulphur or arsenic, and other metals, notably copper and silver, are often present. Extraction is carried out by a process essentially similar to that used for iron, but is complicate because of the need to remove arsenic and other metals. 

Capillary Electrophoresis. Capillary electrophoresis (ce) or capillary 2one electrophoresis (c2e), a relatively recent addition to the arsenal of analytical techniques (20,21), has also been demonstrated as a powerful chiral separation method. Its high resolution capabiUty and lower sample loading relative to hplc makes it ideal for the separation of minute amounts of components in complex biological mixtures (22,23). 

Silver compounds having anions that are inherently toxic, eg, silver arsenate and silver cyanide, can cause adverse health effects. The reported rat oral LD values for silver nitrate, silver arsenate [13510-44-6] and silver cyanide are 500—800 (29), 200—400 (29), and 123 mg/kg (30), respectively. Silver compounds or complexes ia which the silver ion is not biologically available, eg, silver sulfide and silver thiosulfate complexes, are considered to be without adverse health effects and essentially nontoxic. 

Silver diethyldithiocarbamate [1470-61-7] is a reagent commonly used for the spectrophotometric measurement of arsenic in aqueous samples (51) and for the analysis of antimony (52). Silver iodate is used in the determination of chloride in biological samples such as blood (53). 

From a practical point of view, saturation of elimination has important consequences. If the metabolism becomes saturated, the duration of the action of the compound is prolonged. In such a case, correct timing for collection of biological monitoring samples also becomes difficult to assess. Furthermore, saturation of metabolism may also have qualitative effects. For example, it has been argued (but not yet proved) that arsenic compounds cause cancer at high doses at which methylation of inorganic arsenic becomes saturated. ... 

The striking constitution of brevetoxin B, unprecedented at the time of its discovery in 1981, presents a formidable challenge to organic synthesis. The unique and fascinating molecular architecture of brevetoxin B (1), its association with the red tide catastrophes, its potent biological activity, and the prospects for expanding the arsenal of synthetic methods all contributed in roughly equal measure to our decision to pursue a total synthesis of 1. This chapter addresses the efforts that culminated in the total synthesis of brevetoxin B (1 ).6... 

One form of biological poisoning mirrors the effect of lead on a catalytic converter. The activity of an enzyme is destroyed if an alien substrate attaches too strongly to the enzyme s active site, because then the site is blocked and made unavailable to the true substrate (Fig. 13.42). As a result, the chain of biochemical reactions in the cell stops, and the cell dies. The action of nerve gases is believed to stem from their ability to block the enzyme-controlled reactions that allow impulses to travel through nerves. Arsenic, that favorite of fictional poisoners, acts in a similar way. After ingestion as As(V) in the form of arsenate ions (As043 ), it is reduced to As(III), which binds to enzymes and inhibits their action. 

The biological cycle of arsenic in the surface ocean involves the uptake of arsenate by plankton, the conversion of arsenate to a number of as yet unidentified organic compounds, and the release of arsenite and methylated species into the seawater. Biological demethylation of the methyl-arsenicals and the oxidation of arsenite by as yet... 

Andreae, M. O. (1979). Arsenic speciation in seawater and interstitial waters the role of biological-chemical interactions on the chemistry of a trace element. Limnol. Oceanog. 24,440-452. 

HOCl is one of the oxidants that activated phagocytes have in their arsenal. Hu et al. (1993) have shown that plasma albumin sulphydryl and ascorbic acid both protect against oxidant injury from HOCl. Neutrophils, interestingly, contain about 25 times more ascorbic acid than plasma. This su ests an endogenous self-protection role. This work is important because of the biological emphasis of reactive chlorine by the neutrophil. 

The arsenic compounds most commonly found in environmental and biological materials, and in working places, are arsenite and arsenate ions [As(III) and As(V)], monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), arsine, di- and tri-... 

Stoeppler M, Vahter M (1994) Arsenic. In Herber RFM, Stoeppler M, eds. Trace element analysis in biological specimens. Elsevier, Amsterdam. 

As seen in the above equations, the aqueous oxidation processes convert sulfur in the feed to dissolved sulfate, while arsenic is oxidized and precipitated as ferric arsenate compounds. So, problems of the emission of sulfur and arsenic oxides caused by roasting are avoided in the aqueous oxidation processes. The two different industrial methods which achieve the oxidation reactions are pressure oxidation and biological oxidation. 

Tolerance in insects to increasing amounts of DDT, BHC, and several of the inorganic agents, such as arsenic, is known to occur. However, in animals, this phenomenon has not been demonstrated to the same degree. Ability of the cells of insects to function in the environment of a toxic agent, without alteration of cellular function, is one of the most striking of biologic phenomena. 

Heavy metals with no known biological function, such as aluminum, arsenic, lead, and mercury, are nonessential metals.4-5 These metals are toxic because they can irreversibly bind to enzymes that require metal cofactors. Toxic metals readily bind to sulfhydryl groups of proteins.6-7 In fact,... 

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