Phenylarsonic Acid Research Articles

Concentrations and speciation of arsenic in groundwater polluted by warfare agents

Groundwater polluted with phenylarsenicals from former warfare agent deposits and their metabolites was investigated with respect to the behavior of relevant arsenic species. Depth profiles at the estimated source and at about 1 km downgradient from the source zone were sampled. The source zone is characterized by high total arsenic concentrations up to 16 mg L −1 and is dominated by organic arsenic compounds. The concentrations in the downgradient region are much lower (up to 400 μg L −1) and show a high proportion of inorganic arsenic species. Iron precipitation seems to be an effective mechanism to prevent dispersion of inorganic arsenic as well as phenylarsonic acid. Reductive conditions were observed in the deeper zone with predominant occurrence of trivalent arsenic species. The inorganic species are in redox equilibrium, whereas the phenylarsenic compounds have variable proportions. Methylphenylarsinic acid was identified in groundwater in traces which indicates microbial degradation activity.

Comparison in thermal behaviors of homologues, derivatives and adducts of β-cyclodextrin

The thermal behaviors of homologues, derivatives and adducts of β-cyclodextrin ( β-CD) are compared based on thermogravimetry (TG) and gas chromatography coupled to time-of-flight mass spectrometry (GC–TOF-MS) analysis. Our results indicate that the number of glucose units and the introduced groups cause a considerable change in thermal decomposition mechanisms of these carbohydrates. Further, it is observed that the mass loss of the bicomponent aggregate formed by phenylarsonic acid (PAA) and β-CD is larger than that of each of the components at higher temperatures. Additionally, the decomposition of the adduct produces a series of arsenic compounds with high relative abundances, such as AsO +, As 2O 2 +, As 3O 4 + and As 4O 6 +, which is rather different from the decomposition behaviors of free PAA and the adduct of β-CD with sodium arsenite.

Do Spiroarsoranes Exhibit Polytopal Equilibrium in Solution?

The spiroarsoranes 5-phenyl-1,6-dioxa-4,9-diaza-5lambda(5)-arsaspiro[4.4]nonane (6), (3R,8R)-3,8-dimethyl-5-phenyl-1,6-dioxa-4,9-diaza-5lambda(5)-arsaspiro[4.4]nonane (7), (2S,7S)-2,7-dimethyl-5-phenyl-1,6-dioxa-4,9-diaza-5lambda(5)-arsaspiro[4.4]nonane (8), and (3S,8S)-3,8-dimethyl-(2R,7R)-2,5,7-triphenyl-1,6-dioxa-4,9-diaza-5lambda(5)-arsaspiro[4.4]nonane (9) were prepared by reaction of phenylarsonic acid and the correspondig amino alcohol. The presence of polytopal Delta left arrow over right arrow Lambda equilibrium in 6-9 was demonstrated by HPLC and NMR studies. NBO computations at the MP2/6-31+G(2d,2p) level indicate that methyl substitution in C2 or C3 of the oxazarsolane ring determines the predominance of Delta or Lambda stereoisomers. GIAO B3LYP/6-311++G(2d,2p) computations were used to assign experimental (1)H and (13)C NMR spectra.

TiO 2 photocatalytic degradation of phenylarsonic acid

Phenyl substituted arsenic compounds are widely used as feed additives in the poultry industry and have become a serious environmental concern. We have demonstrated that phenylarsonic acid (PA) is readily degraded by TiO 2 photocatalysis. Application of the Langmuir–Hinshelwood kinetic model for the initial stages of the TiO 2 photocatalysis of PA yields an apparent rate constant ( k r ) of 2.8 μmol/L min and the pseudo-equilibrium constant ( K) for PA is 34 L/mmol. The pH of the solution influences the adsorption and photocatalytic degradation of PA due to the surface charge of TiO 2 photocatalyst and speciation of PA. Phenol, catechol and hydroquinone are observed as the predominant products during the degradation. The roles of reactive oxygen species, OH, 1O 2, O 2 − and h VB + were probed by adding appropriate scavengers to the reaction medium and the results suggest that OH plays a major role in the degradation of PA. By-product studies indicate the surface of the catalyst plays a key role in the formation of the primary products and the subsequent oxidation pathways leading to the mineralization to inorganic arsenic. TiO 2 photocatalysis results in the rapid destruction of PA and may be attractive for the remediation of a variety of organoarsenic compounds.

Biodegradation of diphenylarsinic acid to arsenic acid by novel soil bacteria isolated from contaminated soil

Microorganisms capable of degrading diphenylarsinic acid (DPAA) were enriched from contaminated soil using the soil-charcoal perfusion method. Two novel bacterial strains, L2406 and L2413, that can degrade DPAA in a mineral salt medium supplemented with DPAA as the sole carbon source were isolated. Based on comparative morphology, physiology, and comparison of the 16S rRNA gene sequences, both were presumed to be species closely related to Ensifer adhaerens. As the metabolites, phenylarsonic acid (PAA) was determined by liquid chromatography-mass spectrometry analysis as well as three unknown peaks all of whose molecular weights were estimated to be 278. The increase of m/z = 16 from DPAA in the unknowns suggests monohydroxylation of DPAA at the 2-, 3- and 4-positions. The ability of strains L2406 and L2413 to degrade DPAA was suppressed in iron insufficient conditions, e.g. less than 7.2 muM iron in the culture medium. These facts strongly suggest the following hypothesis: Monooxygenase works at the initial degradation step of DPAA degradation by the isolates; and direct hydrolysis from DPAA to PAA is not likely to occur. In addition, release of arsenic acid from PAA by strain L2406 was confirmed by liquid chromatography-inductively coupled plasma mass spectrometry. From these results, strain L2406 was considered to be capable of degrading DPAA to arsenic acid via PAA when DPAA was supplied as the sole carbon source.

Methanogenic inhibition by roxarsone (4-hydroxy-3-nitrophenylarsonic acid) and related aromatic arsenic compounds

Roxarsone (4-hydroxy-3-nitro-phenylarsonic acid) and p-arsanilic acid (4-aminophenylarsonic acid) are feed additives widely used in the broiler and swine industry. This study evaluated the inhibitory effect of roxarsone, p-arsanilic, and other phenylarsonic compounds on the activity of acetate- and H(2)-utilizing methanogenic microorganisms. Roxarsone, p-arsanilic, and 4-hydroxy-3-aminophenylarsonic acid (HAPA) inhibited acetoclastic and hydrogenotrophic methanogens when supplemented at concentrations of 1mM, and their inhibitory effect increased sharply with incubation time. Phenylarsonic acid (1mM) inhibited acetoclastic but not H(2)-utilizing methanogens. HAPA, a metabolite from the anaerobic biodegradation of roxarsone, was found to be sensitive to autooxidation by oxygen. The compound (2.6mM) caused low methanogenic inhibition (only 14.2%) in short-term assays of 12h when autooxidation was prevented by supplementing HAPA solutions with ascorbate. However, ascorbate-free HAPA solutions underwent spontaneous autooxidation in the presence of oxygen, leading to the formation of highly inhibitory compounds. These results confirm the microbial toxicity of organoarsenic compounds, and they indicate that biotic as well as abiotic transformations can potentially impact the fate and microbial toxicity of these contaminants in the environment.

Natural Attenuation Potential of Phenylarsenicals in Anoxic Groundwaters

The extensive production of chemical warfare agents in the 20th century has led to serious contamination of soil and groundwater with phenyl arsenicals at former ammunition depots or warfare agent production sites worldwide. Most phenyl arsenicals are highly toxic for humans. The microbial degradation of phenylarsonic acid (PAA) and diphenylarsinic acid (DPAA) was investigated in microcosms made of anoxic groundwater/sediment mixtures taken from different depths of an anoxic, phenyl arsenical contaminated aquifer in Central Germany. DPAA was not transformed within 91 days incubation time in any of the microcosms. The removal of PAA can be described by a first order kinetics without a lag-phase (rate: 0.037 d(-1)). In sterilized microcosms, PAA concentrations always remained stable, demonstrating that PAA transformation was a biologically mediated process. PAA transformation occurred under sulfate-reducing conditions due to sulfate consumption and production of sulfide. The addition of lactate (1 mM), a typical substrate of sulfate-reducing bacteria, increased the transformation rate of PAA significantly up to 0.134 d(-1). The content of total arsenic was considerably reduced (> 75%). Intermediates of PAA transformation were detected by high performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICP-MS). Experiments with a pure strain and sterile controls of Desulfovibrio gigas spiked with PAA showed that the elimination process is linked to the presence of sulfide formed through bacterial activity. Phenyl arsenicals were likely immobilized in the sedimentthrough sulfur substitution and a subsequent sulfur bond under the prevailing sulfate reducing condition. The results of this study indicate that PAA can undergo microbiologically mediated transformation in anoxic aquifers, leading to reduced concentrations in groundwater, which indicate a (enhancend) natural attenuation potential.

Tetrachlorophenyl‐λ5‐arsane and Tetramethoxyphenyl‐λ5‐arsane: Crystal Structures, NMR Spectra and Bonding Situation

AbstractTwo phenyl‐substituted λ5‐arsanes were prepared from phenylarsonic acid in two‐step procedures. Their molecular structures were determined by single‐crystal X‐ray diffraction. NBO analyses for the title compounds were conducted.

Carbonic anhydrase inhibitors. Inhibition of the β-class enzyme from the pathogenic yeast Candida glabrata with anions

A β-carbonic anhydrase (CA, EC 4.2.1.1), the protein encoded by the NCE103 gene of Candida glabrata which also present in Candida albicans and Saccharomyces cerevisiae, was cloned, purified, characterized kinetically and investigated for its inhibition by a series simple, inorganic anions such as halogenides, pseudohalogenides, bicarbonate, carbonate, nitrate, nitrite, hydrogen sulfide, bisulfite, perchlorate, sulfate and some isosteric species. The enzyme showed significant CO 2 hydrase activity, with a k cat of 3.8 × 10 5 s −1 and k cat/ K M of 4.8 × 10 7 M −1 s −1. The Cà glabrata CA (CgCA) was moderately inhibited by metal poisons (cyanide, azide, cyanate, thiocyanate, K Is of 0.60–1.12 mM) but strongly inhibited by bicarbonate, nitrate, nitrite and phenylarsonic acid ( K Is of 86–98 μM). The other anions investigated showed inhibition constants in the low millimolar range, with the exception of bromide and iodide ( K Is of 27–42 mM).

Adsorption behavior of uranium(VI) and other ionic species on cross-linked chitosan resins modified with chelating moieties

Cross-linked chitosan resins with catechol (catechol-type chitosan, type 1 and type 2), iminodiacetic acid (IDA-type chitosan), iminodimetylphosphonic acid (IDP-type chitosan), phenylarsonic acid (phenylarsonic acid-type chitosan), or serine (serine-type chitosan) were prepared for the collection and concentration of uranium(VI). The adsorption behavior of U(VI) and other ionic species, such as metal ions and oxo-acid ions, on the cross-linked chitosan (base material) and chitosan resins modified with chelating moieties was examined using a column procedure. Especially, the catechol-type chitosan (type 2) adsorbed U(VI) at pH 2–7, and selectively collected U(VI) at acidic pH regions by forming a stable chelate with hydroxyl groups of catechol moiety introduced to the chitosan. Also, the adsorption properties of cationic and anionic species present in aquatic media were elucidated. The adsorption ability for U(VI) was in the order: catechol-type chitosan (type 2) > serine-type chitosan > phenylarsonic acid-type chitosan > the others. The catechol-type chitosan (type 2) was useful for the collection and concentration of uranium(VI).

Structure-effect relationship in the down-regulation of glutaminase in cultured human cells by phenylarsenic compounds

Diphenylarsinic acid [DPAA(V)] was detected in ground water used as drinking water after a poisonous incident in Kamisu, Japan. An approach to define the target molecules of DPAA(V) with a high throughput analysis of proteins from cultured human cells demonstrated down-regulation of glutaminase C (GAC). GAC is a splicing variant of the kidney-type glutaminase (KGA) gene and has the enzyme activity of phosphate-activated glutaminase (PAG). To gain some insights into the mechanism of arsenic intoxication in Kamisu, the effects of various arsenic compounds, including arsenicals that were detected in ground water ([DPAA(V)], phenylarsonic acid [PAA(V)] and bis(diphenylarsine)oxide [BDPAO(III)]) and rice (phenylmethylarsinic acid [PMAA(V)]), were investigated for the expression of GAC and PAG activity. When cultured human HepG2 cells were incubated with arsenicals for 24 h, the pentavalent phenylarsenic form of PAA(V) and PMAA(V) as well as DPAA(V) suppressed the expression of GAC protein and PAG activity in a concentration-dependent manner. On the other hand, the trivalent phenylarsenic form of BDPAO(III) had no suppressive effect on GAC and PAG. In addition, trivalent phenylarsenic compounds, such as the glutathione (GSH) conjugate of DPAA(V) [DPA-GS (III)] and triphenylarsine [TPA(III)], and the inorganic arsenics, iAs(V) and iAs(III), and methylated metabolites of inorganic arsenics, dimethylarsinic acid [DMA(V)] and dimethylarsinous acid [DMA(III)], had no suppressive effect on glutaminase. Likewise, methyl substituents of the hydroxyl groups of DPAA(V), PAA(V) and PMAA(V), diphenylmethylarsine oxide [DPMAO(V)] and phenyldimethylarsine oxide [PDMAO(V)], did not have any suppressive effects. These results suggest that pentavalent arsenic compounds with both phenyl groups and hydroxyl groups are effective in the suppression of glutaminase. In addition, the fact that it was only the arsenicals detected in Kamisu that were effective in suppressing glutaminase provides insights into the cause of the arsenic intoxication at Kamisu.

Uptake of Aromatic Arsenicals from Soil Contaminated with Diphenylarsinic Acid by Rice

Chemical warfare agents containing aromatic arsenicals (AAs) such as Clark I (diphenylchloroarsine) are well-known, as is the risk of leakage from such munitions into the environment. We investigated the uptake of AAs in agricultural soils by rice. Methylphenylarsinic acid (MPAA) was detected in brown rice grown in contaminated soil. Dimethylphenylarsine oxide (DMPAO) and methyldiphenylarsine oxide (MDPAO) were detected in the straw but not in the grains grown in the contaminated soil. Inthe contaminated soil, phenylarsonic acid (PAA) and MPAA concentrations decreased and DMPAO concentration increased under the flooded conditions; however, their concentrations remained unchanged underthe upland conditions. DMPAO was detected in the straw of the rice grown in PAA- or MPAA-amended soil but was not detected in that grown in a PAA- or MPAA-added solution culture. MDPAO was detected in the straw of the rice grown in diphenylarsinic acid (DPAA)-amended soil but was not detected in that grown in a DPAA-added solution culture. Thus, MPAA and DPAA were methylated not in the rice plant but in the soil under the flooded conditions. Dephenylated products were detected in the straw grown in AA-added solution cultures, but demethylated products were not detected. DMPAO and MDPAO absorbed by the shoots were retained, and MPAA and DPAA absorbed by the shoots were translocated to the grains more easily than other AAs.

Cytotoxicity of arsenic-containing chemical warfare agent degradation products with metallomic approaches for metabolite analysis

The arsenic metallome in African Green Monkey kidney cells is probed by measuring cytotoxicity, cellular arsenic uptake and speciation studies on arsenic-containing chemical warfare agent degradation products (CWDPs) during cell uptake. Inorganic arsenic compounds and methylated species also were studied during cell uptake as a means of providing cytotoxicity information relative to the CWDPs. The degradation products used were phenylarsine oxide (PAO), phenylarsonic acid (PAA), diphenylarsinic acid (DPAA), triphenylarsine (TPA) and triphenylarsine oxide (TPAO). These are the warfare agent’s primary degradation products. The parent warfare agents (red agents) are diphenylarsine chloride (DA or referred to as Clark I) and diphenylarsine cyanide (DC or Clark II), sternutator agents, sneezing gases able to cause bronchial irritation. Cytotoxicity levels and cellular uptake were compared to those of inorganic species: sodium arsenite, NaAsO2 [As(III)], sodium arsenateNa2HAsO4 [As(V)] and methylated arsenicals such as dimethylarsinic acid (DMA) and methylarsonic acid (MMA). The arsenic uptake was demonstrated in an African Green Monkey kidney cell line, CV-1. Quantification of lactate dehydrogenase activityreleased from damaged/dying cells was then measured via an LDH assay. The purpose of this study is to initially investigate toxicity to cells when exposed to different arsenic containing compounds over different concentrations and time ranges from 3 h to 24 h. Furthermore, exposed cells were then analyzed for different arsenic species by high performance liquid chromatography (HPLC) with inductively coupled plasma mass spectrometry to isolate and speciate arsenic fractions followed by nanoLC electrospray ionization mass spectrometry to analyze the molecular level changes of the arsenic based degradation products in the kidney cells. Metabolic changes to the arsenic species were found, and interestingly, at the lowest uptake levels, cytotoxicities were generally higher for the chemical warfare agent degradation products than the inorganic arsenic species.

From Simple Diols to Carbohydrate Derivatives of Phenylarsonic Acid

A series of spiro-arsoranes bearing a phenyl moiety as the fifth substituent were synthesized applying open-chain, as well as cyclic vicinal diols, as chelating molecules by condensation reactions in aprotic solvents. The products synthesized are the spiro compounds of the general formula PhAs(DiolH(-2))(2) derived from the vicinal diols meso-2,3-butanediol, PhAs(meso-2,3-ButdH(-2))(2) (1), exo-cis-2,3-norbornanediol, PhAs{exo-cis-NobdH(-2)}(2) (2), cis-1,2-cyclopentanediol, PhAs(cis-1,2-CptdH(-2))(2) (3), anhydroerythritol, PhAs(AnErytH(-2))(2) (4), cis-1,2-cyclohexanediol, PhAs(cis-1,2-ChxdH(-2))(2) (5), and rac-trans-1,2-cyclohexanediol, rac-{PhAs(trans-1,2-ChxdH(-2))(2)} (6) which were identified as mononuclear compounds. A novel dimeric double-spiro environment for oxyarsoranes was found in the reaction products derived from the sterically demanding diols 1,1'-bicyclohexyl-1,1'-diol {PhAs(BhxdH(-2))O}(2) (7) and perfluorpinacol, {PhAs(FpinH(-2))O}(2) (8). The stability of the compounds in acidic and neutral aqueous media in the presence of organic co-solvents was investigated. A convenient synthetic procedure for spiro-oxyarsoranes, applying water as the solvent, was developed and proven to be advantageous. All of the compounds synthesized in this study were characterized by means of melting-point measurement, single-crystal X-ray analysis, NMR, IR, Raman, UV/vis, and mass spectrometry. The principles found for these reactions were valid for the methyl glycosides of beta-D-ribofuranose and alpha-D-mannopyranose. The spiro-arsorane derived from methyl alpha-D-mannopyranoside, PhAs(Me-alpha-D-Manp2,3H(-2))(2) (9), is the first example of a structurally characterized carbohydrate-arsenic(V) compound.

Separation of Organoarsenicals by Means of Zwitterionic Hydrophilic Interaction Chromatography (ZIC®‐HILIC) and Parallel ICP‐MS/ESI‐MS Detection

AbstractAn analytical scheme was developed for the separation and detection of organoarsenicals using a zwitterionic stationary phase of hydrophilic interaction chromatography (ZIC®‐HILIC) coupled in parallel to electrospray ionization mass spectrometry (ESI‐MS) and to inductively coupled plasma mass spectroscopy (ICP‐MS). The optimization of separation and detection for organoarsenicals was mainly focused on the influence of the percentage of acetonitrile (MeCN) used as a major component of the mobile phase. Isocratic and gradient elution was applied by varying the MeCN percentage from 78 % to 70 % MeCN and 22 % to 30 % of an aqueous solution of ammonium acetate (125 mM NH4Ac; pH 8.3) on a ZIC®‐HILIC column (150 × 2.1 mm id, 3.5 μm), to allow for the separation and successful detection of nine organoarsenicals (i.e., 3‐nitro‐4‐hydroxyphenylarsonic acid (roxarsone, Rox), phenylarsonic acid (PAA), p‐arsanilic acid (p‐ASA), phenylarsine oxide (PAO), dimethylarsinate (DMA), methylarsonate (MMA), arsenobetaine (AsB), arsenocholine (AsC) and trimethylarsine oxide (TMAO)) within 45 min. All analytes were prepared in the mobile phase. The flow rate of the mobile phase, the splitting ratio between ICP‐MS and ESI‐MS detection, and the oxygen addition were adapted to ensure that there appeared a stably burning inductively coupled plasma. Furthermore, the analytical method was evaluated by the identification and quantification of AsB in the reference material DORM‐2 (dogfish muscle) resulting in a 95‐% recovery with respect to the AsB concentration in the extract.

Carbonic anhydrase inhibitors. Cloning, characterization and inhibition studies of the cytosolic isozyme III with anions

The cytosolic human carbonic anhydrase (hCA, EC 4.2.1.1) isozyme III (hCA III) has been cloned and purified by the GST-fusion protein method. Recombinant pure hCA III had the following kinetic parameters for the CO2 hydration reaction at 20°C and pH 7.5: kcat of 1.3 × 104 s− 1 and kcat/KM of 2.5.105 M− 1 s− 1. The first detailed inhibition study of this enzyme with anions is reported. Inhibition data of the cytosolic isozymes hCA I - hCA III with a large number of anions (halides, pseudohalides, bicarbonate, carbonate, nitrate, nitrite, hydrosulfide, sulfate, sulfamic acid, sulfamide, etc.), were determined and these values are comparatively discussed for these three cytosolic isoforms. Fluoride, nitrate, nitrite, phenylboronic acid and phenylarsonic acid (as anions) were weak hCA III inhibitors (KIs of 21–78.5 mM), whereas bicarbonate, chloride, bromide, sulfate and several other simple anions showed KIs around 1 mM. The best hCA III inhibitors were carbonate, cyanide, thiocyanate, azide and hydrogensulfide, which showed KIs in the range of 10–90 μM. It is difficult to explain the inhibitory activity of carbonate (KI of 10 μM) against hCA III, also considering the fact that this ion has an affinity of 15–73 mM for hCA I and II and is in equilibrium with one of the substrates of this enzyme, i.e., bicarbonate, which is a much weaker inhibitor (KI of 0.74 mM against hCA III, of 12 mM against hCA I and of 85 mM against hCA II).

Analysis of accumulation, extractability, and metabolization of five different phenylarsenic compounds in plants by ion chromatography with mass spectrometric detection and by atomic emission spectroscopy

Phenylated arsenic compounds occur as highly toxic contaminants in former military areas where they were formed as degradation products of chemical warfare agents. Some phenylarsenic compounds such as roxarsone and aminophenylarsonic acids were applied as food additive and veterinary drugs in stock-breeding and therefore pose an environmental risk in agricultural used sites. Very few data exist in the literature concerning uptake and effects of phenylarsenic compounds in plants growing on contaminated soils. In this study, the accumulation, extractability, and metabolization of five different phenylarsenic compounds, phenylarsonic acid, p- and o-aminophenylarsonic acid, phenylarsine oxide, and 3-nitro-4-hydroxyphenylarsonic acid called roxarsone, by the terrestrial plant Tropaeolum majus were investigated. Ion chromatography coupled to inductively coupled plasma mass spectrometry was used to differentiate these arsenic compounds, and inductively coupled plasma atomic emission spectroscopy was used for total arsenic quantification. All compounds considered were taken up by the roots and transferred to stalks, leaves, and flowers. The strongest accumulation was observed for unsubstituted phenylarsonic acid followed by its trivalent analogue phenylarsine oxide that was mostly oxidized in soil whereas the amino- or nitro- and hydroxy-substituted phenylarsonic acids were accumulated to a smaller degree. The highest extraction yield of 90% for ground leaf material was achieved by 0.1 M phosphate buffer, pH 7.7, in a two-step extraction with a total extraction time of 24 h. The extraction of higher amounts of arsenic (50–70% of total arsenic present in leaves depending on arsenic species application) from non-ground intact leaves with deionized water in comparison with the buffer (20–40% of total arsenic) is ascribed to osmotic effects. The arsenic species analysis revealed a cleavage of the amino groups from the phenyl ring for plants treated with aminophenylarsonic acids. A further important metabolic effect consisted in the production of inorganic arsenate and arsenite from the phenylated arsonic acid groups.

Carbonic anhydrase inhibitors: Inhibition of the β-class enzymes from the fungal pathogens Candida albicans and Cryptococcus neoformans with simple anions

The catalytic activity and inhibition of the β-carbonic anhydrases (CAs, EC 4.2.1.1) from the pathogenic fungi Candida albicans (Nce103) and Cryptococcus neoformans (Can2) with inorganic anions such as halogenides, pseudohalogenides, bicarbonate, carbonate, nitrate, nitrite, hydrogen sulfide, bisulfite, perchlorate, sulfate were investigated. The two enzymes showed appreciable CO 2 hydrase activity ( k cat in the range of (3.9–8.0) × 10 5 s −1, and k cat/ K m in the range of (4.3–9.7) × 10 7 M −1 s −1). Can2 was weakly inhibited by cyanide and sulfamic acid ( K Is of 8.22–13.56 mM), while all other anions displayed more potent inhibition. Nce103 was strongly inhibited by cyanide and carbonate ( K Is of 10–11 μM), and weakly inhibited by sulfate, phenylboronic, and phenyl arsonic acid ( K Is of 14.15–30.85 mM). These data demonstrate that pathogenic, fungal β-CAs may be targets for the development of antifungals that have a novel mechanism of action.

Arsenic Speciation in Rice and Soil Containing Related Compounds of Chemical Warfare Agents

Diphenylarsinic acid, phenylarsonic acid, methylphenylarsinic acid (MPAA), dimethylphenylarsine oxide (DMPAO), and methyldiphenylarsine oxide (MDPAO) in soil and rice were extracted, separated by reversed-phase chromatography, and quantified by ICPMS with a membrane desolvating system. For the extraction of arsenicals from rice grain and straw, 68% HNO3 provided better extraction efficiency than water, 50% methanol, or 2.0 mol L(-1) trifluoroacetic acid. For the extraction from soil, 68% HNO3 provided better extraction efficiency than H2O, 1 mol L(-1) H3PO4, or 1 mol L(-1) NaOH. The contaminated soil contained all five aromatic arsenicals along with inorganic arsenicals as main species (5.86 +/- 0.19 microg of As kg(-1): 60.8 +/- 2.0% of total extracted As). After pot experiments, rice straw contained mainly DMPAO (7.71 +/- 0.48 microg of As kg(-1): 60.5 +/- 3.7%), MDPAO (0.91 +/- 0.07 microg of As kg(-1): 7.2 +/- 0.5%), and inorganic As (2.85 +/- 0.20 microg of As kg(-1): 22.3 +/- 1.6%). On the other hand, rice grain contained mainly MPAA (1.17 +/- 0.04 microg of As kg(-1): 86.7 +/- 2.7%). The root uptake of each species from the soil and transport from straw to grains were significantly related to the calculated log K(ow) values.

Substituted phenylarsonic acids; structures and spectroscopy

Full NMR and ESI-MS spectra, and differential scanning calorimeter data are presented for 15 substituted phenylarsonic acids, including two new fluoro-substituted examples. X-ray crystal structure determinations of five examples (phenylarsonic acid and the 4-fluoro-, 4-fluoro-3-nitro-, 3-amino-4-hydroxy- and 3-amino-4-methoxy-substituted derivatives) were determined and the H-bonding crystal-packing patterns analysed.