The origin of arsenobetaine in marine animals

Trimethyl(carboxymethyl)arsonium zwitterion (arsenobetaine) is virtually ubiquitous in marine animals consumed by man. Experimental work on the transformation of arsenate to arsenobetaine in the marine environment is reviewed. Current evidence favors the conversion of arsenate to dimethyl(ribosyl)arsine oxides by algae, and the microbially mediated transformation of dimethyl(ribosyl)arsine oxides to arsenobetaine or to its immediate precursors in the sediments. Information about the transfer of arsenobetaine from the sediments to marine animals is lacking.     

Metabolism of arsenic compounds by the blue mussel mytilus edulis after accumulation from seawater spiked with arsenic compounds

Blue mussels (Mytilus edulis) were exposed to 100 μg As dm^?3 in the form of arsenite, arsenate, methylarsonic acid, dimethylarsinic acid, arsenobetaine, arsenocholine, trimethylarsine oxide, tetramethylarsonium iodide or dimethyl-(2-hydroxyethyl)arsine oxide in seawater for 10 days. The seawater was renewed and spiked with the arsenic compounds daily. Analyses of water samples taken 24 h after spiking showed that arsenobetaine and arsenocholine had been converted to trimethylarsine oxide, whereas trimethylarsine oxide and tetramethylarsonium iodide were unchanged. Arsenobetaine was accumulated by mussels most efficienty, followed in efficiency by arsenocholine and tetramethylarsonium iodide. None of the other arsenic compounds was significantly accumulated by the mussels. Extraction of mussel tissues with methanol revealed that control mussels contained arsenobetaine, a dimethyl-(5-ribosyl)arsine oxide and an additional arsenic compound, possibly dimethylarsinic acid. Mussels exposed to arsenobetaine contained almost all their experimentally accumulated arsenic as arsenobetaine, and mussels exposed to tetramethylarsonium iodide contained it as the tetramethylarsonium compound. Mussels exposed to arsenocholine had arsenobetaine as the major arsenic compound and glycerylphosphorylarsenocholine as a minor arsenic compound in their tissues. The results show that arsenobetaine and arsenocholine are efficiently accumulated from seawater by blue mussels and that in both cases the accumulated arsenic is present in the tissues as arsenobetaine. Consequently arsenobetaine and/or arsenocholine present at very low concentrations in seawater may be responsible for the presence of arsenobetaine in M. edulis and probably also among other marine animals. The quantity of arsenobetaine accumulated by the mussels decreases with increasing concentrations of betaine. HPLC-ICP-MS was found to be very powerful for the investigation of the metabolism of arsenic compounds in biological systems.     

Negative magnetoresistance in Ba2CoS3

A small negative magnetoresistance and metallic-like behaviour has been detected for the first time in a one-dimensional sulfide containing Co2+.     

Influence of steric and electronic properties of the defect site, lanthanide ionic radii, and solution conditions on the composition of lanthanide(III) alpha1-P2W17O6110- polyoxometalates

This study identifies the principles that govern the formation and stability of Ln complexes of the (alpha(1)-P(2)W(17)O(61))(10-) isomer. The conditional stability constants for the stepwise formation equilibria, K(1cond) and K(2cond), determined by (31)P NMR spectroscopy, show that the high log K(1cond)/log K(2cond) ratio predicts the stabilization of the 1:1 Ln/ (alpha(1)-P(2)W(17)O(61))(10-) species. The value of log K(1cond) increases as the Ln series is traversed, consistent with the high charge/size requirement of the basic alpha(1) defect site. The conditional stability constants, K(2), are very low and are highly dependent on the countercations in the buffer. The source of the instability is understood from the crystal structures of the early-mid lanthanide analogues, where the close contact of the (alpha(1)-P(2)W(17)O(61))(10-) units result in severe steric encumbrance. The electronic properties of the alpha(1) defect along with the lanthanide ionic radii and countercation composition are important parameters that need to be considered for a rational synthesis of lanthanide polyoxometalates.     

Determination of arsenic species: a critical review of methods and applications, 2000-2003

We review recent research in the field of arsenic speciation analysis with the emphasis on significant advances, novel applications and current uncertainties.     

Determination of an arsenosugar in oyster extracts by liquid chromatography-electrospray mass spectrometry and liquid chromatography-ultraviolet photo-oxidation-hydride generation atomic fluorescence spectrometry

HPLC-UV-HG-AFS analysis of aqueous extracts of oysters (Crassostrea gigas) taken from the southwestern Atlantic coast of Spain showed the presence of arsenite, arsenate, dimethylarsinic acid and an unidentified arsenic peak. Subsequent analysis of the oyster samples by LC-electrospray MS and comparison with four standard dimethylarsinoylribosides (arsenosugars), showed that the previously unidentified peak was an arsenosugar (arsenosugar 2). When the arsenosugar in the oyster was quantified using the two detection methods and external calibration with standard arsenosugar, there was a large discrepancy between the two sets of results. The LC-MS analysis was strongly affected by the sample matrix and gave concentrations 50% lower than those obtained by AFS detection. When the method of standard addition was applied to the LC-MS analysis, the results were comparable to the AFS data. The matrix effects were eliminated by subjecting the extract to a clean-up procedure with anion-exchange and gel permeation preparative chromatography before the LC-MS analysis. The arsenosugars gave a small signal without photo-oxidation when they were analysed by HPLC-HG-AFS. Possibly this resulted from partial decomposition of the arsenosugar to dimethylarsinic acid under the acidic conditions employed in the hydride generation step.     

Synthesis of novel 2-substituted-5-oxycoumarans via A direct route to 2,3-dihydro-5-hydroxy-2-benzofuranacetic acids

A number of novel 2-substituted 2,3-dihydro-5-benzofuranols optionally protected on 5-OH group have been prepared via a simple two step route to racemic 2,3-dihydro-5-hydroxy-2-benzofuranacetic acids from hydroquinones and 4-bromocrotonates.     

The DNSev™ expert system in the auto-verification of tumour markers and hormones results

Most of the immunoassays workload is processed in clinical laboratories within a time span comparable to the clinical chemistry and the haematology assays and the analytical work is usually completed between 1:00 and 2:00 p.m. In order to accelerate the auto-verification of the results of tumour markers (Total and free PSA, CEA, CA 125, CA 15-3, CA 19-9, TPA, AFP, NSE, S 100 protein), and hormones (TSH, FT4, FT3, Prolactin, total testosterone) and Procalcitonin (PCT) we used DNSev^TM expert system implementing 13 rules based on decision levels/reference intervals and reference change values. The auto-verification procedure has been implemented after a 6-month trial in June 2004 and in 2005 the immunoassays section supervisor was able to verify about 500 results in about 30 min 5 days/week. We conclude that the auto-verification of immunoassays implemented in our laboratory is fast and consistent among different supervisors and leaves more time for an effective and timely interaction with clinicians and general practitioners.Presented at the 10th Conference Quality in the Spotlight, March 2005, Antwerp, Belgium