The preparation of certified calibration solutions for azaspiracid-1, -2, and -3, potent marine biotoxins found in shellfish

The production and certification of a series of azaspiracid (AZA) calibration solution reference materials is described. Azaspiracids were isolated from contaminated mussels, purified by preparative liquid chromatography and dried under vacuum to the anhydrous form. The purity was assessed by liquid chromatography–mass spectrometry and nuclear magnetic resonance spectroscopy. The final concentration of each AZA in a CD₃OH stock solution was determined by quantitative NMR spectroscopy. This solution was then diluted very accurately in degassed, high purity methanol to a concentration of 1.47?±?0.08 μmol/L for CRM-AZA1, 1.52?±?0.05 μmol/L for CRM-AZA2, and 1.37?±?0.13 μmol/L for CRM-AZA3. Aliquots were dispensed into argon-filled glass ampoules, which were immediately flame-sealed. The calibration solutions are suitable for method development, method validation, calibration of liquid chromatography or mass spectrometry instrumentation and quality control of shellfish monitoring programs.     

Biosynthesis of 13-desmethyl spirolide C by the dinoflagellate Alexandrium ostenfeldii

Biosynthetic origins of the cyclic imine toxin 13-desmethyl spirolide C were determined by supplementing cultures of the toxigenic dinoflagellate Alexandrium ostenfeldii with stable isotope-labeled precursors [1,2-13C2]acetate, [1-13C]acetate, [2-13CD3]acetate, and [1,2-13C2,15N]glycine and measuring the incorporation patterns by 13C NMR spectroscopy. Despite partial scrambling of the acetate labels, the results show that most carbons of the macrocycle are polyketide-derived and that glycine is incorporated as an intact unit into the cyclic imine moiety. This work represents the first conclusive evidence that such cyclic imine toxins are polyketides and provides support for biosynthetic pathways previously defined for other polyether dinoflagellate toxins.     

A higher yielding route to octasilsesquioxane cages using tetrabutylammonium fluoride, Part 2: further synthetic advances, mechanistic investigations and X-ray crystal structure studies into the factors that determine cage geometry in the solid state

The recently-reported reaction of triethoxysilanes with tetrabutylammonium fluoride in the presence of scarce water provides a higher yielding route to substituted octasilsesquioxane cages. Further cages have now been prepared in good yield using this route and their X-ray crystal structures demonstrate that their cage geometries in the solid state are very similar with the packing constraints of the crystal lattices appearing to have the greatest influence on the geometry of the cage core. The mechanism of the reaction has been examined and the proposed mechanism of cage formation validated, though its exclusivity has not been categorically proven. By careful choice of reaction conditions, dramatic increases in rate and yield have been demonstrated.     

Polycyclic aromatic hydrocarbons as universal bases in peptide nucleic acid

Polycyclic aromatic hydrocarbons were found to be promising universal bases in PNA·DNA double helices. Several of the arenes paired promiscuously with any of the four canonical bases. However, the stabilities of the duplexes depended on the size and shape of the arene.     

Measurement of 3-hydroxyisovaleric acid in urine from marginally biotin-deficient humans by UPLC-MS/MS

Measurement of 3-hydroxyisovaleric acid (3HIA) in human urine has been shown to be a useful indicator of biotin status for a variety of clinical situations, including pregnancy. The work described herein presents a novel UPLC-MS/MS method for accurate and precise quantitation of urinary 3HIA. This method utilizes sample preparation prior to quantitation that has been simplified compared to the previous GC-MS method. To demonstrate the suitability of the UPLC-MS/MS method for human bio-monitoring, this method was used to measure 3-HIA in 64 human urine samples from eight healthy adults in whom marginal biotin deficiency had been induced experimentally by egg white feeding. 3HIA was detected in all specimens; the mean concentration [±standard deviation (SD)] was 80.6 ± 51 μM prior to inducing biotin deficiency. Mean excretion rate for 3HIA (expressed per mol urinary creatinine) before beginning the biotin-deficient diet was 8.5 ± 3.2 mmol 3HIA per mol creatinine and the mean increased threefold with deficiency. These specimens had been previously analyzed by GC-MS; the two data sets showed strong linear relationship with a correlation coefficient of 0.97. These results provide evidence that this method is suitable for bio-monitoring of biotin status in larger populations.     

High-intensity lasers and controlled fusion

The use of high-intensity lasers to cause ignition in inertial confinement fusion is presented, with emphasis on current experimental programs and physical concepts that are at the forefront of the field. In particular, we highlight the issues of fast electron transport through dense materials, an essential element of the Fast Ignitor concept.Received: 22 November 2002, Published online: 5 August 2003PACS: 52.20.Fs Electron collisions - 52.38.Kd Laser-plasma acceleration of electrons and ions     

Poly(aryl ether)s containing o‐terphenyl subunits. III. Random copoly(ether imide)s

The synthesis of a new diamine monomer, N‐n‐butyl 3,12‐diamino‐5,6,9,10‐tetrahydro[5]helicene‐7,8‐dicarboxylic imide (4), that contains a helically locked, U‐shaped 4′,4″‐o‐terphenyl moiety is described. The monomer was polymerized with 3,3′,4,4′‐oxydiphthalic dianhydride and 2,2‐bis[4‐(4‐aminophenoxy)phenyl]propane to form a series of copoly(ether imide)s (5a–e). The incorporation of 4 into the poly(ether imide)s varied the glass‐transition temperature of the copolymers of which it was a part. There was a tendency to form macrocyclic materials at higher molar percentages of 4 during polymerization. The fluorescence of all the copoly(ether imide)s gradually decreased as the content derived from monomer 4 increased in the polymer. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 758–763, 2000     

Measuring naphthenic acids concentrations in aqueous environmental samples by liquid chromatography

Naphthenic acids are found in wastewaters from petroleum refineries and oil sands extraction plants. Currently, the concentrations of these toxic carboxylic acids are determined by extracting them into methylene chloride and measuring the absorption of the carboxyl group by Fourier-transform infrared (FTIR) spectroscopy. An improved HPLC method, that is simpler and faster than the FTIR method, was used to detect the 2-nitrophenylhydrazides of the naphthenic acids at concentrations as low as 5 mg l(-1). Analyses of 58 oil sands water samples showed that the naphthenic acids concentrations determined by FTIR were on average 11% higher than those determined by HPLC.