Specific detection of Clostridium botulinum types A,B, E,and F using the polymerase chain reaction

Clostridium botulinum organisms generally produce 1 of 4 neurotoxin types (A, B, E, and F) associated with human illness. Neurotoxin type determination is important in identification of the bacterium. A polymerase chain reaction (PCR) method was developed to identify 24 h botulinal cultures as potential types A, B, E, and F neurotoxin producers as well as other clostridial species which also produce neurotoxins. Components of the PCR and amplification conditions were adjusted for optimal amplification of toxin gene target regions to enable simultaneous testing for types A, B, E, and F in separate tubes using a single thermal cycler. Each primer set was specific for its corresponding toxin type. A DNA extraction procedure was also included to remove inhibitory substances that may affect amplification. This procedure is rapid, sensitive, and specific for identification of toxigenic C. botulinum.     

Determination of copper, iron, manganese and zinc in river and estuarine water by atom trapping-flame atomic absorption spectrometry

Summary A simple method is described for the atomic absorption (AA) determination of Cu, Fe, Mn and Zn in river and estuarine water using two atom trapping techniques: a water-cooled dual silica tube and a commercially available double-slotted quartz tube mounted in an air-acetylene flame. Rapid, accurate analyses can be achieved using continuous aspiration. The concentration detection limits were 0.9, 1.5 and 0.3 ng ml^–1 for Cu, Mn and Zn, respectively, using a 2 min in situ preconcentration time with the dual silica tube atom trap and 4.0, 12.1, 2.0 and 1.2 ng ml^–1 for Cu, Fe, Mn and Zn, respectively, using the double-slotted quartz tube. The relative standard deviations are of the order of 2.9–6.9% for both techniques. The accuracy was assessed by analyses of NRCC SLRS-2 riverine and SLEW-1 estuarine water reference materials. Basic performance characteristics are also given for Ag, Bi, Cd, In, Pb and Tl using the dual silica tube atom trap.     

The fallaxidin peptides from the skin secretion of the Eastern Dwarf Tree Frog Litoria fallax. Sequence determination by positive and negative ion electrospray mass spectrometry: antimicrobial activity and cDNA cloning of the fallaxidins

The glandular skin secretion of the Eastern Dwarf Tree Frog Litoria fallax contains nine peptides named fallaxidins. The sequences of these peptides were elucidated using a combination of positive and negative electrospray mass spectrometry together with Edman sequencing. Among these peptides are: (i) fallaxidins 1.1 and 2.1 which have the sequences YFPIPI-NH2 and FWPFM-NH2. The activities of these peptides are unknown, but it has been shown that they are not smooth muscle active, opioids or antimicrobially active, nor do they effect proliferation of lymphocytes; (ii) two weakly active antibiotics, fallaxidins 3.1 and 3.2 (e.g. fallaxidin 3.1, GLLDLAKHVIGIASKL-NH2), and a moderately active antibiotic fallaxidin 4.1 (GLLSFLPKVIGVIGHLIHPPS-OH). Fallaxidin 4.1 has an unusual sequence for an antibiotic, containing three Pro residues together with a C-terminal CO2H group. cDNA cloning has confirmed the identity of the nine isolated peptides from L. fallax, together with five additional peptides not detected in the peptide profile. The pre-regions of the nine preprofallaxidins are conserved and similar to those of the caerin peptides from L. caerulea and L. splendida, suggesting that the fallaxidin and caerin peptides, although significantly different in sequence, originated from a common ancestor gene.     

Variable incidence angle X-ray absorption fine structure spectroscopy: a zirconia film study

Variable incidence angle X-ray absorption fine structure (VIAXAFS) spectroscopy offers a non-destructive ability to investigate film nano-structures. This technique was applied, spanning sample-beam angles from a grazing to normal incidence on a film obtained by zirconia sputtering on flat sample of stainless steel. X-ray absorption fine structure analysis on the Zr K edge identified chemical, defects and fractal structures through the film depth. VIAXAFS revealed occurrence of zirconium monoxide fractions at the surface a reduced state of zirconium oxide vs. the zirconium dioxide bulk. The discussion underlines that the technique may quantify the profile of various sub-layers, nano-pores, dislocations, vacancies or defect features.     

"Tethered" Ru(II) catalysts for asymmetric transfer hydrogenation of ketones

Stereochemically well-defined ruthenium(II) catalysts have been applied to the asymmetric transfer hydrogenation of a series of ketones. In one case, statistical experimental design was employed to optimize the enantiomeric excess of the product. In the case of the TsDPEN-based systems, the replacement of trans-1,2-diphenyl substitution with cis-, or deletion of one of the phenyl groups, results in significant deterioration of the enantiomeric excess. A new method is described for the synthesis of tethered amino alcohol-containing catalysts.     

Synthesis,characterization and photochemistry of some monometallic and bimetallic 2,2′-bipyrimidine complexes of chromium and tungsten carbonyls

Synthesis, electronic absorption spectra, ¹³C NMR and photochemistry are reported for the complexes M(CO)₄bpym (M = Cr or W) and [W(CO)₄]₂bpym. The electronic absorption spectra indicate, for these complexes, that the lowest lying metal-to-ligand (L) charge transfer (MLCT) excited state is lower in energy than the ligand field (LF) excited states. The ¹³C NMR spectra showed that the chemical shifts of C(5) and C(6) for the M-bpym complexes move downfield with respect to that of the free ligand, bpym, while C(4) moves upfield upon complexation. Small, wavelength-dependent quantum yields for loss of CO were obtained upon irradiation. These quantum yields were an order of magnitude larger for the Cr-bpym complex than for the W complexes (Φ = 2.4 x 10^?2 quanta/min for Cr-bpym, 2.5 x 10^?3 quanta/min for W-bpym and 1.1 x 10^?3 quanta/min for W-bpym-W, λ_irr = 366 nm).     

Determination of selected trace metals in scallops by flame atomic absorption spectrometry after removal of sodium on hydrated antimony pentoxide

Hydrated antimony pentoxide is used to remove sodium ion for the determination of trace metals in scallop specimens of Plactopecten magellanicus. The concentrations of Cd, Cr, Co, Cu, Au, Fe, Pb, Mn, Hg, Ni, Ag and Zn were determined in the samples and in a standard reference material. This method yields improved detection limits with simple apparatus.