Validation of a screening method for corticosteroids in doping analysis by liquid chromatography/tandem mass spectrometry

A selective and sensitive method for the screening of nine corticosteroids in human urine has been validated. Analyses were performed using an ion trap instrument equipped with an electrospray ionisation (ESI) interface. All corticosteroids were separated in less than 20 min after liquid/liquid extraction with diethyl ether. The limit of detection for all substances was 4 ng/mL or lower. The method was applied to detect betamethasone after the intramuscular injection of Diprophos. Betamethasone could be detected for up to 12 days after administration. Validation of the chromatographic separation and mass spectrometric identification of mixtures of betamethasone and dexamethasone are also presented.     

An efficient synthesis of 6-formyl-1,2-dihydro-2-oxo-3-pyridinecarboxylic acid and some carbonyl derivatives of it and its 6-acetyl homologue

Starting with 1,1-dimethoxy-2-propanone ( 1 ), 6-formyl-1,2-dihydro-2-oxo-3-pyridinecarboxylic acid ( 5a ) has been prepared in large quantities by a highly efficient, 4-step synthesis. This compound, along with its one carbon homologue, 6-acetyl-1,2-dihydro-2-oxo-3-pyridinecarboxylic acid ( 5b ) has been reacted with several carbonyl derivative forming reagents to provide a series of side chains for β-lactams. Among these carbonyl derivatives are styrylamides which were prepared from Wittig and Horner-Emmons reagents. The preparation of the phosphonium salts and phosphonate esters is also described.     

REVERSIBLE PHOTOCHEMISTRY IN THE α-SUBUNIT OF PHYCOERYTHROCYANIN: CHARACTERIZATION OF CHROMOPHORE AND PROTEIN BY MOLECULAR DYNAMICS AND QUANTUM CHEMICAL CALCULATIONS

The ground and excited state properties of two regions in the Δ15-configurational space of the phycoviolobilin chromophore in the α-subunit of phycoerythrocyanin are analyzed. Molecular dynamics calculations reveal that the chromophore geometry determines the active-site dynamics. The excited state torsional potential surface shows a negative barrier for isomerization and trapping of an activated complex. Strong coupling of excited states localized in the chromophore and charge transfer states from the surrounding polar residues provides favorable prerequisites for fast excited state surface crossing in competition with other deactivation processes. The formation of a photoreduced intermediate following the photoinduced charge transfer may trigger subsequent chemical reactions.     

Crystal structure of 2-nitropyridine

The crystal structure of 2-nitropyridine has been determined by x-ray diffraction analysis. The influence of the nitro group on the geometric parameters of the molecule was evaluated, as well as its influence on the molecular parameters of other nitropyridines, depending on the position of this group in the pyridine ring. Novosibirsk Institute of Organic Chemistry, Siberian Branch of the Russian Academy of Sciences, Novosibirsk 630090. E-mail: gatilov@nioch.nsc.ru. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1367–1371, October, 1998.     

Determination of naturally occurring radionuclides in ultrapure organic liquids

For the determination of trace elements in organic liquids radiochemical neutron activation analysis has been combined with counting methods geared to various decay modes of indicator radionuclides leading to a high sensitivity required for ultrapure samples. The activation parameters such as irradiation time, sample mass and neutron flux have been enlarged to the maximum possible in the available irradiation facility. Separation yields and adsorption losses have been studied in detail for a set of elements in order to rule out losses during the separation process. The attainable limits of detection are 2 · 10^–16g/g for U and Lu, in the 5 · 10^–15g/g range for Th and Sm, in the 1 · 10^–14g/g region for La, 5 · 10^–13g/g for Rb, Cd and 2 · 10^–12g/g for K and In. Although the analysis focused on traces of naturally occurring radioisotopes, results for Cr, Fe, W and Zn are presented as well.     

The allyloxycarbonyl group for alcohol protection: quantitative removal or transformation into allyl protecting group via π-allyl complexes of palladium

In the presence of Pd catalysts and under mild, essentially nonbasic conditions, the allyloxycarbonyl derivatives of alcohols may be either converted into the corresponding allyl ethers or hydrogenolysed (Bu₃SnH) back to the starting alcohol.     

Non-thermal effects in laser-enchanced etching of silicon by XeF2

Mass spectrometric studies of the products of the reaction of XeF₂ with silicon in the dark and under visible illumination have been carried out. The data show that photo-enchancement of the reaction is substantially different from thermal enchancement. It is proposed that photogenerated charge carries influence strongly both the overall etch rate and the reaction product distribution.     

Neutron activation analysis of heavy rare earths

A method of nondestructive activation analysis of heavy rare earth elements (Sm−Lu) is described. Intensities of γ-ray peaks are compared to that of an internal reference after irradiations by both thermal and fission spectrum neutrons. Results are obtained from computer comparisons of peak areas. Work was performed at the Ames Laboratory of the U.S. Atomic Energy Commission. Contribution No. 2895.     

Immunomagnetic separation of tumor necrosis factor alpha. II. In situ procedure for the human gingival space.

An in situ procedure has been developed for the separation of tumor necrosis factor (TNF) alpha directly from the fluid in the human gingival space. Paramagnetic beads coated with anti-TNF monoclonal antibodies were introduced into the gingival space of the subject with a polypropylene-tipped calibrated delivery system and retrieved using a permanent magnet designed to fit into the space. After retrieval, the amount of immunoadsorbed TNF was quantified using an immunochemical assay called the "cluster assay". The results indicate that following the appropriate preparation of the site, over 95% of the beads could be recovered. With this method we found that 62% of those cavities sampled contained TNF and that the values ranged from 0.10 to 13.0 ng/ml with a mean value of 1.7 ng/ml. A comparison of these values with those obtained from the same space using other methods suggests that the immunomagnetic method was more effective in retrieval of TNF. Because the separation is performed in situ we have named the procedure "chromatobiosis".