Effect of the specific activity of the tracer on rat luteinizing hormone radioimmunoassay

Rat luteinizing hormone /LH/ was labelled with¹²⁵I by the Chloramine T method.¹²⁵I-LH, used as tracer in radioimmunoassay, was separated from the labelling reaction mixture by gel filtration. By using the proper protein/radioiodine ratio in the labelling reaction mixture the specific activity of¹²⁵I-LH was adjusted to 2.5–20.5 MBq g^–1. The influence of the specific activity on the assay parameters as well as on the tracer stability was investigated.     

Gaussian basis sets for calculation of spin densities in first-row atoms

Summary The suitability of Gaussian basis sets for ab initio calculation of Fermi contact spin densities is established by application to the prototype first-row atoms B-F having open shell p electrons. Small multiconfiguration self-consistent-field wave functions are used to describe relevant spin and orbital polarization effects. Basis sets are evaluated by comparing the results to highly precise numerical grid calculations previously carried out with the same wave function models. It is found that modest contracted Gaussian basis sets developed primarily for Hartree-Fock calculations can give semiquantitative results if augmented by diffuse functions and if further uncontracted in the outer core-inner valence region.     

Resolution of benzo[a]pyrene in complex mixtures of other polycyclic aromatic hydrocarbons. Comparison of two spectrofluorimetric methods applied to water samples

Two spectrofluorimetric methods, second-derivative constant-energy synchronous luminescence (SDCESL) and constant-wavelength synchronous luminescence (CWSL) in combination with multiple linear regression (MLR), for the quantification of benzo[a]pyrene (BaP) at sub-ng mL-1 levels, in the presence of benzo[b]fluoranthene (BbFt), benzo[k]fluoranthene (BkFt), benzo[ghi]perylene (BghiP) and indeno[1,2,3-cd]pyrene (IP), were developed and compared in detail. SDCESL presents lower limits of detection and quantification than CWSL/MLR and also gives more exact and precise results for levels close to the quantification limit. For BaP, SDCESL achieved quantification limits of 0.019 ng mL-1 in river waters and 0.007 ng mL-1 in drinking waters. This work offers a sensitive, precise, accurate, rapid, simple and economic methodology for monitoring BaP in waters for public consumption, meeting all the requirements of the EC Directive 98/83/CE that fixes the maximum admissible limit for this polycyclic aromatic hydrocarbon in drinking waters at of 0.010 ng mL-1.     

Selectivity assessment of a sequential extraction procedure for metal mobility characterization using model phases

This study considers the selectivity of the extractants used in a sequential extraction scheme for metals mobility assessment by analyzing individual mineral phases previously coprecipitated or sorbed with trace metals. The scheme evaluated was a modification of the Tessier et al. [A. Tessier, P.G.C. Campbell, M. Bisson, Anal. Chem. 51 (1979) 844] sequential procedure proposed by the authors. The phases studied were calcite, amorphous iron oxide, hausmannite, humic acid, kaolinite and illite. Selective extractions were obtained for As, Cr, Cu, Ni, Pb and Zn in metal-coprecipitated phases whereas NH(2)OH-HCl was not selective for the extraction of Hg and Cd coprecipitated in hausmannite and amorphous iron oxide, respectively. Otherwise, Cd, Hg, Ni and Zn sorbed on the different phases were released with MgCl(2) and NaOAc/HOAc, but stronger reagents were needed to release As, Cr, Cu and Pb.     

Possible Mechanisms of Intercalation

Recent knowledge of the kinetics and intercalation mechanisms are summarized and accompanied by examples of intercalation reactions of water and ethanol into anhydrous vanadyl phosphate and redox intercalation of alkali metal cations into vanadyl phosphate dihydrate. Three possible mechanisms of intercalation are presented which are based on: (i) a concept of exfoliation of layers; (ii) the formation of stages and randomly stacked layers; (iii) co-existence of intercalated and non-intercalated parts of crystals of the host separated by an advancing phase boundary. The corresponding kinetic curves are ascribed to mechanisms (ii) and (iii).     

Kinetic fluorimetric determination of nanogram amounts of manganese, based on its catalysis of the oxidation of 2-hydroxybenzaldehyde thiosemicarbazone with hydrogen peroxide

A kinetic method is described for the determination of trace amounts of manganese(II), based on its catalytic effect on the oxidation of 2-hydroxybenzaldehyde thiosemicarbazone by hydrogen peroxide. The reaction is followed by measuring the rate of change of fluorescence (lambda(ex) 365 and lambda(em) 440 nm). The calibration is linear over the manganese range 2-9 ng ml with a precision of +/-1%. The proposed method suffers from few interferences.     

Rh(III), Pd(II), Pt(IV) and Au(III) complexes of 2-thiopyrimidine derivatives

Some news thiopyrimidine derivatives and complexes [4-amino-5-nitroso-6-oxo-1,2,3,6-tetrahydro-2-thio-pyrimidine (TANH), its 2-methylthio derivative (MTH), the ammonium salt ofTANH (sTANH) and six new complexes of formulas: Rh(MT)₂Cl · 2H₂O, Pd(MTH)₂Cl₂, Pt(MTH)₂Cl₄, Au(MTH)Cl₃ Pd(TANH)₂Cl₂ and Au(TAN ^–)Cl] have been synthesized and characterized by elemental analysis, IR and¹H-NMR spectroscopy techniques. The thermal behaviour of all compounds has also been studied.

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Rh(III), Pd(II), Pt(IV) und Au(III) Komplexe von 2-Thiopyrimidin Derivaten

Zusammenfassung Es wurden einige neue Thiopyrimidinderivate und deren Komplexe synthetisiert und mittels Elementaranalyse, IR und¹H-NMR charakterisiert: 4-Amino-5-nitroso-6-oxo-1,2,3,6-tetrahydro-2-thio-pyrimidin (TANH), dessen 2-Methylthio-Derivat (MTH), das Ammoniumsalz vonTANH (sTANH) und sechs neue Komplexe der Formeln Rh(MT)₂Cl · 2H₂O, Pd(MTH)₂Cl₂, Pt(MTH)₂Cl₄, Au(MTH)Cl₃, Pd(TANH)₂Cl₂ und Au(TAN ^–)Cl. Das thermische Verhalten der Verbindungen wurde ebenfalls untersucht.

     

Study of zinc thiocarbamide chloride,a single-source precursor for zinc sulfide thin films by spray pyrolysis

Thermal decomposition of the title compound, Zn(tu)₂Cl₂ (tu=thiourea), was studied up to 1200°C in dynamic inert (N₂) and oxidative (air) atmospheres using simultaneous TG/DTA techniques. In addition, XRD and IR were employed ex situ to resolve the reaction mechanism and products. Cubic ZnS (sphalerite) is formed below 300°C in both atmospheres and is observed until 760°C, whereafter it transforms in nitrogen to the hexagonal ZnS (wurtzite). EGA by FTIR revealed the complexity of the decomposition reactions involving also the evolution of H₂NCN, which reacts to form hexagonal ZnCN₂ as revealed by an XRD analysis. This revised version was published online in July 2006 with corrections to the Cover Date.     

Selective extraction of astaxanthin from crustaceans by use of supercritical carbon dioxide

An on-line supercritical fluid extraction (SFE) system coupled to a continuous flow manifold including a UV detector was used as a screening system to extract astaxanthin from crayfish, which was found to be the major carotenoid present in the samples. This compound constitutes the principal additive used to dye salmon flesh. The flow manifold was used to confirm the presence of astaxanthin in the crustacean samples. Also, an HPLC/UV-vis method was used to ascertain that this compound was the major carotenoid extracted under the optimum SFE conditions employed. The influence of SFE operating variables such as pressure, temperature, equilibration time, extraction time, trap temperature, and volume of CO₂ modifier was examined in order to maximize the efficiency of analyte extraction. The use of supercritical CO₂ enables the expeditious, selective, quantitative extraction of astaxanthin from crustaceans.     

Mass spectrometric analysis of porcine rhodopsin

Rhodopsin is the dim light photosensitive pigment of animals. In this work, we undertook to study the structure of rhodopsin from swine and compare it with bovine and rat rhodopsin. Porcine rhodopsin was analyzed using methodology developed previously for mass spectrometric analysis of integral membrane proteins. Combining efficient protein cleavage and high performance liquid chromatography separation with the sensitivity of mass spectrometry (MS), this technique allows the observation of the full protein map and the posttranslational modifications of the protein in a single experiment. The rhodopsin protein from a single porcine eye was sequenced completely, with the exception of two single-amino acid fragments and one two-amino acid fragment, and the gene sequence reported previously was confirmed. The posttranslational modifications, similar to the ones reported previously for bovine and rat rhodopsin, were also identified. Although porcine rhodopsin has a high degree of homology to bovine and rat rhodopsins and most of their posttranslational modifications are identical, the glycosylation and phosphorylation patterns observed were different. These results show that rhodopsin from a single porcine eye can be characterized completely by MS. This technology opens the possibility of rhodopsin structural and functional studies aided by powerful mass spectrometric analysis, using the fellow eye as an internal control.