Characterisation and optimisation of an immunoprobe for triazines

The characterisation and optimisation of an optical immunoassay with label free detection based on Reflectometric Interference Spectroscopy (RIfS) is presented. The immunoprobe is operated in a sequential scheme, where Fab-fragments react with analyte molecules in a first step. In a second step the optical transducer is used to quantify the amount of unoccupied Fab- fragments in the reaction mixture binding to the hapten-modified transducer surface. For optimisation of the test, the Fab-fragment concentration was varied between 2x10(-8) mol/l and 2.5x 10(-9) mol/l. Down to a concentration of 5x10(-9) mol/l a reduction in the limit of detection has been observed. At the lowest concentration investigated no further improvement has been found due to a reduced binding of the analyte and a strong decrease of antibody binding at the transducer surface. This finding could be explained by the thermodynamics of the antigen-antibody reaction and the performance of the optical transducer used. The limit of detection obtained is discussed with respect to thermodynamics, transducer characteristics and immunoprobe test format.     

HPLC separation and quantification of anionic surfactants using an automated on-line ion pair extraction system

Summary Aliphatic anionic surfactants, like alkylsulfonates, alkyl sulfates, -sulfo alkanoic acids and their esters, were separated with respect to their alkyl chain length by high performance liquid chromatography (HPLC) using reversed phase (RP) columns. For sensitive and specific detection of these classes of compounds the HPLC separation was combined with a post-column ion-pair extraction system. The limit of detection is in the range of 3–30 ng. Previously reported detection systems of this kind were modified by changing the inner set-up of the phase separator and the extraction capillary and integrating a purge function, which led to a higher system stability and made automatization possible. In order to optimize the experimental set-up, the influence of the reagent concentration as well as different sizes and materials of the extraction capillary were evaluated. The calibration curve of surfactant concentrations versus fluorescence emission is discussed for sodium decylsulfonate. Since both the electrolyte concentration and the percentage of organic solvents in the mobile phase may adversely affect the detection system, different eluent compositions were tested.This article is part of the planned dissertation of Markus Schoester at the Mathematical Natural Science Faculty of the University of Düsseldorf     

Synthese und Kristallstruktur von Hydronium-tris-ethylendiamin-cobalt(rhodium)-μ-trichloro-nonachlorotrirhenat(II)-chlorid,H3O[MEn3][Re3Cl12]Cl (M=Co,Rh)

Synthesis and Crystal Structure of Hydronium-tris-ethylenediamine-cobalt(rhodium)-μ-trichloro-nonachlorotrirhenate(III)-chloride, H₃O[MEn₃][Re₃Cl₁₂]Cl (M=Co, Rh) The chlorides H₃O[MEn₃][Re₃Cl₁₂]CI (M = Co, 1 ; Rh, 2 ) crystallize from hydrochloric acid solutions of ReCl₃ and MEn₃ · 3H₂O as deep red hexagonal columns. They are isotypic and crystallize with the hexagonal system (P6 , Z = 1; 1: a = 1010.87(3); c = 794.30(4) pm, R = 0.023, R_w = 0.016; 2: a = 1018.58(3); c = 794.74(4) pm, R = 0.026, R_w = 0.018). The anions [Re₃Cl₁₂]^3? are connected via H₃O₊ cation (C.N. 3). The large channels that run in the [001] direction contain, alternatively, the cations [MEn₃]³⁺ and the lonesome Cl^?-anions     

The Monohydrate of Basic Mercuric Nitrate, [Hg(OH)](NO3)(H2O)

Colourless single crystals of [Hg(OH)](NO₃)(H₂O) were obtained by slow evaporation of an aqueous solution of Hg(NO₃)₂ and Bi(NO₃)₃. The crystal structure (orthorhombic, Pbca, Z = 8, a = 943.2(2), b = 697.6(1), c = 1349.0(2) pm, R₁(all) = 0.0780) contains [Hg(OH)] = …OH–Hg–OH–Hg… zig zag chains (O–Hg–O angle: 168°, Hg–O–Hg angle: 112°, Hg–OH distance: 212 pm) to which one water molecule is attached loosely. The [Hg(OH)](H₂O) chains are connected via bis‐monodentate‐bridging nitrate ions to corrugated layers that are stacked in the [001] direction. Hg²⁺ has an effective 2+2+2(+1) coordination.     

Chemotaxonomic features associated with flavonoids of cannabinoid-free cannabis (Cannabis sativa subsp. sativa L.) in relation to hops (Humulus lupulus L.)

The major flavonoids present in the leaves and flowers of the cannabinoid-free cannabis (Cannabis sativa subsp. sativa L.) cultivars Felina and Futura are orientin (1), vitexin (2), luteolin-7-O-beta-D-glucuronide (3), and apigenin-7-O-beta-D-glucuronide (4), while prenylated flavonoids, to which the potent estrogenicity of hops (Humilus lupulus L.) is associated, are absent. The different composition of flavonoids has chemotaxonomic value.     

A pseudoreceptor modelling study of the varicella-zoster virus and human thymidine kinase binding sites

Summary A representative range of pyrimidine nucleoside analogues that are known to inhibit herpes simplex virus (HSV) replication have been used to construct receptor binding site models for the varicella-zoster virus (VZV), thymidine kinase (TK) and human TK1. Given a set of interacting ligands, superimposed in such a manner as to define a pharmacophore, the pseudoreceptor modelling technique Yak provides a means of building binding site models of macromolecules for which no three-dimensional experimental structures are available. Once the models have been evaluated by their ability to reproduce experimental binding data [Vedani et al., J. Am. Chem. Soc., 117 (1995) 4987], they can be used for predictive purposes. Calculated and experimental values of relative binding affinity are compared. Our models suggest that the substitution of one residue may be sufficient to determine ligand subtype affinity.     

The Radical Anions of N,N′-Dicyanoquinone Diimines,a New Class of Electron Acceptors

The radical anions of 12 N,N′-dicyanoquinone diimines, a new class of electron acceptors, hace been characterized by their hyperfine data with the use of ESR and ENDOR spectroscopy. The largest coupling constant (0.30–0.45 mT), due to the two ¹⁴N nuclei in the exocyclic positions, gives rise to a conspicuous broadening of the peripheral ESR lines by an incomplete averaging of the hyperfine anisotropy. The most plausible interpretation of the experimental results for the radical anions of N,N′-dicyano- 1,4-benzoquinone diimine ( 1 ) and N,N′-Dicyano-9,10-anthraquinone diimine ( 9 ) is in terms of both ‘syn’- and ‘anti’-configurations contributing to the ESR and ENDOR spectra and having equal proton- and ¹⁴N-coupling constants. The π-spin distribution in the radical anions of N,N′-dicyanoquinone diimines is compared with those in the analogous ions of tetracyanoquinodimethanes and quinones.     

LCAO-MO-berechnungen an schwefelhaltigen π-elektronensystemen—XXXIV : Nichtbindende S,S-wechselwirkung in polymethinfarbstoffen

Sulfur-containing polymethine dyes exhibit anomalous chromophoric properties. The vinylene shift of the first two homologues is often considerably larger or smaller than the shift between higher members of the series. Moreover, the absorption wavelengths of non-symmetrical dyes with sulfur-containing groups, as calculated by the mean value rule differ from the experimental data, but not in the predicted manner.This deviation is caused by an interannular no-bond SS-interaction in the monomethine ion. This conclusion is supported by the spectra of appropriately-substituted dyes and is substantiated by theoretical considerations. Starting from the well-known symmetry properties of polymethine MO's the simple PMO-method reproduces correctly the effects of the p_π-type overlap between atomic orbitals of adjacent S atoms at long wavelength absorptions: The SS-interactions lead to a hypsochromic shift in monomethines with (4N + 2)π-electrons (N = 1,2…) and to a bathochromic shift in monomethines with (4N)π-electrons.