New approach to quantitative analysis of benzo[a]pyrene in food supplements by an immunochemical column test

A quantitative immunochemical rapid test for sensitive determination of benzo[a]pyrene (BAP) as a model analyte was developed making use of a handheld reader for results evaluation. The covalent immobilization of antibodies to different Sepharose gels, i.e., CNBr-activated Sepharose 4B and CNBr-activated Sepharose 4 Fast Flow was compared with adsorption to a polyethylene support. The lowest limits of detection (LOD) were 4 ng L⁻¹ and 40 ng L⁻¹, respectively, using optimized assay conditions. The developed test was applied to food supplements (garlic, black radish and maca), including a pretreatment procedure. LOD of 9 ng kg⁻¹ and linear range of 13-80 ng kg⁻¹ were obtained. Results of BAP determination in naturally contaminated samples were confirmed by high-performance liquid chromatography coupled to fluorescence detection and a good correlation was achieved. We suggest that the developed test format can be used to quantitative detection of the low molecular weight analytes, such as mycotoxins, pesticides, other pollutants in food and environmental samples.     

Regenerable immuno-biochip for screening ochratoxin A in green coffee extract using an automated microarray chip reader with chemiluminescence detection

Ochratoxin A (OTA) can contaminate foodstuffs in the ppb to ppm range and once formed, it is difficult to remove. Because of its toxicity and potential risks to human health, the need exists for rapid, efficient detection methods that comply with legal maximum residual limits. In this work we have synthesized an OTA conjugate functionalized with a water-soluble peptide for covalent immobilization on a glass biochip by means of contact spotting. The chip was used for OTA determination with an indirect competitive immunoassay format with flow-through reagent addition and chemiluminescence detection, carried out with the stand-alone automated Munich Chip Reader 3 (MCR 3) platform. A buffer model and real green coffee extracts were used for this purpose. At the present, covalent conjugate immobilization allowed for at least 20 assay-regeneration cycles of the biochip surface. The total analysis time for a single sample, including measurement and surface regeneration, was 12 min and the LOQ of OTA in green coffee extract was 0.3 μg L⁻¹ which corresponds to 7 μg kg⁻¹.     

Cuprous complexes and dioxygen. IX. Formation of a unique trimeric species Cu3L and Ligand Oxidation (L  cis,cis-1, 3, 5-cyclohexanetriamine)

The complexation of Cu⁺ by the potentially tripod like ligand cis, cis-1, 3, 5 cyclohexanetriamine (chta) has been studied potentiometrically in aqueous acetonitrile (an). The expected tetracoordinated species Cu (chta) ? (an)⁺ was formed only at rather high pH with log K (Cu (an)⁺ + chta ? Cu (chta) · (an)⁺) = 6.94. Quite unexpectedly the most stable complex in neutral solution was the trimetric species Cu³ (chta) with log K (3 Cu⁺ + 2 chta ? Cu³ (chta)) = 31.75. In addition, the ternary complexes Cu (LH²) · (an)³⁺ and Cu (LH) · (an)²⁺ (L = chta) are formed at low pH. From model considerations, Cu³ (chta) must contain two ligand molecules with all amino groups in equatorial position, linked by three linearly coordinated Cu⁺-ions. Cu₃ (chta)³⁺₂ shows no measurable reactivity towards dioxygen. At pH values above 9, very rapid O₂-uptake due to Cu (chta) · (an)⁺ is observed. In this reaction, Cu⁺-autoxidation is stoichiometrically coupled to ligand oxidation, followed by a much slower Cu-catalyzed secondary reaction of the primary oxidation product of chta. Hydrogen peroxide and likely also superoxide, are involved in the coupled Cu⁺/ligand oxidation.     

Logarithmic vector-valued modular forms and polynomial-growth estimates of their Fourier coefficients

We establish (Theorem?3.6) polynomial-growth estimates for the Fourier coefficients of holomorphic logarithmic vector-valued modular forms.     

Nörlund-Verfahren für Funktionen

Ohne ZusammenfassungDem Andenken anIssai Schur gewidmet.This research was supported by the United States Air Force through the Office of Scientific Research, of the Air Research and Development Command, under Contract Number AF 18 (600)–691.     

Md-simulation of α-keratin intermediate filaments

In recent years powerful computer systems have become readily accessible to simulate complex chemical problems. Based on the primary structure of the intermediate filament monomer unit of wool, small sequences are selected. Their molecular dynamic behaviour is simulated, in order to investigate the secondary and tertiary structure as well as their stability. The simulations are carried out for a helical segment and a linker segment, selecting the ideal α-helix as start conformation. In vacuum all simulations show an unstable α-helix due to shifts of the intrahelical hydrogen bonds. So a new helical structure with a larger helix diameter is formed. However in simulations with surrounding water the α-helix remains stable throughout the simulation time. Up to now it has not been possible to dectect any fundamental difference in the molecular dynamic behaviour of the helical and the linker segment.     

Modeling of the transition temperature for the helical denaturation of α-keratin intermediate filaments

Simulations of the stability of the secondary and tertiary structure of the α-keratin intermediate filament (IF) monomeric unit of wool are reported. Based on the assumed secondary structure three segments of the primary structure were selected: 1A, L12, and a part of 2B. Starting with an ideal α-helical conformation for each IF-segment, molecular dynamics simulations were carried out on the atomistic level at various temperatures in vaccum using the CFF91 force field. In either simulation the expected destabilization of the helical structure with increasing simulation temperature was observed. By use of different procedures of analysis, transition temperatures for the α-helical denaturation were determined that are significantly higher for the supposedly α-helical segments 1A and 2B than for the linker segment L12. The different stabilities of segments 1A and L12 were further verified through simulations in water environment that show the linker segment to be non-helical at room temperature. The lower transition temperature of segment L12 confirms the expectation that its amino acid sequence leads to increased conformational flexibility. The mobility of the water molecules surrounding the IF-segment is found to be significantly decreased by protein/water interactions.