Displacement immunoassay for the detection of ochratoxin A using ochratoxin B modified glass beads

We report here the development of a new assay for the detection of ochratoxin A (OTA) based on the use of its dechlorinated analogue, ochratoxin B (OTB), in a displacement immunoassay. OTB was immobilised on controlled-pore glass beads followed by the binding of anti-OTA antibody, with anti-IgG antibody peroxidase conjugate used as a label. In this manner, an original bio-sensing material was obtained. Upon incubation of this material with OTA, the toxin competes with OTB for the binding sites of the anti-OTA antibodies and releases the antibody-tagged peroxidase complex into the solution. Compared to classic competitive immunoassays, this newly developed displacement immunoassay presents a similar detection limit and assay time. Moreover, the detection, based on the activity of the horseradish peroxidase, is performed for the first time in situ using wine samples.     

Phosphotriesterase: A complementary tool for the selective detection of two organophosphate insecticides: Chlorpyrifos and chlorfenvinfos

This work shows the possibility of combining the high sensitivity of genetically-modified Drosophila melanogaster acetylcholinesterase (B394) with the ability of phosphotriesterase (PTE) to hydrolyse organophosphate compounds, in the aim of developing a biosensor selective to two insecticides of interest: chlorpyrifos and chlorfenvinfos. The studies clearly demonstrate that chlorfenvinfos is a substrate that acts as competitive inhibitor of PTE, therefore preventing the efficient hydrolysis of other pesticides, including chlorpyrifos. A bi-enzymatic sensor was designed by immobilizing both B394 and PTE in a polyvinylalcohol matrix. The sensor was shown to be able to discriminate between chlorpyrifos and chlorfenvinfos inhibitions.     

Approximative "one particle" bridge function B(1)(r) for the theory of simple fluids

New properties for the one particle bridge function B(1)(r), which are necessary to the calculation of the excess chemical potential betamue), are derived for the hard sphere fluid. The method, which only requires the knowledge of the bridge function B(2)(r), is based on an investigation of the correlation function dependence on the Kirkwood charging parameter. In this framework, the unavoidable question of topological homotopy is addressed. As far as B(2)(r) is considered as exact, this work provides useful information on B(1)(r) in the well identified dynamical regimes of the hard sphere fluid. Signatures of the transitions between these regimes are identified on the trends of B(1)(r). This approach provides self-consistent results for betamue) that agree very well with simulation data.     

Optimization of in-situ monolithic synthesis for immunopreconcentration in capillary

Poly(glycidyl methacrylate-co-ethylene dimethacrylate) monoliths have been synthetized in fused-silica capillary. The monomer mixture composition, initiation mode and porogen composition were optimized in order to provide a monolith with an homogeneous morphology and able to generate an electroosmotic flow via the incorporation of a small percentage of monomers possessing sulfonate group. Anti-ochratoxin A antibodies were immobilized through a single step on the epoxy groups leading to a miniaturized immunoextraction column. In order to evaluate the specificity of the analyte-antigen interaction on this immunosorbent, the retention of ochratoxin A was examined on this support but also on two complementary sorbents: one constituted by the non-bonded monolith and another one bonded with non-specific antibodies. Only the monolith bonded with anti-ochratoxin A antibodies lead to retention, showing the specificity of the interactions involved. This affinity phase based on a monolithic polymer support exhibits a high potential for specific preconcentration of small molecules.     

Expanding the accessible chemical space by solid phase synthesis of bicyclic homodetic peptides

Norbornapeptides (bicyclo[2.2.1]heptapeptides) and related bicyclic homodetic peptides were prepared by solid-phase peptide synthesis using an orthogonal protection scheme. These conformationally rigid peptides cover an almost pristine area of peptide topological space and adopt globular shapes similar to those of short α-helical peptides.     

A Flexible Route to Mannose 6-Phosphonate Functionalized Derivatives

A new approach for the synthesis of a mannose 6-phosphonate isosteric analog of mannose 6-phosphate is reported. The mannosylphosphonate has been prepared in a multistep synthesis involving an homologation reaction of the methyl f - D -mannopyranoside followed by an Arbuzov reaction between a bromohomomannosyl derivative and the tris (trimethylsilyl)phosphite. This approach, avoiding the deprotection of dialkylphosphonate, allowed us to prepare the mannose 6-phosphonate in good yield. The described method was successfully extended to the preparation of a mannose 6-phosphonate linked to a cholesteryl moiety. This strategy affords a more general route for a wide range of functionalized mannose 6-phosphonate derivatives.     

OMA and OPA—Software-Supported Mass Spectra Analysis of Native and Modified Nucleic Acids

The platform-independent software package consisting of the oligonucleotide mass assembler (OMA) and the oligonucleotide peak analyzer (OPA) was created to support the analysis of oligonucleotide mass spectra. It calculates all theoretically possible fragments of a given input sequence and annotates it to an experimental spectrum, thus, saving a large amount of manual processing time. The software performs analysis of precursor and product ion spectra of oligonucleotides and their analogues comprising user-defined modifications of the backbone, the nucleobases, or the sugar moiety, as well as adducts with metal ions or drugs. The ability to expand the library of building blocks and to implement individual structural variations makes it extremely useful for supporting the analysis of therapeutically active compounds. The functionality of the software tool is demonstrated on the examples of a platinated double-stranded oligonucleotide and a modified RNA sequence. Experiments also reveal the unique dissociation behavior of platinated higher-order DNA structures.      

Synthesis of a new,C 2 Symmetric α,α - Bis-(Carboxymethyl) Substituted Nitroxide

The novel, diastereomeric meso- (cis) and (±)- (trans) nitroxides 2,5-dicarboxymethyl-2,5-dimethylpyrrolidine-1-oxyl have been synthesized via a dienolate based strategy. Both optically pure enantiomers of the C ₂ symmetric trans diastereomer have been obtained via resolution of the corresponding amine with dibenzoyltartaric acid.