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2003

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A LC/APCI-MS/MS method for analysis of imidacloprid in soils, in plants, and in pollens

Imidacloprid, the most used systemic insecticide, is suspected of having harmful effects on honeybees at nanogram per bee or at microgram per kilogram levels. However, there is a lack of methodology to detect imidacloprid and its metabolites at such low levels. We developed a method for the determination of low amounts of imidacloprid in soils, plants (leaves and flowers), and pollens by using HPLC coupled to tandem mass spectrometry (APCI-MS/MS). Extraction, separation, and detection were performed according to quality assurance criteria, to Good laboratory Practice, and to criteria from the directive 96/23/EC, which is designed for banned substances. The linear range of application is 0.5-20 mug/kg imidacloprid in soils, in plants, and in pollens, with a relative standard deviation of 2.9% at 1 mug/kg. The limits of detection and of quantification are LOD = 0.1 mug/kg and LOQ = 1 mug/kg, respectively. For the first time, this study permitted us to follow the fate of imidacloprid in the environment. When treated, flowers of sunflower and maize contain average values of similar to10 mug/kg imidacloprid. Ibis explains that pollens from these crops are contaminated at levels of a few micrograms per kilogram, suggesting probable deleterious effects on honeybees.

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A molecularly cloned Schwarz strain of measles virus vaccine induces strong immune responses in Macaques and transgenic mice

Live attenuated RNA viruses make highly efficient vaccines. Among them, measles virus (W) vaccine has been given to a very large number of children and has been shown to be highly efficacious and safe. Therefore, this vaccine might be a very promising vector to immunize children against both measles and other infectious agents, such as human immunodeficiency virus. A vector was previously derived from the Edmonston B strain of MV, a vaccine strain abandoned 25 years ago. Sequence analysis revealed that the genome of this vector diverges from Edmonston B by 10 amino acid substitutions not related to any Edmonston subgroup. Here we describe an infectious cDNA for the Schwarz/Moraten strain, a widely used MV vaccine.

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Alpha-helical or ß-sheet structure. A discrimating factor for peptide properties ?

This review is a general survey of the main physico-chemical properties likely to distinguish a-helical from ß-sheet structured peptides. After giving a few basic notions of protein structures, their hierarchy and the determination methods, it focuses on the secondary structures. A large part of the review is devoted to the parameters affecting the preferential folding of a peptide chain into an a-helix or a ß-sheet. The environmental conditions of peptide polymorphism in solution but also at interfaces are described. The interactions of both kind of peptides with lipid membranes and the ensuing biological properties are described in the last part of the review. The topic is illustrated, throughout the text, by the behaviour of natural or designed antimicrobial peptides.

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An ORF2 protein-based ELISA for porcine circovirus type 2 antibodies in post-weaning multisystemic wasting syndrome

Porcine circovirus type 2 (PCV2) plays a crucial role in the pathogenesis of post-weaning multisystemic wasting syndrome (PMWS) in swine. As PCV2 displays significant homology with PCV1 (a non-pathogenic virus) at the nucleotide and amino-acid level, a discriminative antigen is needed for specific serological diagnosis. The ORF2-encoded capsid protein from PCV2 was used to develop an indirect enzyme-linked immunosorbent assay (ELISA). GST-fused capsid protein from PCV2 and GST alone (both expressed in recombinant baculovirus-infected cells) were used as antigens for serodiagnosis. The specificity of the ELISA for detection of PCV2 antibodies was demonstrated in sera from pigs experimentally infected with PCV1, PCV2 and other swine viruses. The semi-quantitative nature of the test was evaluated versus an immunoperoxidase monolayer assay (IPMA). The ELISA was performed on 322 sera from pigs in eight Brittany herds and compared with IPMA. The sensitivity (98.2%) and specificity (94.5%) of this test were considered suitable for individual serological detection. High PCV2 seroprevalence was found in sows and pigs at the end of the growth phase (18-19 weeks) in all eight herds. The seroprevalence in piglets (11-17 weeks) was statistically correlated with clinical symptoms of PMWS (93% in affected versus 54%, in non-affected farms). A cohort study performed in PMWS-free farms showed that 57% of piglets exhibited active seroconversion after 13 weeks, indicating that PCV2 infection occurred earlier in PMWS-affected piglets

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Binding discrimination of MutS to a set of lesions and compound lesions (base damage and mismatch) reveals its potential role as a cisplatin-damaged DNA sensing protein

The DNA mismatch repair (MMR) system plays a critical role in sensitizing both prokaryotic and eukaryotic cells to the clinically potent anticancer drug cisplatin. It is thought to mediate cytotoxicity through recognition of cisplatin DNA lesions. This drug generates a range of lesions that may also give rise to compound lesions resulting from the misincorporation of a base during translesion synthesis. Using gel mobility shift competition assays and surface plasmon resonance, we have analyzed the interaction of Escherichia coli MutS protein with site-specifically modified DNA oligonucleotides containing each of the four cisplatin cross-links or a set of compound lesions. The major 1,2-d(GpG) cisplatin intrastrand cross-link was recognized with only a 1.5-fold specificity, whereas a 47-fold specificity was found with a natural G/T containing DNA substrate.

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Carbohydrate-lectin interactions assessed by surface plasmon resonance

The specificity, the strength, the kinetics and some thermodynamic parameters of sugar-protein interactions are easily assessed by surface plasmon resonance (SPR). This paper intends to present both theoretical and practical considerations. This includes : the principle of SPR, the analysis according to Langmuir and Scatchard, the problems linked either to mass transport limitation, to the heterogeneity of the immobilized ligand density or to the non-linearity due to cluster effects. The non-linearity may be taken into account by either one of two ways : the fractal or the Sips approaches that have been developed with the aim of linearizing the data.

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