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SMXL proteins are a plant-specific clade of type I HSP100/Clp-ATPases.SMXLgenes are found in virtually all land plants’ genomes. However, they have mainly been studied in angiosperms. InArabidopsis thaliana, three SMXL functional subclades have been identified: SMAX1/SMXL2, SMXL345 and SMXL678. Out of these, two subclades ensure transduction on endogenous hormone signals: SMAX1/SMXL2 are involved in KAI2-ligand (KL) signaling, while SMXL678 are involved in strigolactones (SLs) signaling. Many questions remain regarding the mode of action of these proteins, as well as their ancestral role. In light of recent discoveries in the liverwortMarchantia polymorpha,we addressed this second question by investigating the function of the fourSMXLgenes of the mossPhyscomitrium patens.We demonstrate that PpSMXL proteins are negative regulators of growth, involved in the likely conserved ancestral MAX2-dependent KL signaling pathway. However, PpSMXL proteins expressed inArabidopsis thalianaunexpectedly cannot replace SMAX1/SMXL2 function in KL signaling, whereas they can functionally replace SMXL4/5 and restore root growth. Therefore, the molecular function of SMXL could be conserved, but not their interaction network. Moreover, one PpSMXL clade also positively regulates transduction of the SL signal inP. patens, this function most probably having an independent evolutionary origin to angiosperms SMXL678.

KAI2 are plant α/β hydrolase receptors, which perceive smoke-derived butenolide signals (karrikins) and putative endogenous, yet unidentified phytohormones (KAI2-ligands, KLs). The number of functional KAI2 receptors varies among plant species. It has been suggested that KAI2 gene duplication and sub-functionalization plays an adaptative role for diverse environments or ligand diversification by altering the receptor responsiveness to specific KLs. Legumes represent one of the largest families of flowering plants and contain many essential agronomic crops. Prior to legume diversification, KAI2 underwent duplication, resulting in KAI2A and KAI2B. Integrating plant genetics, ligand perception and enzymatic assays, and protein crystallography, we demonstrate that Pisum sativum KAI2A and KAI2B act as receptors and enzymes with divergent ligand stereoselectivity. KAI2B has a stronger affinity than KAI2A towards the KAI2-ligand (-)-GR24 and remarkably hydrolyses a broader range of substrates including the strigolactone-like isomer (+)-GR24. We determine the crystal structures of PsKAI2B in apo and butenolide-bound states. The biochemical and structural analyses as well as recorded mass spectra of KAI2s reveal a transient intermediate on the catalytic serine and a stable adduct on the catalytic histidine, further illuminating the role of KAI2 not only as receptors but also as bona fide enzymes. Our work uncovers the stereoselectivity of ligand perception and catalysis by evolutionarily diverged KAI2 receptors in KAR/KL signaling pathways and proposes adaptive sensitivity to KAR/KL and strigolactone phytohormones by KAI2B.

The timing of leaf emergence at the shoot apical meristem, or plastochron, is highly regulated in plants. Among the genes known to regulate the plastochron in Arabidopsis (Arabidopsis thaliana), KLUH (KLU), orthologous to the rice (Oryza sativa) PLASTOCHRON1, encodes the cytochrome P450 CYP78A5, and is thought to act through generation of a still unknown mobile signal. As klu mutants display not only a short plastochron but also a branching phenotype reminiscent of strigolactone (SL) mutants, we investigated whether KLU/CYP78A5 is involved in SL biosynthesis. We combined a genetic approach, a parasitic plant seed germination bioassay to test klu root exudates, and analysis of transcript abundances of SL-biosynthesis genes in the Arabidopsis klu mutants. We demonstrate that KLU is not involved in the SL-biosynthesis pathway. Moreover, this work allowed us to uncover a new role for SL during Arabidopsis development in modulating plastochron via a KLU-dependent pathway. Globally our data reveal that KLU is required for plastochron-specific SL responses, a first indication of crosstalk between SL and the KLU-derived signal.

DWARF53 (D53) in rice (Oryza sativa) and its homologs in Arabidopsis (Arabidopsis thaliana), SUPPRESSOR OF MAX2-LIKE 6 (SMXL6), SMXL7 and SMXL8, are well established negative regulators of strigolactone signalling involved in shoot branching. Little is known of pea (Pisum sativum) homologs and whether D53 and related SMXLs are specific to strigolactone signalling pathways. Here, we identify two allelic pea mutants, dormant3 (dor3), and demonstrate through gene mapping and sequencing that DOR3 corresponds to a homolog of D53 and SMXL6/SMXL7, designated PsSMXL7. Phenotype analysis, gene expression, protein and hormone quantification assays were performed to determine the role of PsSMXL7 in bud outgrowth regulation and the role of PsSMXL7 and D53 in integrating strigolactone and cytokinin responses. Like D53 and related SMXLs, we show that PsSMXL7 is strigolactone degradable, and induces feedback upregulation of PsSMXL7 transcript. Here we reveal a system conserved in pea and rice, whereby CK also upregulates PsSMXL7/D53 transcripts, providing a clear mechanism for strigolactone and cytokinin cross-talk in the regulation of branching. Further deepening our understanding of the branching network in pea, we provide evidence that strigolactone acts via PsSMXL7 to modulate auxin content via PsAFB5, which itself regulates expression of strigolactone biosynthesis genes. We therefore show that PsSMXL7 is key to a triple hormone network involving an auxin-SL feedback mechanism and SL-CK crosstalk.

Strigolactones (SLs) are plant hormones exuded in the rhizosphere with a signaling role for the development of arbuscular mycorrhizal (AM) fungi and as stimulants of seed germination of the parasitic weeds Orobanche, Phelipanche and Striga, the most threatening weeds of major crops worldwide. Phelipanche ramosa is present mainly on rape, hemp and tobacco. P. ramosa 2a preferentially attacks hemp while P. ramosa 1 attacks rapeseed. The recently isolated Cannalactone 14 from hemp root exudates has been characterized as a non-canonical SL that selectively stimulates the germination of P. ramosa 2a seeds in comparison with P. ramosa 1. In the present work, we established that (−)-solanacol 5, a canonical orobanchol-type SL exuded by tobacco and tomato, possesses a remarkable selective germination stimulant activity for P. ramosa 2a seeds. We synthesized cannalactone analogs, named (±)-SdL19 and (±)-SdL118 which have an unsaturated acyclic carbon chain with a tertiary hydroxyl group and a methyl or a cyclopropyl group instead of a cyclohexane A-ring, respectively. (±)-SdL analogs are able to selectively stimulate P. ramosa 2a revealing that these minimal structural elements are key for this selective bioactivity. In addition, we showed that (±)-SdL19 is able to inhibit shoot branching in Pisum sativum and Arabidopsis thaliana, and induces hyphal branching in AM fungus R. irregularis, like SLs.

Shoot branching is a highly variable trait that evolves during plant development and is influenced by environmental and endogenous cues such as hormones. In particular, strigolactones (SLs) are hormones that play a key role in the control of shoot branching. Branch primordia, axillary buds formed in the leaf axils, display differential growth depending on their position in the plant and also respond to hormone signaling. In this chapter, we will describe how to quantify the degree of shoot branching in two plant model species, Arabidopsis and pea, commonly used to decipher the control of this complex trait. We will also propose several methods to perform treatments of SL or SL analogs, to investigate their bioactivity and effect on the shoot branching patterns of plants of different genotypes.

Shoot branching is a highly variable trait that evolves during plant development and is influenced by environmental and endogenous cues such as hormones. In particular, strigolactones (SLs) are hormones that play a key role in the control of shoot branching. Branch primordia, axillary buds formed in the leaf axils, display differential growth depending on their position in the plant and also respond to hormone signaling. In this chapter, we will describe how to quantify the degree of shoot branching in two plant model species, Arabidopsis and pea, commonly used to decipher the control of this complex trait. We will also propose several methods to perform treatments of SL or SL analogs, to investigate their bioactivity and effect on the shoot branching patterns of plants of different genotypes.

Introduction Strigolactones (SLs) are important plant hormones. They are difficult to analyse because they occur in very small concentrations especially in comparison with other plant hormones and other substances can interfere with their detection. Objective To develop a procedure for the extraction, purification and quantification of SLs from plant roots. Methodology Samples were prepared by extraction of plant root tissues with ethyl acetate. Then the extracts were further purified with silica column chromatography. The natural SLs in the final extracts were quantified using novel deuterium labelled SLs. The results of the methodology were compared with those of the procedure of Yoneyama and coworkers. Results This procedure required about 1-g root samples to detect and quantify simultaneously the SLs (orobanchyl acetate and fabacyl acetate) concentration with high reliability. Conclusion A method was developed for determining endogenous fabacyl acetate and orobanchyl acetate in plant tissue based on novel deuterium labelled standards. A method of orobanchol quantification using a synthetic SL GR24 as internal standard was proposed. Copyright © 2017 John Wiley & Sons, Ltd.

International audience; Strigolactone plant hormones control plant architecture and are key players in both symbiotic and parasitic interactions. They contain an ABC tricyclic lactone connected to a butenolide group, the D ring. The DWARF14 (D14) strigolactone receptor belongs to the superfamily of α/β-hydrolases, and is known to hydrolyze the bond between the ABC lactone and the D ring. Here we characterized the binding and catalytic functions of RAMOSUS3 (RMS3), the pea (Pisum sativum) ortholog of rice (Oryza sativa) D14 strigolactone receptor. Using new profluorescent probes with strigolactone-like bioactivity, we found that RMS3 acts as a single-turnover enzyme that explains its apparent low enzymatic rate. We demonstrated the formation of a covalent RMS3-D-ring complex, essential for bioactivity, in which the D ring was attached to histidine 247 of the catalytic triad. These results reveal an undescribed mechanism of plant hormone reception in which the receptor performs an irreversible enzymatic reaction to generate its own ligand.

Publication Inra prise en compte dans l'analyse bibliométrique des publications scientifiques mondiales sur les Fruits, les Légumes et la Pomme de terre. Période 2000-2012. http://prodinra.inra.fr/record/256699; International audience; Initially known for their role in the rhizosphere in stimulating the seed germination of parasitic weeds such as the Striga and Orobanche species, and later as host recognition signals for arbuscular mycorrhizal fungi, strigolactones (SLs) were recently rediscovered as a new class of plant hormones involved in the control of shoot branching in plants. Herein, we report the synthesis of new SL analogs and, to our knowledge, the first study of SL structure-activity relationships for their hormonal activity in garden pea (Pisum sativum). Comparisons with their action for the germination of broomrape (Phelipanche ramosa) are also presented. The pea rms1 SL-deficient mutant was used in a SL bioassay based on axillary bud length after direct SL application on the bud. This assay was compared with an assay where SLs were fed via the roots using hydroponics and with a molecular assay in which transcript levels of BRANCHED1, the pea homolog of the maize TEOSINTE BRANCHED1 gene were quantified in axillary buds only 6 h after application of SLs. We have demonstrated that the presence of a Michael acceptor and a methylbutenolide or dimethylbutenolide motif in the same molecule is essential. It was established that the more active analog 23 with a dimethylbutenolide as the D-ring could be used to control the plant architecture without strongly favoring the germination of P. ramosa seeds. Bold numerals refer to numbers of compounds.

The function of PsBRC1, the pea (Pisum sativum) homolog of the maize (Zea mays) TEOSINTE BRANCHED1 and the Arabidopsis (Arabidopsis thaliana) BRANCHED1 (AtBRC1) genes, was investigated. The pea Psbrc1 mutant displays an increased shoot-branching phenotype, is able to synthesize strigolactone (SL), and does not respond to SL application. The level of pleiotropy of the SL-deficient ramosus1 (rms1) mutant is higher than in the Psbrc1 mutant, rms1 exhibiting a relatively dwarf phenotype and more extensive branching at upper nodes. The PsBRC1 gene is mostly expressed in the axillary bud and is transcriptionally up-regulated by direct application of the synthetic SL GR24 and down-regulated by the cytokinin (CK) 6-benzylaminopurine. The results suggest that PsBRC1 may have a role in integrating SL and CK signals and that SLs act directly within the bud to regulate its outgrowth. However, the Psbrc1 mutant responds to 6-benzylaminopurine application and decapitation by increasing axillary bud length, implicating a PsBRC1-independent component of the CK response in sustained bud growth. In contrast to other SL-related mutants, the Psbrc1 mutation does not cause a decrease in the CK zeatin riboside in the xylem sap or a strong increase in RMS1 transcript levels, suggesting that the RMS2-dependent feedback is not activated in this mutant. Surprisingly, the double rms1 Psbrc1 mutant displays a strong increase in numbers of branches at cotyledonary nodes, whereas branching at upper nodes is not significantly higher than the branching in rms1. This phenotype indicates a localized regulation of branching at these nodes specific to pea.

Amnesic shellfish poisoning (ASP) is caused by consumption of contaminated seafood that has accumulated kainic acid or kainoid analogues such as domoic acid. Among the different ASP bioassays, immunoassays are an attractive alternative to the in vivo mouse bioassay. Herein, we report the synthesis and bioconjugation of two new haptens for the generation of a specific antibody against members of the kainoid family.

International audience; This paper reports the detection of okadaic acid (OA) as a Diarrheic Shellfish Poisoning (DSP) toxin with an acoustic wave platform in real-time. According to the FDA, the threshold for safe consumption of shellfish is 20 μg of OA for 100 g of shellfish tissue. The high gravimetric sensitivity of Love wave acoustic devices allow, in liquid media, immuno-detection thanks to immobilized specific antibodies. The biosensor is composed of two lines, one for the test and one used as a reference. Sensitive films were deposited through a PolyDiMethylSiloxane (PDMS) microfluidic chip. On both lines, anti-okadaic acid antibodies (OA-Ab) and saturating agents were successively injected under continuous flow with controlled flow rate. On the test line, okadaic acid (OA) was injected while an unspecific peptide (6×Histidine, 6×His) was used on the control line. On both lines, polyclonal OA-Ab were re-injected a second time to reveal previously fixed OA on the test line. Measured frequency shifts were three times higher on test lines than on control lines. In these conditions, for only 2 μg of OA used for detection, the acoustic wave platform could detect DSP toxins with only 10 g of shellfish tissue.

Silylboranes with aromatic substituents linked to boron and silicon exhibit an unexpected absorption band in the UV–Vis spectral region. When polar groups were introduced, a marked solvatochromic effect was observed in their fluorescence emission spectra, revealing a strong excited state dipole moment. Semi-empirical MNDO/d and AM1 calculations showed that, upon UV excitation, the polarity of the Si–B bond increased and the aromatic π-electrons migrated toward the Si–B bond, consistent with experimental observations.

A multipurpose Love acoustic wave biosensor is described in this article. As mass loading is one of the main effect involved in acoustic wave sensors, a great range of biomolecules could be detected using such sensors. In this way, the antibody/antigen binding property was used to immobilise the target species. We first compared different coupling agents to link the antibodies sensitive layer to the SiO2 sensor surface. Results showed that GPTS monolayer, allowing covalent attachment of antibodies bioreceptors, is better suited than DTSP and protein G. It permits to obtain a dense, stable and reproducible sensitive layer of antibodies. Then, different biological species with different size and shape like proteins, bacteriophages or bacteria were detected using such sensor. Different models have been chosen to validate the effective detection of a large species range: an anti-mouse antibody has been used to simulate small molecules (

La recuperation de la matiere organique des schistes bitumineux de Tarfaya a ete effectuee dans des conditions subcritiques au moyen du phenol comme solvant. Les differentes analyses effectuees sur les huiles produites ont clairement mis en evidence le role du phenol dans l'augmentation du rendement de recuperation, de la quantite des maltenes, des aromatiques et dans la reduction du taux de soufre dans les huiles des schistes bitumineux marocains.

A series of organosilylboranes has been investigated by IR spectroscopy and semiempirical calculations (MNDO/d force field methods). Computational studies afforded Si–B stretching wavenumbers in good agreement with the experimental IR bands observed in the range of 480–650 cm −1 . It was shown that these characteristic Si–B bond vibrations depend on the structure of molecules and on the size of substituting groups. Thus, compounds possessing small and medium substituting groups (H, Me) and those having a symmetry element give pure Si–B stretching bands. In the case of silylboranes bearing bulky groups, assignments of bands involving Si–B vibrators were achieved via comparison of experimental and theoretical IR spectra with those of reference molecules containing the parent organosilyl- or organoboryl moieties. An experimental absorption band near 600 cm −1 could reasonably be assigned to ν (Si–B).

Novel stable organosilylboranes possessing dimesityl groups attached to boron were synthesised. They gave an addition reaction with terminal acetylenic hydrocarbons in the presence of a transition metal complex. Thus, (diphenylmethylsilyl)dimesitylborane and (diphenyl-tert-butylsilyl)dimesitylborane reacted in good yields with phenylacetylene and alk-1-ynes in the presence of Pd2(dba)3(etpo)2 as a catalyst. The structures of the products were determined by NMR spectroscopy using INEPT techniques coupled to computational simulation. Various heteronuclear coupling constants J 13 C − H and J 29 Si − H were determined for the first time in this series. The results showed that the dimesitylboryl group added to the terminal acetylenic carbon atom and the organosilyl group to the internal carbon atom, according to a regio- and stereoselective syn-addition.

International audience; : Strigolactones (SLs) are known not only as plant hormones, but also as rhizosphere signals for establishing symbiotic and parasitic interactions. The design of new specific SL analogs is a challenging goal in understanding the basic plant biology and is also useful to control plant architectures without favoring the development of parasitic plants. Two different molecules (23 (3'-methyl-GR24), 31 (thia-3'-methyl-debranone-like molecule)) already described, and a new one (AR36), for which the synthesis is presented, are biologically compared with the well-known GR24 and the recently identified CISA-1. These different structures emphasize the wide range of parts attached to the D-ring for the bioactivity as a plant hormone. These new compounds possess a common dimethylbutenolide motif but their structure varies in the ABC part of the molecules: 23 has the same ABC part as GR24, while 31 and AR36 carry, respectively, an aromatic ring and an acyclic carbon chain. Detailed information is given for the bioactivity of such derivatives in strigolactone synthesis or in perception mutant plants (pea rms1 and rms4, Arabidopsis max2 and, max4) for different hormonal functions along with their action in the rhizosphere on arbuscular mycorrhizal hyphal growth and parasitic weed germination.

Strigolactone (SL) mutants in diverse species show reduced stature in addition to their extensive branching. Here, we show that this dwarfism in pea (Pisum sativum) is not attributable to the strong branching of the mutants. The continuous supply of the synthetic SL GR24 via the root system using hydroponics can restore internode length of the SL-deficient rms1 mutant but not of the SL-response rms4 mutant, indicating that SLs stimulate internode elongation via RMS4. Cytological analysis of internode epidermal cells indicates that SLs control cell number but not cell length, suggesting that SL may affect stem elongation by stimulating cell division. Consequently, SLs can repress (in axillary buds) or promote (in the stem) cell division in a tissue-dependent manner. Because gibberellins (GAs) increase internode length by affecting both cell division and cell length, we tested if SLs stimulate internode elongation by affecting GA metabolism or signaling. Genetic analyses using SL-deficient and GA-deficient or DELLA-deficient double mutants, together with molecular and physiological approaches, suggest that SLs act independently from GAs to stimulate internode elongation.

Using a new procedure, substituted disilylmethanes have been prepared from chlorosilanes, dichloromethane, and magnesium in tetrahydrofuran. Bis(chlorosilyl)methanes can be used as comonomers for the synthesis of polysilacarbosilanes, which are transformed into polycarbosilanes, precursors of silicon carbide.

Polycondensation of 2,4-disilapentane in the presence of titanium or zirconium-based catalysts afforded original poly(2,4-disilapanentane) oligomers useful as ceramic precursors.

International audience; A new general access to A-ring aromatic strigolactones, a new class of plant hormones, has been developed. The key transformations include in sequence ring-closing metathesis, enzymatic kinetic resolution and a radical cyclization with atom transfer to install the tricyclic ABC-ring system. The activity as plant hormones for the inhibition of shoot branching in pea of various analogues synthesized by this strategy is reported.

A trans-silylation route to 1,3-dichloro-l,3-dihydridodisilazanes, a novel class of polyfunctional disilazane, is described. Thus, heating hexamethyl- or heptamethyl-disilazane under reflux in the presence of an excess of dichlorohydrogenosilane R 1 SiHCl 2 , led to compounds of formula (R 1 ClHSi) 2 NR 2 (R 1 = Me, Et, Vi or Ph and R 2 = H; R 1 = Me and R 2 = Me) in high yield. The exchange of chlorinated organosilicon moieties was strongly facilited by a catalytic amount of ( π Bu 4 N)F. Interpretation of the results and a few chemical properties of these novel disilazanes are reported.

International audience; A very-long-chain (C22) organosilicon self-assembled monolayer (SAM) with terminal glycidyl groups was used to immobilize antibodies on the silica waveguide of a Love mode surface acoustic wave (SAW) immunosensor. This route enabled us to specifically detect, in real time, living Escherichia coli bacteria by using monoclonal anti-E. coli antibodies, leading to a marked sensor response in liquid aqueous medium. Conversely, no bacteria detection could be observed by this direct method upon functionalization of the waveguide surface by a (3-glycidoxypropyl) trimethoxysilane (GPTS) monolayer. This improvement was attributed to a surface smoothing effect resulting from the very-long-chain SAM and a better accessibility of the surface epoxide groups.

Novel glycidyl-terminated organosilicon coupling agents possessing a trialkoxysilyl head group and a very long hydrocarbon chain (C22) were synthesized. Their ability to afford densely packed self-assembled monolayers (SAMs) grafted on silica-based surfaces was investigated. Transmission FT-IR spectra showed that the most regular films were obtained by using trichloracetic acid as the catalyst (10 M%). Atomic force microscopy (AFM) and optical ellipsometry were consistent with well ordered monolayers exhibiting a marked decrease of the surface roughness. Epifluorescence microscopy revealed that these SAMs possessed a better surface reactivity than monolayers obtained with the commercially available (3-glycidoxypropyl) trimethoxysilane (GPTS) upon grafting of a fluorescent probe (dansylcadaverin). Moreover, direct attachment of fluorescent antibodies (RAG-TRITC) through covalent binding led to higher mean fluorescence intensities, showing that these new SAMs possess high potential for the immobilization of biological molecules.

International audience; A carotenoid-derived hormonal signal that inhibits shoot branching in plants has long escaped identification. Strigolactonesare compounds thought to be derived from carotenoids and are known to trigger the germination of parasitic plant seeds andstimulate symbiotic fungi. Here we present evidence that carotenoid cleavage dioxygenase 8 shoot branching mutants of peaare strigolactone deficient and that strigolactone application restores the wild-type branching phenotype to ccd8 mutants.Moreover, we show that other branching mutants previously characterized as lacking a response to the branching inhibitionsignal also lack strigolactone response, and are not deficient in strigolactones. These responses are conserved in Arabidopsis.In agreement with the expected properties of the hormonal signal, exogenous strigolactone can be transported in shoots andact at low concentrations. We suggest that endogenous strigolactones or related compounds inhibit shoot branching inplants. Furthermore, ccd8 mutants demonstrate the diverse effects of strigolactones in shoot branching, mycorrhizalsymbiosis and parasitic weed interaction.

International audience; Treatment of cellulose yarns by a polysiloxane followed by a fast pyrolysis step gave carbon fibres exhibiting strong enhancement of their mechanical resistance. To account for the beneficial effect of the polysiloxane, an investigation of the pyrolysis mechanisms was performed on a model system based on cellobiose and a polysiloxane resin. A chemical interaction between cellobiose and the resin (e.g. grafting of siloxane fragments onto the cellobiose) was established by using various physicochemical analysis techniques: nuclear magnetic resonance (NMR), photoelectron spectrometry (XPS), electronic paramagnetic resonance (EPR), Flash pyrolysis–gas chromatography–mass spectrometry (FP/GC/MS) and IR.

The efficiency of a monomolecular film of (3-glycidoxypropyl) trimethoxysilane (GPTS) on a shear horizontal guided (Love) acoustic wave immunosensor to detect whole Escherichia coli ( E. coli ) bacteria is demonstrated. Direct anti- E. coli antibodies grafting onto the sensor surface did not lead to a significant bacteria immobilisation, partially attributed to the SiO 2 sensor surface roughness. An innovative method has been set up to get around this difficulty and to detect whole bacteria. It consists in grafting goat anti-mouse antibodies (GAM) onto the sensor surface in a first step and introducing E. coli bacteria mixed with anti- E. coli antibodies onto the sensor in a second step. We describe the characteristics of such a technique like sample preparation time (lower than 30 min) and temperature improvements. A 37 °C experimental temperature led to the fastest bacteria binding kinetic, reducing the total analysis time. This method enables to keep the specificity of the antibody/antigen interaction and provides significant results in less than 1 h. This leads to a detection threshold of 10 6 bacteria/ml in a 500 μl chamber.

An acoustic Love wave immunosensor dedicated to detect biological species such as bacteria, viruses or toxins is described in this paper. We present and analyze results of antibody grafting on the Love wave device using GPTS as coupling agent between SiO2 sensor surface and the sensitive biomembrane layer composed of antibodies. Goat anti-mouse (GAM) antibodies at concentrations from 2μg/ml to 50 μg/ml were introduced on the sensor brass cell. The saturation of the sensor surface by antibodies appears at a concentration of 20 μg/ml. The detection threshold of this primary antibody is around 2 μg/ml, and the lowest concentration allowing antigen detection is around 5 μg/ml.

Self-assembled monolayers grafted onto silicon surfaces were obtained from the hydrosilylation products by trialcoxysilanes of naturally occurring phenolic lipid allyl ethers. The as-obtained materials were characterized by various physical and physicochemical methods. Thus, contact angles of water drops showed that they possess very high hydrophobicity. Their excellent regularity was corroborated by AFM microscopy. The frequencies of the stretching CH2 infrared modes indicate the presence of alkyl chains mainly in the trans/trans conformation. Additionally, optical ellipsometry and quartz microbalance measurements enabled us to estimate the thickness of the films. The results, as a whole, are in good agreement with the formation of densely packed monolayers.

International audience; Novel silsesquioxane thin films were conveniently synthesized by the sol-gel route under mild conditions. Thus, a sol was prepared from 4,4′-bis(triethoxysilyl)-1,1′-biphenyl (4,4′-BTEBp) under a hydroalcoholic medium without a surfactant, deposited by spin-coating on silica supports, and dried at 280 °C. The resulting biphenylene-bridged films exhibited very smooth surfaces, excellent mechanical behavior and no cracks. Moreover, SEM and TEM studies showed flawless, homogeneous interfaces with silica substrates. The acoustic waveguide properties of these films on piezoelectric quartz microsensors were investigated at high frequency through a network analyzer. For an optimal thickness close to 1 μm, a marked frequency shift of the main broad lobe and a decrease of the insertion loss were observed. These results show a strong effect of the waveguide for trapping the acoustic energy, promising an unprecedented ability to provide a new generation of sensors. The capability of this device in the detection of mass is also demonstrated through the immobilization of Bovine Serum Albumin (BSA). This novel approach appears very promising in view of the development of surface acoustic wave sensors and biosensors.

Infrared and Raman spectra of poly(hydrogenosilmethylenes) and of poly(chlorsosil-methylenes) are recorded and iterpreted. The results show that in the γ(SiH) region and also below 850 cm −1 where the γ(CSiC) and the γ(SiCSi) stretching vibrations are found, it is possible to distinguish the different structural units of the derivatives, and to determine the chains lengths for n = 1–5. lf n= 1, two rotamers are observed for both Si H and Si Cl molecules.

AlCl 3 catalyse la reaction d'echange CH 3 -Cl sur le silicium du poly(dimethylsilylene) methylene(I) (obtenu a partir du tetramethyl-1,1,3,3 disila-1,3 cyclobutane)

In the presence of lithium and in tetrahydrofuran as solvent, trimethylchlorisilane reacts with tetralin to give two new compounds, (I) and (II). The latter when refluxed with acetic acid leads to a new monosilylated olefin (III). The study of the desilylation mechanism leads to envisage an isomerization of allyl- into vinyl-silane.

In the presence of a Lewis acid (AlCl3, InCl3, GaCl3), acyl chlorides react with allyltrimethylsilane to give the corresponding allyl ketones, CH2CHCH2COR, in good yields. Substituted allylsilanes, synthesized by 1,4-disilylation of conjugated dienes, give a similar reaction. The electrophilic substitution of SiMe3 by a COR group occurs with allylic rearrangement and therefore silylated β,γ-ethylenic ketones, , are obtained. In most cases the allylic ketones prepared isomerize easily to the corresponding conjugated ketones; ketones having the formula CH2CHCH2COR lead uniquely to the trans-,propenylketones, MeCHCHCOR.

Thermolysis of linear or cyclic polydimethylsilanes into polycarbosilanes by Yajima's method has been studied by analyzing the gases evolved by means of gas chromatography and mass spectroscopy. About 20% of silicon was eliminated as methylsilanes during the reaction. Furthermore these results suggest some differences in the mechanisms of reactions with and without catalyst, as in the structures of the polycarbosilanes obtained.

Sulphonation by trimethylsilyl chlorosulphonate of various substituted silicon compounds is regiospecific or highly regioselective at the silicon atom, the reaction order is found to be: allyl > α-naphthyl > phenyl > vinyl. Sulphonation of various mono- and di-silylated derivatives leads to trimethylsilylmono- and in some cases to trimethylsilyldisulphonates which by hydrolysis form new sulphonic acids. The orientation of the sulphonation is determined by the position of the silicon atom. The nature of cyclohexyl hinders sulphonation (cyclo-C 6 H 11 Si is much less reactive than MeSi), while cyclopropanyl, due to its π-character, is much more reactive.

The hydroperoxidation of various allylsilanes by singlet oxygen has been studied. The regioselectivity of this reaction compared to those of ethyl azodicarboxylate and 4-phenyl-1,2,4-triazoline-3,5-dione, is discussed. Mechanisms are considered in the general field of the ene reaction applied to allylic organometallic Group IVB compounds. The structures of the new products (alcohols, urazoles, hydrazines) have been determined, directly or after transformations, by NMR spectroscopy.

Polycarbosilane contenant des groupes (methyl et methyldeuteriosilylene. Reticulation terminale. Reduction du poly[(chlorosilylene)methylene]