Bernard Bennetau

The estrogenic activity of certain phytoestrogens in the siberian sturgeon Acipenser baeri

Various phytoestrogens such as formononetin, daidzein, genistein and equol were synthesized. Their purity was assessed by various analytical techniques including melting point determination, thin-layer chromatography (TLC), infra-red spectra (i.r. spectra), nuclear magnetic resonance (1H- and 13C-NMR) and gas chromatography coupled with mass spectrometry (GC-MS). The estrogenic activity of these compounds, as well as biochanin A and coumestrol, was biologically tested by the induction of vitellogenin secretion in yearling sturgeon and compared to the activity of estradiol-17 beta. Pure daidzein, biochanin A, genistein, equol and coumestrol all had estrogenic activity as assessed by their induction of hepatic synthesis of vitellogenin when administrated intraperitoneally to yearling Siberian sturgeon. Coumestrol seemed to be the most potent compound, inducing the most vitellogenin secretion with the lowest dose administered. Formononetin was inactive when administered by the intraperitoneal route. All the phytoestrogens tested were considerably less potent than estradiol-17 beta.

Identification and characteristics of new volatile thiols derived from the hop (Humulus luplus L.) cultivar Nelson Sauvin.

Nelson Sauvin (NS) is a unique hop cultivar that was bred and grown in New Zealand. This hop gives a specific flavor (exotic fruit-like, white wine-like) to finished beers. However, the key compounds of this flavor have not yet been identified. We have attempted to identify the specific flavor compounds derived from NS. We focused on certain volatile thiols that are well-known to contribute to wine flavors, especially Sauvignon Blanc. The product made from NS (NS product) lost its specific flavor by contact with copper. Copper is well-known as an absorber of thiols in the field of wine flavor investigations. Therefore, it might point to the existence of thiols. We analyzed the NS product by GC-FPD, GC-olfactometry and GC-MS, and identified two new volatile thiols, 3-sulfanyl-4-methylpentan-1-ol (3S4MP), and 3-sulfanyl-4-methylpentyl acetate (3S4MPA). These compounds have a grapefruit-like and/or rhubarb-like odor, similar to that of Sauvignon Blanc. We quantified these compounds in the NS products and determined their thresholds. As a result, 3S4MP contained about 2-fold of its threshold in beers, and 3S4MPA was included below its threshold. However, it was confirmed that 3S4MP enhanced the flavors of 3S4MPA by synergy. Therefore, we concluded that both of the new volatile thiols would contribute to the specific odor of beers produced with NS.

Analysis of the diastereoisomers of the cysteinylated aroma precursor of 3-sulfanylhexanol in Vitis vinifera grape must by gas chromatography coupled with ion trap tandem mass spectrometry

The diastereoisomeric distribution of S-3-(hexan-1-ol)cysteine (P-3SH), the cysteinylated precursor of 3-sulfanylhexan-1-ol (3SH) in Vitis vinifera grape juice, was determined by a new method. This procedure is based on the purification of P-3SH in a small volume of must (500 microL) by affinity chromatography, followed by the separation of chiral molecules in derivative forms by gas chromatography coupled with ion trap tandem mass spectrometry (GC-MS/MS). The diastereoisomers were easily separated using heptafluorobutyric anhydride and heptafluorobutanol (HFBA and HFOH) as derivatization reagents. Method validation was conducted using samples of grape juice, synthetic must, fermenting must, and wine that were fortified with P-3SH at concentrations of 0.6 and 2.5 microM. The relative standard deviation (RSD) and limit of detection (LOD) of the GC-MS/MS method were 4.6% and 1.5 nM, respectively. P-3SH assays in Bordeaux white grape juice affected by Botrytis cinerea showed an unusually increased proportion of the RS form of the precursor (approximately RR:RS=30:70) as compared to a diastereoisomer ratio (in the vicinity of 50:50) in healthy grape juice.

PM-IRRAS Investigation of Self-Assembled Monolayers Grafted onto SiO2/Au Substrates

Polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) was used to characterize self-assembled monolayers (SAMs). Novel ester-terminated organosilicon coupling agents possessing a trialkoxysilyl headgroup and a urea group in the linear alkyl chains (4) were synthesized and grafted onto SiO(2)/Au substrates (SiO(2) film of 200 Å thickness deposited on gold mirror). This composite substrate allowed the anchoring of SAMs and preserved the high reflectivity for infrared radiation. PM-IRRAS spectra with very high signal-to-noise ratios have been obtained in the mid-infrared spectral range allowing monitoring of the grafted SAMs. Quantitative analysis of the measured signal is described to compare PM-IRRAS and conventional IRRAS spectra. This quantitative analysis has been validated since the band intensities in the corrected PM-IRRAS and conventional IRRAS spectra are identical. Orientation information on the different functional groups has been obtained comparing the corrected PM-IRRAS spectrum with the one calculated using isotropic optical constants of ester-terminated organosilicon coupling agents 4. The carbonyls of the urea groups are preferentially parallel to the substrate surface favoring intermolecular hydrogen bonding and consequently a close packing of the molecules attached to the surface. By contrast, the alkyl chains present gauche defects and are poorly oriented.

A new immunosensor for breast cancer cell detection using antibody-coated long alkylsilane self-assembled monolayers in a parallel plate flow chamber

We designed a new efficient and reliable immunosensor and demonstrated its analytic performance to capture breast cancer MCF7 and T47D cells, under laminar flow, onto antibody-coated long alkylsilane self-assembled monolayers (SAMs) in a parallel plate flow chamber. The surface floor of the laminar flow chamber was grafted with an amino-terminated long alkyl chain spacer, 21-aminohenicosyl trichlorosilane (AHTS) followed by tethering a specific monoclonal antibody directed against the human epithelial cell adhesion molecule (EpCAM) antigen, which is overexpressed in primary breast cancer. Properties of the AHTS- and antibody-grafted surface floor were compared to that of surface floors coated with the short alkyl spacers 3-glycidoxy-propyl trimethoxysilane (GPTS) or 3-aminopropyl triethoxysilane (APTES) and antibodies. A theoretical model was constructed according to the geometry of the flow chamber in order to calculate the trajectories that would use cell flows. Cell capture experiments demonstrated that cell immobilization was optimized throughout the whole flow chamber. High cell capture was yielded on antibody-tethered long alkyl AHTS surface. This new procedure offers multiple advantages: a versatile tool readily applied to a panel of purified antibodies, an enrichment of cell immobilization using repetitive cell flow, and a stable capturing surface suitable for long term storage and handling.

Nouvelle voie d'acces aux cetones α-alleniques

Resume Propargyltrimethylsilane and 1,3-bis(trimethylsilyl)propyne react with acyl halides to afford α-allenic ketones. In the case of 1,3-bis(trimethylsilyl)-3-methyl-1-butyne a 1,3-dienic ketone is obtained by a process which involves first a SiC propargylic bond cleavage under acidic conditions.

Fonctionnalisation régiosélective en position 2 de benzènes 1,3-disubstitués

Abstract Functionalisation in 2 position of benzenes 1,3-disubstituted by para -directing groups has been investigated, involving 2-trimethylsilylated intermediates when the classical methods (particularly these involving the anion in 2 position) are ineffective. Thus 2-trimethylsilyl derivatives of 1,3-dihalo- or 1,3-dimethoxybenzene have been prepared in good yields. Their conversion into the corresponding 1,2,3-trisubstituted benzenes has been conveniently performed upon acetylation, iodination or sulfonation, except in the case of the sulfonation of the 1,3-dimethoxylated compound in which the ipso effect of the silyl group is surpassed by the directing effect of the methoxy substituents. In contrast, whith the same substrate, cyanation in position 2 was successfully carried out using chlorosulfonyl isocyanate: to our knowledge this reaction is the first example of substitution of a trimethylsilyl by a cyano group in the aromatic series.

REGIOSPECIFIC SYNTHESIS OF MIXED 2,3-DIHALOBENZOIC ACIDS AND RELATED ACETOPHENONES VIA ORTHO-METALATION REACTIONS

Abstract Concise general routes to mixed 2,3-dihalobenzoic acids and related acetophenones based on directed ortho -metalation and ipso-desilylation reactions are described.

Un nouveau synthon organosilicie : Le benzyltrimethylsilane

Abstract In the presence of tetrabutylammonium fluoride (TBAF) as the catalyst, benzyltrimethylsilane adds to aldehydes and ketones to afford, upon hydrolysis, the corresponding alcohols. The use of PhCH 2 SiMe 3 as a general benzylation reagent is here reported for the first time.

Functionalized hydrogen-bonding self-assembled monolayers grafted onto SiO2 substrates.

A novel urea coupling agent possessing a vinyl-terminal group and trimethoxysilyl anchoring group was synthesized and grafted onto SiO(2)/Au substrates. This ureido coupling agent exhibits a good capacity to directly yield homogeneous SAMs with a surface smoothing. Polarization modulation infrared reflection-absorption spectroscopy (PM-IRRAS) was used to monitor these SAMs. Indeed, the different functional groups (alkyl chain, urea, and vinyl) of this coupling agent were clearly observed in the PM-IRRAS spectra. Chemical modifications of the terminal function for the covalent immobilization of biomolecules were monitored by PM-IRRAS for the first time. We have demonstrated the successful reactions of the conversion of the vinyl-terminated SAMs successively into SAM-COOH and SAM-NHS without any degradation of the monolayer. The reactivity of activated esters was successfully investigated in order to immobilize the protein A.