Molluscicidal saponins from cornus florida L.

The molluscicidal principle of Cornus florida L. (Cornaceae) has been isolated from the methanolic bark extract by droplet counter-current chromatography (DCC). The structure of the active compounds has been determined as sarsapogenin-O-β-D-xylopyranosyl-(1 → 2)-β-D-galactopyranoside (2) and sarsapogenin-O-β-D-glucopyranosyl-(1 → 2)-β-D-galactopyranoside (3) .     

In situ measurements of nanotube dimensions in suspensions by depolarized dynamic light scattering

We show that the dimensions of carbon nanotubes (CNTs) in suspension can be characterized by depolarized dynamic light scattering. Taking advantages of this in situ technique, we investigate in detail the influence of sonication procedures on the length and diameter of CNTs in surfactant solutions. Sonication power is shown to be particularly efficient at unbundling nanotubes, whereas a long sonication time at low power can be sufficient to cut the bundles with limited unbundling. We finally demonstrate the influence of CNT dimensions on the electrical properties of CNT fibers. Slightly varying the sonication conditions, and thereby the suspended nanotube dimensions, can affect the fibers conductivity by almost 2 orders of magnitude.     

Contribution à la phytochimie du genre Gentiana IX. Etude de composés flavoniques et xanthoniques dans les feuilles de gentiana CampestrisL. 1ère communication

Two new xanthone-O-glycoside, the 1,3,5-trihydroxy-xanthone-8-O-β-D -glucopyranoside ( 3 ), the 1,5-dihydroxy-3-methoxyxanthone-8-O-β-D -glucopyranoside ( 4 ), have been isolated from the leaves of Gentiana campestris L . by means of column chromatography on polyamid. Two known xanthones ( 1 , 2 ) which are respectively the aglycones of 3 and 4 and a flavone: iso-orientine ( 5 ) have also been isolated and identified.     

Contribution à la phytochimie du genre Gentiana,XIII. Etude des composés flavoniques et xanthoniques dans les feuilles de Gentiana campestris L. 2ème communication

Phytochemistry of genus Gentiana XIII. Study of flavocic and xantonic compounds in the leaves of Gentiana campestris L. 2nd communication. By means of column chromatography on polyamide, we have isolated from the leaves of Gentiana campestris L. a new xanthone-O-glucoside, the 3,4-dimethoxy-5, 8-dihydroxy-xanthone-1-O-β-D-glucopyranoside ( 2 ) and its aglucone, the 3,4-dimethoxy-1,5,8-trihydroxy-xanthone ( 1 ). The C-glucosides mangiferin ( 3 ) and swertisin ( 4 ) have also been isolated and identified.     

Dichlorido[(S,RS)‐1‐diphenylphosphino‐2‐(ethylsulfanylmethyl)ferrocene]palladium(II)

The reaction of enantiomerically pure planar chiral ferrocene phosphine thioether with bis(acetonitrile)dichloridopalladium yields the title square‐planar mononuclear palladium complex as an enantiomerically pure single diastereoisomer, [PdFe(C₅H₅)(C₂₀H₂₀PS)Cl₂]. The planar chirality of the ligand is retained in the complex and fully controls the central chirality on the S atom. The absolute configuration, viz. S for the planar chirality and R for the S atom, is unequivocally determined by refinement of the Flack parameter.     

Fluorescent polymeric transducer for the rapid, simple, and specific detection of nucleic acids at the zeptomole level

We report the specific detection of a few hundred molecules of genetic material using a fluorescent polythiophene biosensor. Such recognition is based on simple electrostatic interactions between a cationic polymeric optical transducer and the negatively charged nucleic acid target and can be done in less than 1 h, simply and affordably, and without any chemical reaction. This simple system is versatile enough to detect nucleic acids of various lengths, including a segment from the RNA genome of the Influenza virus.     

Liquid crystal behavior of single-walled carbon nanotubes dispersed in biological hyaluronic acid solutions

We report the spontaneous liquid crystal phase separation of nanotubes (single-walled carbon nanotubes, SWNTs) stabilized in aqueous biological (hyaluronic acid, HA) solutions. Sonication of SWNTs in solutions of HA produced well-dispersed single-phase isotropic dispersions which, over time, phase separated into dispersions containing birefringent nematic domains in equilibrium with an isotropic phase. The time required for phase separation to occur was shown to depend on the concentration of SWNT and HA, with the attractive interactions between the SWNT and HA shifting the onset of the phase separation toward lower concentration. This phase separation is accompanied by an increase in the dispersion viscosity with this increase qualitatively matching the degree of phase separation. The formation of ordered phases in biological media can offer wide opportunities for processing conducting biomaterials with aligned and oriented domains.     

A Convenient Method for the Preparation of 3 and 3,4 Substituted Thiophenes

Electrochemical polymerization of heterocycles such as pyrrole¹ or thiophene² has been carried out over the past few years to obtain thin films of conducting polymers I. To prepare polythiophenes mono or disubstituted in the 3 and 4 positions by electron-donating groups, we have been looking for an easier preparation of this kind of heterocycle.     

Post-translational modification of Rhodococcus R312 and Comamonas NI1 nitrile hydratases

Nitrile hydratases (NHases) are industrially significant iron- and cobalt-containing enzymes used in the large-scale synthesis of acrylamide. Previous reports have shown that the active site peptides of NHases are post-translationally modified by oxidation of cysteine residues, and that these modifications are essential for catalysis. We report mass spectrometric evidence of the oxidation states of the active site cysteines in the iron coordination spheres of two iron-containing nitrile hydratases, namely R312 NHase from Rhodococcus rhodochrous strain R312 and NI1 NHase from Comamonas testosteroni. At least one of these cysteines is oxidised to a sulfinic acid (SO(2)H) and there is also evidence suggesting an additional oxidation to a sulfenic acid (SOH). This is the first evidence for the presence of these oxidation states for full-length NHases and for Fe-NHases from different microorganisms. The presence of these covalent modifications was confirmed by performing mass spectrometry on the active site peptide of R312 NHase, under native, reduced and carboxymethylated conditions. We also show the nitrosylation of the iron by mass spectrometry, as well as the release of NO by photoirradiation.     

Droplet counter-current chromatography for the preparative isolation of various glycosides

Droplet counter-current chromatography has proven to be an efficient method for separating polar compounds in the range of a few mg to gram quantities, and in this respect is complementary to the popular high-performance liquid chromatography. This is exemplified in the following by the direct obtention of four bioactive saponins in pure form from the crude extract of Hedera helix berries, isolation of an extremely unstable catechin glycoside from Dalbergia nitidula and the separation of flavone glycosides. A rapid thin-layer chromatography method for selecting the solvent system is also described.