Maghemite nanoparticles bearing di(amidoxime) groups for the extraction of uranium from wastewaters

Polyamidoximes (pAMD) are known to have strong affinities for uranyl cations. Grafting pAMD onto the surface of functionalized maghemite nanoparticles (MNP) leads to a nanomaterial with high capacities in the extraction of uranium from wastewaters by magnetic sedimentation. A diamidoxime (dAMD) specifically synthesized for this purpose showed a strong affinity for uranyl: Ka = 105 M-1 as determined by Isothermal Titration Calorimetry (nano-ITC). The dAMD was grafted onto the surface of MNP and the obtained sorbent (MNP-dAMD) was characterized. The nanohybrids were afterward incubated with different concentrations of uranyl and the solid phase recovered by magnetic separation. This latter was characterized by zeta-potential measurements, X-Ray Photoelectron Spectroscopy (XPS) and X-Ray Fluorescence spectroscopy (XRF), whereas the supernatant was analyzed by Inductively Coupled Plasma coupled to Mass Spectrometry (ICP-MS). All the data fitted the models of Langmuir, Freundlich and Temkin isotherms very well. These isotherms allowed us to evaluate the efficiency of the adsorption of uranium by MNP-dAMD. The saturation sorption capacity (qmax) was determined. It indicates that MNP-dAMD is able to extract up to 120 mg of uranium per gram of sorbent. Spherical aberration (Cs)-corrected High-Resolution Scanning Transmission Electron Microscopy (HRSTEM) confirmed these results and clearly showed that uranium is confined at the surface of the sorbent. Thus, MNP-dAMD presents a strong potential for the extraction of uranium from wastewaters

Chimie des pigments anthocyaniques. 4. Spectre d’absorption UV-visible de la forme chalcone de la glucoside-3 malvidine

Les anthocyanes existent, en milieu aqueux acide, sous plusieurs formes en équilibre : la base quinonique, le cation flavylium, le carbinol et la chalcone. Du tait de sa faible abondance et du fait de la présence des trois autres structures, l'observation spectroscopique de la forme chalcone est diffi- cile. Nous donnons ici une méthode permettant d'obtenir le spectre d’absorption UV-visible de la forme chalcone de la glucoside-3 malvidine. Ce spectre présente des caractéristiques semblables à celles des spectres de chalcones de pigments flavylium, en général d’origine non naturelle. Toutefois, au maximum d’absorption (340-350 nm), la valeur du coefficient d’extinction moléculaire (≈ 10 000 M-1 .cm-1) reste faible devant celles des pigments précités (20 000 à 30 000 M-1.cm-1)

Design and synthesis of 3-isoxazolidone derivatives as new Chlamydia trachomatis inhibitors.

International audienceChlamydia trachomatis (Ct) is a bacterial human pathogen responsible for the development of trachoma, the worldwide infection leading to blindness, and is also a major cause of sexually transmitted diseases. As iron is an essential metabolite for this bacterium, iron depletion presents a promising strategy to limit Ct proliferation. The aim of this study is to synthesize 3-isoxazolidone derivatives bearing known chelating moieties in an attempt to develop new bactericidal anti-Chlamydiaceae molecules. We have investigated the paths by which these new compounds affect Ct serovar L2 development in HeLa cells, in the presence or absence of exogenously added iron. The iron-chelating properties of these molecules were also determined. Our data reveal important bactericidal effects which are distinguishable from those due to iron chelation

Citromycetins and bilains A-C: New aromatic polyketides and diketopiperazines from Australian marine-derived and terrestrial Penicillium spp.

Chemical analysis of an Australian marine-derived isolate of Penicillium bilaii, collected from the Huon estuary, Port Huon, Tasmania, yielded the known fungal aromatic polyketides citromycetin (1) and citromycin (2) together with two dihydro analogues, (-)-2,3-dihydrocitromycetin (3) and (-)-2,3-dihydrocitromycin (4). An Australian terrestrial isolate of Penicillium striatisporum collected near Shalvey, New South Wales, also yielded citromycetin (1), citromycin (2), and the new dihydro analogue (-)-2,3-dihydrocitromycetin (3), together with fulvic acid (5), anhydrofulvic acid (6), and a selection of new methoxylated analogues, 12-methoxycitromycetin (7), 12-methoxycitromycin (8), (-)-12-methoxy2,3-dihydrocitromycetin (9), and 12-methoxyanhydrofulvic acid (10). P. bilaii also yielded the rare siderophore pistillarin (11), the known diketopiperazines cyclo-(L-Phe-L-Pro) (12), cyclo-(L-Pro-L-Tyr) (13), cyclo-(L-Pro-L-Val) (14), and cisbis(methylthio)silvatin (15), and three new diketopiperazines, bilains A-C (16-18). The structures for the Penicillium metabolites 1-18 were assigned by a combination of detailed spectroscopic analysis, including correlation with relevant literature data, chemical derivatization, degradation, and biosynthetic considerations. The citromycin polyketides 2 and 4 and the diketopiperazine 15 were weakly cytotoxic