The point of zero charge of hydrous RuO2

Hydrous RuO2 has been prepared by alkaline fusion of Ru+KNO3+ KOH and successive decomposition of the ruthenate and perruthenate. The product has been analyzed by thermogravimetric analysis, differential thermal analysis, X-ray diffraction and scanning electron microscopy. Aqueous suspensions of samples of the hydrous oxide calcined at various temperatures between 300 and 500\ub0C have been titrated potentiometrically to determine the point of zero charge. The results have been compared with commercial RuO2\ub7xH2O. The two oxides have been found to differ in composition, structure, morphology and acid-base properties. In particular, hydrous RuO2 contains chemically bound water besides physically bound water, which is the only water present in the commercial sample. The dependence of the point of zero charge of the hydrous RuO2 on calcination temperature follows the same pattern as RuO2 obtained by thermal decomposition of RuCl3, while the behaviour of the commercial sample diverges below the temperature where the chemically bound water is lost by the hydrous RuO2. \ua9 1989

Benzothiadiazole (BTH) activates sterol pathway and affects vitamin D3 metabolism in Solanum malacoxylon cell cultures

Benzo-(1,2,3)-thiadiazole-7-carbothioic acid S-methyl ester (BTH), a particularly efficient inducer of systemic acquired resistance (SAR), was developed as an immunizing agent to sensitize various crop species against pathogen infections. Recent works highlighted its activating effect on different metabolic pathways, concerning both primary and secondary metabolites. In this study, we investigated the effect of BTH treatment on sterol levels and vitamin D-3 metabolism in Solanum malacoxylon cultures. Calli of S. malacoxylon were incubated in Gamborg B5 liquid medium alone or added with 50 mu M BTH for different times (one, two or three cycles of light). Histocytochemical investigations performed on our experimental system using 3,3'-diaminobenzidine (DAB) for hydrogen peroxide (H2O2) detection and phloroglucinol for lignin staining showed that BTH causes H2O2 accumulation and lignin deposition in treated calli. Gas chromatographic analysis of principal cell membrane sterols (beta-sitosterol, campesterol, stigmasterol) showed that BTH transiently increases their cellular levels. Callus cultures were found to contain also cholesterol, 7-dehydrocholesterol, the putative precursor of vitamin D-3, and the hydroxylated metabolites 25-hydroxyvitamin D-3 [25(OH)D-3] and 1 alpha,25-dihydroxyvitamin D-3 [1 alpha,25(OH)(2)D-3]. BTH treatment enhanced 7-dehydrocholesterol while reduced cholesterol. HPLC analysis of sample extracts showed that BTH does not affect the cell content of vitamin D3, though results of ELISA tests highlighted that this elicitor moderately enhances the levels of 25(OH)D-3 and 1 alpha,25(OH)(2)D-3 metabolites. In conclusion, BTH treatment not only causes cell wall strengthening, a typical plant defence response, as just described in other experimental models, but in the same time increases the cellular level of the main sterols and 7-dehydrocholesterol

Inhibition of DC-SIGN-mediated HIV infection by a linear trimannoside mimic in a tetravalent presentation

HIV infection is pandemic in humans and is responsible for millions of deaths every year. The discovery of new cellular targets that can be used to prevent the infection process represents a new opportunity for developing more effective antiviral drugs. In this context, dendritic cell-specific ICAM-3 grabbing non-integrin (DC-SIGN), a lectin expressed at the surface of immature dendritic cells and involved in the initial stages of HIV infection, is a promising therapeutic target. Herein we show the ability of a new tetravalent dendron containing four copies of a linear trimannoside mimic to inhibit the trans HIV infection process of CD4+ T lymphocytes at low micromolar range. This compound presents a high solubility in physiological media, a neglectable cytotoxicity, and a long-lasting effect and is based on carbohydrate-mimic units. Notably, the HIV antiviral activity is independent of viral tropism (X4 or R5). The formulation of this compound as a gel could allow its use as topical microbicide