The use of DOSY experiments to determine the solution structures of coinage metal pyrazolates: The case of {[3,5-(CF3 )2 Pz]Ag}3.

A series of DOSY experiments have been carried out to determine the solution stoichiometry of silver(I) 3,5-bis (trifluoromethyl)pyrazolate species. This compound exists as a trimer in the solid state (n = 3) but in solutions of chlorinated solvents, the DOSY data suggest the presence of a mixture of solvent stabilized monomer (n = 1) and dimer (n = 2) in equilibrium. Different approximations have been used including the Stokes-Einstein and the Stokes-Einstein-Gierer-Wirtz equations. Some methodological problems are discussed.

Hydrolysis and transgalactosylation catalysed by ß-galactosidase from brush border membrane vesicles isolated from pig small intestine: A study using lactulose and its mixtures with lactose or galactose as substrates.

Enzymatic transgalactosylation, in different concentrated carbohydrate solutions, was investigated using brush border membrane vesicles (BBMV) from the pig small intestine. When lactulose was incubated with BBMV, the hydrolytic activity of the enzyme towards the disaccharide was observed to be very low compared to that towards the lactose, but the linkage specificity ß-(1 â†’ 3), previously observed in lactose solutions, was not significantly affected. As in the case of lactose, lactulose transgalactosylation by BBMV synthesizes the corresponding 3'-galactosyl derivative (ß-Gal-(1 â†’ 3)-ß-Gal-(1 â†’ 4)-ß-Fru). Fructose released during lactulose hydrolysis was found to be good acceptor for the transgalactosylation reaction, giving rise to the synthesis of the disaccharide ß-Gal-(1 â†’ 5)-Fru. When incubating an 80/20 mixture of lactulose/galactose, the presence of galactose did not affect the qualitative composition of the transglycosylated substrate but enhanced the synthesis of ß-Gal-(1 â†’ 5)-Fru and decreased the synthesis of ß-(1 â†’ 3) glycosidic bonds. The marked tendency for synthesizing this linkage indicates that under hydrolytic conditions, ß-Gal-(1 â†’ 3)-Gal- and ß-Gal-(1 â†’ 5)-Fru glycosidic bonds would be preferentially digested.

New polyhydroxylated sterols from Palythoa tuberculosa and their apoptotic activity in cancer cells.

The chemical study on the total extract of the zoanthid Palythoa tuberculosa, collected from the Red Sea, resulted in the isolation of seven polyhydroxylated sterols (1-7), six of which, palysterols A-F (2-7), are new. Their chemical structures were elucidated on the basis of extensive analysis of their 1-, 2D NMR and MS spectroscopic data. This is the first chemical investigation on the species collected from Red Sea. We studied the cytotoxic effects of the total extract and some of the new polyhydroxylated sterols in three human cancer cell lines (MCF-7, HeLa, and HT-29) and one non-cancerous human cell line (KMST-6). Palysterol F (7), in particular, was able to selectively induce high levels of apoptosis (>75%) in breast adenocarcinoma (MCF-7) cells but not HeLa, HT-29 and KMST-6 cells.