Roussel Uclaf

About: Roussel Uclaf is a based out in . It is known for research contribution in the topics: Alkyl & Alkoxy group. The organization has 1888 authors who have published 2338 publications receiving 36508 citations.

Ketolides lack inducibility properties of MLS(B) resistance phenotype.

Abstract: Ketolides belong to a new class of semi-synthetic 14-membered-ring macrolides, which differ from erythromycin A by having a 3-keto group instead of the neutral sugar L-cladinose. The ability of these molecules and their L-cladinose counterparts to induce MLS B resistance in staphylococci (one strain) and streptococci (two strains) was investigated using a disc agar susceptibility method as well as measuring induction kinetics. All 14- and 15-membered ring macrolides tested showed inducing activity. In contrast, ketolides were clearly unable to induce MLS B resistance, a result consistent with the high in-vitro activity of this new class of antibiotics against erythromycin A-inducible resistant bacteria.

Physical adsorption of gases

Abstract: Some criticisms of the Langmuir and the BET adsorption models are presented which reveal the fallacy of the Langmuir conception of physical adsorption. These errors are corrected and new isotherms for monolayer and multilayer physical adsorption derived. These isotherms are represented by the exponential functions V=V m {1−exp (−a x)} for monolayer adsorption and V=V m {1−exp (−a x)} exp (b x) for multilayer adsorption, where V is the volume adsorbed, Vm the monolayer volume, x the relative pressure of the surrounding gas phase in equilibrium with the adsorbed phase, and a and 6 two constants which describe adsorption in the first and in the second and higher layers, respectively. They are given by a=σ τ p0/√2 π m kT b=σ τ L p0/2 π m kT where σ is the area ascribed to one admolecule, τ and τ L are the average settling time of admolecules in the first and in the second and higher layers, respectively, p 0 the saturation pressure, m the mass of one molecule, and T the absolute temperature.

Purification and properties of a recombinant sulfur analog of murine selenium-glutathione peroxidase

Abstract: We previously constructed plasmids for synthesis of glutathione-peroxidase (GPx) mutants in an Escherichia coli expression system. In these recombinant proteins either cysteine ([Cys]GPx mutant) or serine ([Ser]GPx mutant) were present in place of the active-site selenocysteine (SeCys) of the natural enzyme. We have now investigated GPx activity of [Cys]GPx and [Ser]GPx mutants. Enzyme assays performed on preparations of these partially purified proteins demonstrated that the [Cys]GPx mutant exhibited a significant GPx activity, unlike the [Ser]GPx mutant. Purification of [Cys]GPx was performed in two steps of ion-exchange chromatography giving a 98% homogenous protein in 50% yield. The purified [Cys]GPx protein was shown to be a symmetrical tetramer by the means of gel-filtration HPLC and SDS/PAGE. Two isoelectric points were found (6.8 and 7.2) which may reflect two different oxidation states of the mutant protein. The GPx activity of the [Cys]GPx mutant was optimal at pH 8.5. The [Cys]GPx mutant had a specific activity approximately 1000-fold smaller than that of the natural enzyme, and was very easily inactivated by hydroperoxides. Inhibition of the activity with iodoacetate determined a pKa of 8.3, presumably that of the active-site cysteine. Unlike that of SeGPx, the GPx activity of [Cys]GPx was only slightly inhibited by mercaptosuccinate. We discuss hypothetical mechanistic constraints of either catalytic cycle, which may explain such results.