Roles of divalent cations and pH in mechanism of action of nitroxoline against Escherichia coli strains.

The antibacterial activity of nitroxoline (NIT), an antibiotic used in the treatment of acute or recurrent urinary tract infections caused by Escherichia coli, is decreased in the presence of Mg2+ and Mn2+ but not Ca2+. In order to elucidate the interaction between this drug and the divalent cations, spectrophotometric studies based on the natural absorption of the nitroxoline moiety were conducted. In the presence of the divalent metal ions, a shift in the NIT A448 suggested the formation of drug-ion complexes, for which the stability followed the order Mn2+ > Mg2+ > Ca2+. A clear correlation was found between the chelating property and antibacterial activity of NIT; both were pH dependent. A convenient colorimetric method for the determination of NIT uptake by bacterial cells was also developed. Uptake was energy independent and showed biphasic kinetics: a rapid association with cells and then a slower increase in cell-associated NIT which reached a plateau. NIT uptake was reduced in the presence of magnesium. The implications of metal ion complexation and pH on the clinical efficacy of NIT are discussed

Some Insights About 1,6-Diphenyl-1,3,5-hexatriene-Lipid Supramolecular Assemblies by Steady-State Fluorescence Measurements

International audienceDiphenyl-1,3,5-hexatriene (DPH) is the most widely proposed molecular probe for the post-column fluorescence derivatization of lipids after liquid chromatography separation. This kind of detection consists of a supramolecular combination of DPH and eluted lipids. The detection is optimally performed in a mainly aqueous environment (over 80% v/v) because the weak fluorescence of DPH in water is drastically enhanced upon formation of supramolecular assemblies with lipids. In the present study, and in order to obtain better spectroscopic insights into the nature of these supramolecular assemblies, two different lipids were tested, 1,2,3tridodecanoylglycerol (LLL) as a model triglyceride (nonpolar lipid) and dimyristoylphosphatidylcholine (DMPC) as a model phosphatidylcholine (charged amphiphilic lipid). Stoichiometry and association constants were determined on the basis of the variation of fluorescence intensity in the presence of various concentrations of lipids. LLL 60-DPH 2 and DMPC 200-DPH 2 complexes were identified with association constants as high as K 2 ¼ (5.8 6 0.5) 3 10 13 M À2 and (17.3 6 2.0) 3 10 13 M À2 for LLL and DMPC, respectively. The fluorescence intensity of DPH in the presence of LLL is greater than in the presence of DMPC. An attempt to characterize the insertion mode of DPH in the lipidic supramolecular assemblies is also made

Intérêt et limites de la détermination de l’activité enzymatique de l’α-galactosidase A dans les populations à risque pour la maladie de Fabry

La prévalence de la maladie de Fabry est très faible dans la population générale. Toutefois, la détermination de l’activité de l’α-galactosidase A présente un intérêt dans les populations à risqué

Quantification et spéciation du globotriaosylcéramide

Au cours de la maladie de Fabry, le déficit enα-galactosidase A entraîne une accumulation de globotriaosylcéramide. La quantification et la spéciation de ce lipide peuvent être réaliséespar différentes méthodes (en particulier par spectrométrie de masse en tandem couplée à une technique séparative) qui sont décrites etanalysée

Avancées récentes dans le dépistage de la maladie de Fabry pour les populations à risque

Une étude portant sur 51 sujets, dont 15 hommeshémizygotes 12 femmes hétérozygotes et 24 témoins, décrit une méthode de dépistage par dosage de l’α-galactosidase A sur goutte de sang recueillie sur papier filtre, et son intérêt dans les populations à risque de maladie de Fabr

Diprotonation process of meso-tetraphenylporphyrin derivatives designed for Photodynamic Therapy of cancers: From Multivariate Curve Resolution to predictive QSPR modeling

International audienc

Meso-tetraphenyl porphyrin derivatives: The effect of structural modifications on binding to DMPC liposomes and albumin

International audienc

Conséquences budgétaires de l’innovation médicamenteuse à l’hôpital : exemple de la maladie de Fabry

National audienc