Metabolic stability of superoxide adducts derived from newly developed cyclic nitrone spin traps

Reactive oxygen species are by-products of aerobic metabolism involved in the onset and evolution of various pathological conditions. Among them, the superoxide radical is of special interest as the origin of several damaging species such as H2O2, hydroxyl radical, or peroxynitrite (ONOO-). Spin trapping coupled with ESR is a method of choice to characterize these species in chemical and biological systems and the metabolic stability of the spin adducts derived from reaction of superoxide and hydroxyl radicals with nitrones is the main limit to the in vivo application of the method. Recently, new cyclic nitrones bearing a triphenylphosphonium or permethylated β-cyclodextrin moiety have been synthesized and their spin adducts demonstrated increased stability in buffer. In this article, we studied the stability of the superoxide adducts of four new cyclic nitrones in the presence of liver subcellular fractions and biologically relevant reductants using an original setup combining a stopped-flow device and an ESR spectrometer. The kinetics of disappearance of the spin adducts were analyzed using an appropriate simulation program. Our results highlight the interest of the new spin trapping agents CD-DEPMPO and CD-DIPPMPO for specific detection of superoxide with high stability of the superoxide adducts in the presence of liver microsomes. © 2013 Elsevier Inc. All rights reserved

Speeding-up enzyme-catalyzed synthesis of polyamides using omega-amino-alpha-alkoxy-acetate as monomer

International audienceThe design of omega-amino-alpha-alkoxy-acetate as monomer enables to dramatically speed up the formation of polyamides catalyzed by the supported lipase B of Candida antarctica. Only 30 min are needed to reach 93% conversion whereas 240 h are necessary to observe the same level of conversion with a monomer devoided of an oxygen atom in position beta relative to the electrophilic carbonyl group. Yields, Mn, Mw, DPn and PDI reach very good values for an enzymatic synthesis of polyamides. (C) 2013 Elsevier Ltd. All rights reserved

Excess commuting en Île-de-France : une analyse par un modèle de micro-simulation

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CAL-B catalyzed synthesis of chiral polyamides

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Novozym 435-catalyzed synthesis of polyetheramides from amino-esters, or diesters and diamines built on ethylene- and diethylene- glycol moieties

International audienceThe optimization of CAL-B-promoted (Novozym 435) A/B and AA/BB type polymerizations leading topolyetheramides, from amino ethylesters or diethyl esters and diamines based on ethylene- ordiethylene-glycol moieties, is disclosed herein. From these preliminary experiments it became obviousthat it is of prime importance: to avoid the presence of water by carefully drying the enzyme prior to use;to eliminate ethanol from the reaction medium, by working under reduced pressure in order to drive theamidation reaction forward; to select an appropriate high boiling solvent, the best choice being diphenylether. Under such experimental conditions, polyetheramides were obtained in 70e80% yield with anaverage degree of polymerization (DPn) up to 17

Straightforward Access to alpha-Methylamines through Cross-Metathesis

International audienceA two-step procedure involving cross-metathesis and reductive amination enables easy access to alpha-methylamines and alpha,alpha'-dimethyldiamines from a wide variety of terminal olefins

Detection of superoxide production in stimulated and unstimulated living cells using new cyclic nitrone spin traps

International audienceReactive oxygen species (ROS), including superoxide anion and hydrogen peroxide (H2O2), have a diverse array of physiological and pathological effects within living cells depending on the extent, timing, and location of their production. For measuring ROS production in cells, the ESR spin trapping technique using cyclic nitrones distinguishes itself from other methods by its specificity for superoxide and hydroxyl radical. However, several drawbacks, such as the low spin trapping rate and the spontaneous and cell-enhanced decomposition of the spin adducts to ESR-silent products, limit the application of this method to biological systems. Recently, new cyclic nitrones bearing a triphenylphosphonium (Mito-DIPPMPO) or a permethylated β-cyclodextrin moiety (CD-DIPPMPO) have been synthesized and their spin adducts demonstrated increased stability in buffer. In this study, a comparison of the spin trapping efficiency of these new compounds with commonly used cyclic nitrone spin traps, i.e., 5,5-dimethyl-1-pyrroline N-oxide (DMPO), and analogs BMPO, DEPMPO, and DIPPMPO, was performed on RAW 264.7 macrophages stimulated with phorbol 12-myristate 13-acetate. Our results show that Mito-DIPPMPO and CD-DIPPMPO enable a higher detection of superoxide adduct, with a low (if any) amount of hydroxyl adduct. CD-DIPPMPO, especially, appears to be a superior spin trap for extracellular superoxide detection in living macrophages, allowing measurement of superoxide production in unstimulated cells for the first time. The main rationale put forward for this extreme sensitivity is that the extracellular localization of the spin trap prevents the reduction of the spin adducts by ascorbic acid and glutathione within cells