ESR study of the spin adducts of three analogues of DEPMPO substituted at C-4 or C-3

In the research program of some new derivatives of spin-trap DEPMPO (5-diethoxyphosphoryl-5-methyl-1-pyrroline-N-oxide) leading to various radical adducts with photogenic ESR signals, three phosphorylated pyrroline-N-oxides were studied in spin trapping. These nitrones were proved to trap a variety of free radicals to afford adducts presenting characteristic ESR signals enabling unambiguous identification of the radical species trapped. From the general patterns of the signals, the adduct geometries were determined. Two of the nitrones bore a hydroxylmethyl substituent (HM) on the pyrroline ring, either at C-3 or at C-4. The two diastereoisomers of nitrone 4-HMDEPMPO, whose synthesis has been already described, were separately studied. The isomer (4R*,5R*) of 4-HMDEPMPO afforded stereoselectively, with superoxide or peroxyl radicals, trans adducts versus the phosphoryl group, however, they formed two rotamer sets in chemical exchange. In comparison with DEPMPO adducts, the exchanges rates of the conformer sets of 4-HMcisDEPMPO-OOH and 4-HMcisDEPMPO-(OOBu)-Bu-t were 9-fold or 2-fold smaller respectively. The eight-line signals of theses adducts were easily recognisable. The trapping of the same radicals with the other diastereoisomer (4S*,5R*)-4-HMDEPMPO or with (3S*,5R*)-3-HMDEPMPO, obtained via oxidation of a phosphorylated pyrroline, led to more complicated spectra owing to the formation of diastereoisomer adducts. The signal of each diastereoisomer adduct was simulated with two species in conformational exchange. In comparison with DEPMPO, the cis-C-4-substitution was proved to slow by 26-fold the exchange rate between the two rotamer sets of the trans superoxide adduct versus the phosphoryl group. The trans-C-3-substitution was proved to slow by 18-fold, at 223 K, the exchange rate between the two rotamer sets of the trans terbutylperoxyl adduct. The last nitrone, a bicyclic one, named MEOOPPO (6a-methyl-(6-ethoxy-5-oxa-6-oxaphospholan-6-yl)-1-pyrroline-N-oxide) was obtained directly from (4R*,5R*)-4-HMDEPMPO in basic conditions. Superoxide with the rigid MEOOPPO reacts exclusively in trans addition versus the phosphoryl group, however, the adduct obtained in aqueous buffer was not very persistent and the nitrone was partially degraded during 30 min storage. For every nitrone, the hydroxyl radical was not added stereoselectively on one ring face and some diasteroisomer adducts were obtained

DEPMPO: an efficient tool for the coupled ESR-spin trapping of alkylperoxyl radicals in water

International audiencePeroxidation is an important process both in chemistry and biology, and peroxyl radicals play a crucial role in various pathological situations involving lipid and protein peroxidation. A few secondary and tertiary peroxyl radicals can be detected directly by Electron Spin Resonance (ESR). However, primary and secondary alkylperoxyl radicals have extremely short lifetimes and their direct observation is impossible in biological samples. DMPO has been used to trap alkylperoxyl radicals generated in biological systems and the characterization of DMPO-alkylperoxyl spin adducts has been claimed by different authors. However, it was then clearly shown that all the assignments made previously to DMPO-OOR adducts were actually due to DMPO-OR adducts. We have investigated the potential of DEPMPO to characterize the formation of alkylperoxyl radicals in biological milieu. Various DEPMPO-OOR (R = Me, primary or secondary alkyl group) spin adducts were unambiguously characterized and the formation of DEPMPO-OOCH3 was clearly established during the reaction of tert-butylhydroperoxide with chloroperoxidase and cytochrome c

Design of New Derivatives of Nitrone DEPMPO Functionalized at C-4 for Further Specific Applications in Superoxide Radical Detection

International audienceA general synthetic route to prepare derivatives of the DEPMPO nitrone (5-diethoxyphosphoryl-5-methyl-1-pyrroline-N-oxide) functionalized at C-4 was established via the synthesis of 4-HMDEPMPO nitrone (5-diethoxyphosphoryl-4-hydroxymethyl-5-methyl-1-pyrroline-N-oxide) that was obtained from reduction of the nitro compound 1. (4R*,5S*)-4-HMDEPMPO was successfully separated from its minor diastereoisomer and could be used to generate various substituted analogues. Among them, 4-NHSDEPMPO, 5-diethoxyphosphoryl-4-succinimidyloxycarbonyloxymethyl-5-methyl-1-pyrroline-N-oxide, constitutes a NH2-reactive precursor for further conjugation to relevant moieties such as targeting groups, labels, or drugs. From 4-NHSDEPMPO, a biotinylated nitrone was synthesized offering new perspectives for targeted delivery applications. A short study of the trapping behaviors of the (4R*,5S*)-isomer of these 4-HMDEPMPO analogues proved that they are as good as DEPMPO for detecting superoxide. For each isomer, only one diastereoisomer adduct was obtained, resulting from the addition of superoxide on the less hindered face of the nitrone, that is, trans to the phosphoryl group and the C-4 substituent. From spectra simulation and experiments in various solvents, we proved that ESR patterns of each adduct corresponded to the superimposed signals of two sets of conformers in a sufficiently slow chemical exchange to induce a widening and a dissymmetry of some of the signal lines. This phenomenon was drastically reduced when compared with that observed for DEPMPO superoxide and attributed to a similar chemical exchange, and it did not hamper spectrum assignment. Determination of the decay rate of the superoxide adduct of (4R*,5S*)-4-HMDEPMPO proved that it has a 25% longer half-life time than the superoxide adduct of DEPMPO

Isolation of an Anti-Tumour Disintegrin: Dabmaurin-1, a Peptide Lebein-1-Like, from Daboia mauritanica Venom.

International audienceIn the soft treatment of cancer tumours, consequent downregulation of the malignant tissue angiogenesis constitutes an efficient way to stifle tumour development and metastasis spreading. As angiogenesis requires integrin-promoting endothelial cell adhesion, migration, and vessel tube formation, integrins represent potential targets of new therapeutic anti-angiogenic agents. Our work is a contribution to the research of such therapeutic disintegrins in animal venoms. We report isolation of one peptide, named Dabmaurin-1, from the hemotoxic venom of snake Daboia mauritanica, and we evaluate its potential anti-tumour activity through in vitro inhibition of the human vascular endothelial cell HMECs functions involved in tumour angiogenesis. Dabmaurin-1 altered, in a dose-dependent manner, without any significant cytotoxicity, HMEC proliferation, adhesion, and their mesenchymal migration onto various extracellular matrix proteins, as well as formation of capillary-tube mimics on MatrigelTM. Via experiments involving HMEC or specific cancers cells integrins, we demonstrated that the above Dabmaurin-1 effects are possibly due to some anti-integrin properties. Dabmaurin-1 was demonstrated to recognize a broad panel of prooncogenic integrins (αvβ6, αvβ3 or αvβ5) and/or particularly involved in control of angiogenesis α5β1, α6β4, αvβ3 or αvβ5). Furthermore, mass spectrometry and partial N-terminal sequencing of this peptide revealed, it is close to Lebein-1, a known anti-β1 disintegrin from Macrovipera lebetina venom. Therefore, our results show that if Dabmaurin-1 exhibits in vitro apparent anti-angiogenic effects at concentrations lower than 30 nM, it is likely because it acts as an anti-tumour disintegrin

La démocratie à l'épreuve de l'épidémie

SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Mises en récit d’innovations

L’enjeu du dossier est de cerner les liens qui unissent le récit à l’innovation. L’innovation comme le récit ont le vent en poupe, la première car elle apparaît comme une réponse aux grands défis contemporains, le second car il serait la solution à de nombreux problèmes de communication et permettrait de toucher plus directement un public, de le convaincre et de l’impliquer. Sans surprise, ils font l’objet d’une abondante littérature en sciences humaines et sociales, dans le champ de l’économie, de la gestion, des sciences de la communication ou des sciences politiques. L’objectif du dossier est de décrire et comprendre ces liens, leurs fonctions et d’en saisir la variété et la richesse