26 research outputs found
Electrochemical behaviour of N-acetyl-l-cysteine on gold electrode—A tentative reaction mechanism
The electrochemical behaviour of N-acetyl-l-cysteine (NAC) has been investigated by linear and cyclic voltammetry on gold electrode at room temperature. The results showed two oxidation peaks under acid and neutral conditions and only one in basic medium. For each oxidation, as many electron was exchanged as proton. The influence of both the concentration and the potential scan rate on the peak currents highlighted a diffusion-controlled phenomenon for the first peak and an adsorption-limited reaction rate for the second one. The diffusion coefficient of NAC in solution and the surface concentration of the adsorbed species at pH 3 and 7 were close to 2 × 10−4 to 2 × 10−5 cm2 s−1 and 6 × 10−9 to 6 × 10−10 mol cm−2, respectively. Film transfer experiments resulted in an irreversible adsorption of NAC on gold electrode, and the formation of a self-assembled monolayer (SAM)
Antiprotozoal glutathione derivatives with flagellar membrane binding activity against T. brucei rhodesiense.
A new series of N-substituted S-(2,4-dinitrophenyl)glutathione dibutyl diesters were synthesized to improve in vitro anti-protozoal activity against the pathogenic parasites Trypanosoma brucei rhodesiense, Trypanosoma cruzi and Leishmania donovani. The results obtained indicate that N-substituents enhance the inhibitory properties of glutathione diesters whilst showing reduced toxicity against KB cells as in the cases of compounds 5, 9, 10, 16, 18 and 19. We suggest that the interaction of N-substituted S-(2,4-dinitrophenyl) glutathione dibutyl diesters with T. b. brucei occurs mainly by weak hydrophobic interactions such as London and van der Waals forces. A QSAR study indicated that the inhibitory activity of the peptide is associated negatively with the average number of C atoms, NC and positively to SZX, the ZX shadow a geometric descriptor related to molecular size and orientation of the compound. HPLC-UV studies in conjunction with optical microscopy indicate that the observed selectivity of inhibition of these compounds against bloodstream form T. b. brucei parasites in comparison to L. donovani under the same conditions is due to intracellular uptake via endocytosis in the flagellar pocket
Étude sur l'évolution de l'emploi du subjonctif dans la littérature du XXe siècle : P. Morand, B. Vian, E.-E. Schmitt
Nous avons souhaité mener une démonstration sur l'évolution de l'emploi du subjonctif dans la littérature du XXe siècle, en posant les bases de notre réflexion sur une question simple en apparence, ardue en réalité : qu'est-ce que le subjonctif ? Nous n'avons pas eu la prétention de vouloir y répondre, mais bien plutôt d'esquisser des pistes de réflexion, en confrontant les points de vue de ceux qui font la langue française : les grammaires pour l'aspect morphosyntaxique, ainsi que différents linguistes et, à travers eux, différentes écoles linguistiques, démontrant, par la multiplicité de leurs théories sur le subjonctif, que ce mode pose problème : ses mécanismes de fonctionnement, variables, instables même, rendent extrêmement difficile une définition exhaustive et unanime. Au-delà de la seule linguistique, il nous a paru intéressant d'élargir notre réflexion en y intégrant une dimension à la fois philosophique, avec Humboldt et Whorf-Sapir, et sociologique, avec Millet et Orsenna, désireux de protéger langue française et subjonctif (l'une étant indissociable de l'autre), afin de mieux comprendre les valeurs dont ce mode est porteur, et d'ouvrir le champ des possibles réponses à une explication de son déclin. Déclin attesté, d'ailleurs, ou simple intuition ? Cette interrogation nous a poussés à mettre en perspective trois auteurs de langue française, représentatifs de trois grandes époques du XXe siècle : P. Morand, B. Vian et E.-E. Schmitt dont l'étude a pu montrer que si évolution il y avait, elle n'atteignait pas encore, du moins à l'écrit, un seuil critique. Il semblerait qu'une étude sur l'évolution du subjonctif à l'oral apporterait certainement des réponses bien plus tranchées, mais pour l'heure, la conclusion à laquelle nous aboutissons est la suivante : certes, le français a évolué en parallèle avec une évolution des mentalités qui a affecté la langue, surtout orale pour le moment ; pourtant l'écrit, et la littérature notamment, bien que touchés par des incursions de la langue courante, résistent encore quelque peu
Glutathione Derivatives Active against Trypanosoma brucei rhodesiense and T. brucei brucei In Vitro
Diesters based on N-benzyloxycarbonyl-S-(2,4-dinitrophenyl) GSH (CBzGSDNP) containing linear alcohols 3 to 9, branched alcohols 10 to 20, or heteroatom linear alcohols 21 to 25, were investigated as in vitro inhibitors of pathogenic parasites. Diesters 3 to 25 were better inhibitors of Trypanosoma brucei rhodesiense than of T. brucei brucei and had low cytotoxicities. The most active compound had a 50% effective dose (ED(50)) of 0.2 μM. A quantitative structure activity regression equation relating the log (1/ED(50)) versus the hydrophobicity parameter (log P), Taft's steric parameter (E(s)), molecular weight (MW), and the WienI descriptor (W) was determined, and the species difference was found to be related to membrane penetration and steric effects
The importance of log P on the Antiparasitic Activity of Glutathione Derivatives in vitro
Structure−Activity Study on the in Vitro Antiprotozoal Activity of Glutathione Derivatives
Structural similitudes between cytotoxic antiestrogen-binding site (AEBS) ligands and cytotoxic sigma receptor ligands. Evidence for a relationship between cytotoxicity and affinity for AEBS or sigma-2 receptor but not for sigma-1 receptor.
1-Benzyl-4-(N-2-pyrrolidinylethoxy)benzene (PBPE) is a cytotoxic derivative of the antitumoral drug tamoxifen. PBPE binds with high-affinity and specificity to the microsomal antiestrogen-binding site (AEBS). PBPE, as well as some other high-affinity AEBS ligands, shares structural features with high-affinity and selective sigma receptor ligands in the N-(arylethyl)-N-alkyl-2-(1-pyrrolidinyl)ethylamine class, such as BD1008, which are cytotoxic against tumoral cells. Based on these structural and pharmacological similitudes, we set out to examine whether AEBS and sigma receptors could be related binding sites. We showed that BD1008 had a high affinity for AEBS. However, prototypical sigma receptor ligands were very low-affinity competitors on AEBS. Surprisingly, AEBS ligands displayed a high affinity for sigma-1 and sigma-2 receptor subtypes, showing that AEBS and sigma receptor-binding sites were not mutually exchangeable. Moreover, phenytoin, which is an allosteric modulator of sigma-1 receptor, was a competitive inhibitor of [3H]tamoxifen on AEBS. These results suggest that the tamoxifen-binding site on AEBS and the sigma ligand-binding site on sigma receptors were not identical but related entities. We also showed here that the high-affinity and specific AEBS ligands also bound sigma receptors with high affinity. Moreover, the compounds that were capable of displacing tamoxifen from AEBS were cytotoxic against tumoral cells but not against the AEBS-deficient cell line Rtx-6. These results confirm that AEBS and sigma receptors might belong to the same family of proteins, and that the tamoxifen-binding site might be involved in the cytotoxicity of AEBS ligands and some classes of sigma compounds
Programa Pensamiento CrÃtico. 80º aniversario del nacimiento del Che Guevara. Parte 1.
Programa Pensamiento CrÃtico. 80º aniversario del nacimiento del Che Guevara. Con la palabra de Miguel Barnet, escritor cubano. Parte 01. Programa 17 de junio
Programa Pensamiento CrÃtico. Unión de Asambleas Ciudadanas. Parte 1
Programa Pensamiento CrÃtico. Unión de Asambleas Ciudadanas. Parte 1. Programa 04 de noviembre
Programa Pensamiento CrÃtico. Coyuntura boliviana antes del referéndum autonomista.
Programa Pensamiento CrÃtico. Diálogo con Pablo Stefanoni (Bolivia) y Julio Salazar (dirigente cocalero) sobre la coyuntura boliviana antes del referéndum autonomista. Programa 29 de abril