Un modèle de l'activité catalytique de métalloenzymes : le système hydroxyméthyl-2 benzimidazole-zn

On décrit les premiers résultats sur l'activité estérolytique de nouveaux modèles de métalloenzymes associant une fonction alcool à un cycle benzimidazole. L'étude cinétique de l’action de l'hydroxyméthyl-2 benzimidazole en présence d'ions Zn++ sur l'hydrolyse du picolinate de p-nitrophényle montre un effet catalytique important attribué à la formation préliminaire d’un complexe catalyseur-Zn++ et permet de proposer un mécanisme de type enzymatique

SYNTHESE DE NOUVEAUX COPOLYMERES AMPHIPHILES CATIONIQUES A BLOCS PAR VOIE RADICALAIRE CONTROLEE ET EXAMEN DE LEURS PROPRIETES PHYSICO-CHIMIQUES EN SOLUTION AQUEUSE

NANCY/VANDOEUVRE-INPL (545472102) / SudocSudocFranceF

Activité estérolytique de composés associant une fonction thiol et une base hétérocyclique. Exemples de processus bifonctionnel

On décrit la synthèse de 19 composés associant une fonction thiol à une base hétérocyclique (benzimidazole, pyridine, thiazole) et l'étude de leur activité estérolytique vis à vis de l'acétate de p-nitrophényle, comparativement à celles des thiols simples monofonctionnels. L'influence des substituants et de la nature de l'hétérocycle montre que l'apparition d'un effet coopératif dépend de la valeur relative des deux pKa(pKSH et pKa du site basique) ainsi que de la possibilité d'échange protonique par l'intermédiaire de l'hétérocycle. Plusieurs exemples de processus bifonctionnel par assistance basique sur le groupement thiol neutre apparaissent dans le cas des benzimidazolylméthanethiols

Determination of fluid viscoelastic properties using resonant microcantilever

International audienceThe dynamic characteristics of a microcantilever depend on the fluid in which the beam is immersed. In this paper, the analysis of the frequency response of microcantilevers immersed either in viscous or viscoelastic fluid is performed in order to determine if this vibrating device could be used as ‘microrheometer'

Cellulose acetate graft copolymers with nano-structured architectures: Synthesis and characterization

International audienceCellulose acetate is a very good film-forming polymer with major applications in cigarette filters, photographic films, cosmetics and pharmaceutics formulations and membrane separation processes. Nevertheless, its rigidity and relative hydrophobic character can be limiting drawbacks for some applications. In this work, new cellulose acetate materials with highly flexible and hydrophilic grafts were obtained with different hydrophilic/hydrophobic balances. Cellulose acetate was grafted with methyl diethylene glycol methacrylate (MDEGMA) from brominated macroinitiators by atom transfer radical polymerization (ATRP) in two steps. The first step consisted of introducing ATRP initiator groups on cellulose acetate by reacting hydroxyl side groups with 2-bromoisobutyryl bromide. A preliminary study was then carried out to determine the experimental conditions for the controlled ATRP of MDEGMA homopolymerization in a solvent (cyclopentanone) compatible with cellulose acetate grafting. In these conditions, the MDEGMA homopolymerization followed Hanns Fischer's kinetics model accounting for the radical persistent effect. The ATRP grafting was then investigated for two cellulose acetate macroinitiators differing in the number of their ATRP initiator groups. Two families of graft copolymers with nano-structured architectures were obtained. The first family corresponded to copolymers with a high number of short grafts. The copolymers of the second family had almost the same graft weight fractions but a small number of long grafts. The morphology of the graft copolymers was then investigated by synchrotron X-ray scattering. The most informative results showed that the phase segregation depended upon the number and length of the poly(MDEGMA) grafts. The copolymer with 44 wt.% of long grafts showed a segregated morphology of nano-domains with sharp interfaces and a radius of gyration of 11.5 nm (from Guinier's law). These cellulose acetate copolymers eventually led to strong films with potential applications in membrane separations

Estimation of Unbound Carboplatin Clearance From Total Plasma Concentrations as a Means of Facilitating Therapeutic Drug Monitoring

International audienc