Monomère

Résumé

En chimie, un monomère est une substance, le plus souvent organique, utilisée dans la synthèse des oligomères et des polymères au cours d'une réaction d'oligomérisation ou de polymérisation. Le mot monomère vient du grec monos, un seul ou une seule, et meros, partie. En biologie, un monomère (ou sous-unité) est l'élément constitutif des protéines multimériques telles l'hémoglobine. L'agencement des monomères les uns par rapport aux autres est décrit par la structure quaternaire de la protéine. Cet article s'intéresse aux monomères selon leur définition en chimie. Fonctionnalité Un monomère peut contenir une ou plusieurs fonctions chimiques susceptibles de participer à la réaction de polymérisation. Chaque groupe fonctionnel d'une molécule de monomère contient un ou plusieurs sites réactifs (ou sites actifs) capables de former une liaison chimique avec une autre molécule de monomère. La fonctionnalité d'un monomère est égale au nombre de sites réactifs que comporte chacune

Source officielle

https://fr.wikipedia.org/wiki/Monom%C3%A8re

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In this course we will study the cell (minimum unit of life) and its components. We will study several key cellular features: Membranes, genomes, channels and receptors. We will apply the laws of physics to develop models to make quantitative and predictive statements.

Introduction à la physique des polymères et aux liens entre structures chimiques et propriétés macroscopiques, avec accent sur la morphologie et le comportement thermomécanique. Méthodes de mise en œuvre, fournissant les bases nécessaires à la sélection des polymères dans un contexte industriel.

This course instructs students in the use of advanced computational models and simulations in cell biology. The importance of dimensionality, symmetry and conservation in models of self-assembly, membranes, and polymer/filament scaling laws reveals how cells exploit these principles in life.

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Modified poly(carboxylate ether)-based superplasticizer for enhanced flowability of calcined clay-limestone-gypsum blended Portland cement

Tunahan Aytas, Aurélie Rosine Favier, Amin Hodaei, Karen Scrivener, Buse Tatli

Supplementary materials that are utilized to replace ordinary Portland cement (OPC) decrease the workability of the cementitious mixtures and superplasticizers are usually added to cement to control their fluidity. In general, current superplasticizers are solely optimized for single component systems such as OPC. Here, we report the performance of a series of a modified poly(carboxylate ether)-based superplasticizers (PCEs) in a ternary OPC-calcined clay-limestone blend. We have utilized: i) a co-monomer with high ionic character, 2-acrylamido-2-methylpropane sulfonic acid (AMPS) to be incorporated into the acrylic acid backbone of PCEs and ii) low density of polyethylene glycol (PEG) grafted chains < 0.01 mol/mol. The optimized polymer does not intercalate into the layered structure of calcined clay and preserves its steric size in the presence of high concentration of sulfate ions.

Elsevier2017

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Secondary transporters exist as monomers, dimers or higher state oligomers. The significance of the oligomeric state is only partially understood. Here, the significance of the trimeric state of the L-carnitine/gamma-butyrobetaine antiporter CaiT of Escherichia coli was investigated. Amino acids important for trimer stability were identified and experimentally verified. Among others, CaiT-D288A and -D288R proved to be mostly monomeric in detergent solution and after reconstitution into proteoliposomes, as shown by blue native gel electrophoresis, gel filtration, and determination of intermolecular distances. CaiT-D288A was fully functional with kinetic parameters similar to the trimeric wild-type. Significant differences in amount and stability in the cell membrane between monomeric and trimeric CaiT were not observed. Contrary to trimeric CaiT, addition of substrate had no or only a minor effect on the tryptophan fluorescence of monomeric CaiT. The results suggest that physical contacts between protomers are important for the substrate-induced changes in protein fluorescence and the underlying conformational alterations.

2019

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Partial oxidation of toluene to benzaldehyde and benzoic acid over model vanadia/titania catalysts: Role of vanadia species

Lioubov Kiwi, Fabio Rainone

Pure and K-doped vanadia/titania prepared by different methods have been studied in order to elucidate the role of vanadia species (monomeric, polymeric, bulk) in catalytic toluene partial oxidation. The ratio of different vanadia species was controlled by treating the catalysts in diluted HNO3, which removes bulk vanadia and polymeric vanadia species, but not the monomeric ones, as was shown by FT-Raman spectroscopy and TPR in H2. Monolayer vanadia species (monomeric and polymeric) are responsible for the catalytic activity and selectivity to benzaldehyde and benzoic acid independently on the catalyst preparation method. Bulk V2O5 and TiO2 are considerably less active. Therefore, an increase of the vanadium concentration in the samples above the monolayer coverage results in a decrease of the specific rate in toluene oxidation due to the partial blockage of active monolayer species by bulk crystalline V2O5. Potassium diminishes the catalyst acidity resulting in a decrease of the total rate of toluene oxidation and suppression of deactivation. Deactivation due to coking is probably related to the Brønsted acid sites associated with the bridging oxygen in the polymeric species and bulk V2O5. Doping by K diminishes the amount of active monolayer vanadia leading to the formation of non-active K-doped monomeric vanadia species and KVO3.

2004

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