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See detailContribution à l'étude des propriétés tensioactives et membranaires d'esters dérivés de la glycine bétaïne
Nsimba Zakanda, Francis ULg

Doctoral thesis (2012)

The objective of this doctoral research is to contribute to the study of surface active and membrane properties of esters derived from glycine betaine. In this context, esters of glycine betaine ... [more ▼]

The objective of this doctoral research is to contribute to the study of surface active and membrane properties of esters derived from glycine betaine. In this context, esters of glycine betaine (alkylbétaïnate chlorides: CnBC, n = 10-16) were obtained using a new synthetic methodology. Glycine betaine (activated by thionyl chloride) and the primary fatty alcohols were used as basic raw materials for the chemical synthesis of CnBC. Some parameters to optimize the synthesis were studied, such as the nature of the organic solvent, the temperature, the molar ratio of reactants and the concentration of the latter in the reaction medium. Next, the surface active and membrane properties of CnBC were characterized using several instrumental techniques such as Langmuir film balance, isothermal titration calorimetry, fluorescence spectrometry and zeta potential and particle size measurements. Hexadécylbétaïnate chloride (C16BC) was synthesized with better performance under the following conditions: absence of a catalyst/base, a solvent of medium polarity (2-methyl-2-butanol), a temperature of 45°C, a molar ratio of betainyl chloride/1-hexadecanol of 3/1 and a concentration of reactants of 0.132 mol/L. Decylbetainate chloride (C10BC) dodecylbetainate chloride (C12BC) and tetradecylbetainate chloride (C14BC) were obtained using the optimal conditions for the synthesis of C16BC. Concerning the interfacial organization of CnBC, C10BC and C12BC did not form insoluble monolayers at the air-water at 20°C compared to their counterparts, C14BC and C16BC. The study of the monolayer of C16BC in various conditions of the aqueous subphase showed that the pH and monovalent anions (OHˉ, Brˉ, NO3ˉ, ClO4ˉ) did not influence the behavior of the monolayer compared to that in water with Clˉ as counterion while the temperature beyond 25°C, the divalent anions (HPO42-, SO42-) and the ionic strength of sodium sulfate (Na2SO4) affected it in term of interfacial area occupation of the molecules. Interactions between CnBC and model membranes have shown that in water, CnBC, regardless of the length of the alkyl chain, have highly penetreted into the negatively charged lipid monolayers (dipalmitoylphosphatidylserine and dipalmitoylphosphatidic acid), whereas their penetration was average and low into monolayers formed by lipids with small polar head (dipalmitoylphosphatidylethanolamine and cholesterol, CHOL) and lipid with large polar head (palmitoyloleoylphosphatidylcholine, POPC), respectively. In salted buffer, the adsorption of C16BC at the air-water interface and onto the surfaces of the lipid monolayers was instantaneous, and in all cases, the penetrating power was above the presumed pressure of biological membranes. C16BC formed miscible and stable mixtures with POPC and sphingomyelin while an almost ideal behavior was observed for its mixtures with CHOL. An affinity of C16BC for the membrane bilayer containing CHOL was also observed. The adsorption of CnBC onto the surfaces of bilayers was alkyl chain-dependent. C10BC, C14BC and C16BC did not significantly perturbed membranes even at high surfactant concnetrations compared to C12BC that has highly perturbed membranes without solubilizing them. In all cases, particles of positive charge and larger than those of membrane bilayers prepared were formed in the presence of high amounts of CnBC. [less ▲]

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See detailPenetration behaviour of alkylbetainate chlorides into lipid monolayers
Nsimba Zakanda, Francis ULg; Nott, Katherine ULg; Paquot, Michel ULg et al

in Colloids and Surfaces B : Biointerfaces (2011), 86

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See detailAlkylbetainate chlorides: Synthesis and behavior of monolayers at the air-water interface
Nsimba Zakanda, Francis ULg; Laurent, Pascal ULg; Paquot, Michel ULg et al

in Thin Solid Films (2011), 520

In this study, cationic alkylbetainate chloride surfactants (CnBC, n = 10–16) are synthesized using more environment-friendly reagents (glycine betaine, thionyl chloride and primary alcohols) than in ... [more ▼]

In this study, cationic alkylbetainate chloride surfactants (CnBC, n = 10–16) are synthesized using more environment-friendly reagents (glycine betaine, thionyl chloride and primary alcohols) than in previous works (chloroacetyl chloride, trimethylamine and primary alcohols). The interfacial behavior of the CnBC monolayers is studied onto aqueous subphases at 20 °C using the Langmuir through technique. Different experimental conditions including pH, temperature, sodium salts and Na2SO4 ionic strength are investigated. The results obtained have shown that the CnBC with a hydrocarbon chain length ≥ 14 are able to form insoluble monolayers. The C16BC monolayer stability checked by the compression–expansion cycles has shown a superimposition of isotherms in the whole liquid-condensed region and an irreversible rearrangement of the molecules at high compression. The C16BC monolayer is not influenced by the pH and the presence of monovalent anions but it is influenced by the temperature, the divalent anions and the ionic strength. It has exhibited a great stability whatever the experimental conditions. [less ▲]

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