New physicochemical interpretations for the adsorption of food dyes on chitosan films using statistical physics treatment.

In this work, statistical physics treatment was employed to study the adsorption of food dyes onto chitosan films, in order to obtain new physicochemical interpretations at molecular level. Experimental equilibrium curves were obtained for the adsorption of four dyes (FD&C red 2, FD&C yellow 5, FD&C blue 2, Acid Red 51) at different temperatures (298, 313 and 328 K). A statistical physics formula was used to interpret these curves, and the parameters such as, number of adsorbed dye molecules per site (n), anchorage number (n'), receptor sites density (NM), adsorbed quantity at saturation (N asat), steric hindrance (τ), concentration at half saturation (c1/2) and molar adsorption energy (ΔE(a)) were estimated. The relation of the above mentioned parameters with the chemical structure of the dyes and temperature was evaluated and interpreted.

Interpretation of psychophysics response curves using statistical physics.

Experimental gustatory curves have been fitted for four sugars (sucrose, fructose, glucose and maltitol), using a double layer adsorption model. Three parameters of the model are fitted, namely the number of molecules per site n, the maximum response RM and the concentration at half saturation C1/2. The behaviours of these parameters are discussed in relationship to each molecule's characteristics. Starting from the double layer adsorption model, we determined (in addition) the adsorption energy of each molecule on taste receptor sites. The use of the threshold expression allowed us to gain information about the adsorption occupation rate of a receptor site which fires a minimal response at a gustatory nerve. Finally, by means of this model we could calculate the configurational entropy of the adsorption system, which can describe the order and disorder of the adsorbent surface.

[Solid phase peptide synthesis: interest in the valorization of molecular substances from animal venoms]. / LA SYNTHESE PEPTIDIQUE EN PHASE SOLIDE: INTERET DANS LA VALORISATION DES SUBSTANCES MOLECULAIRES ISSUES DE VENINS ANIMAUX.

Toxins from animal venoms are small peptide molecules able to interact with a wide range of specific cellular targets in order to modulate their activity, which enables them to act in many physiological and pathological processes. Recently, structuralandpharmacologicalstudieshaveshown the involvement of these biological agents in the pathogenesis of many diseases like diabetes, cancer paralysis, autoimmune diseases or neurological disorders. Nevertheless, the only punfication from scorpion venoms of theses peptides still doesn't offer sufficient quantities to allow conducting the pharmacological and structure-function studies. The solid phases peptide synthesis (SPPS) is a methodology that allows us to produce non-limited quantities of structural analogsfrom these peptides-toxins in. In this paper; we will try to highlight the importance of this methodology, and peptide engineering in general, in obtaining peptides of interest. We are also going to elucidate the problems encountered during the chemical synthesis of some betides and explain how to overcome them.

New theoretical expressions for the five adsorption type isotherms classified by BET based on statistical physics treatment.

New theoretical expressions to model the five adsorption isotherm types have been established. Using the grand canonical ensemble in statistical physics, we give an analytical expression to each of five physical adsorption isotherm types classified by Brunauer, Emett, and Teller, often called BET isotherms. The establishment of these expressions is based on statistical physics and theoretical considerations. This method allowed estimation of all the mathematical parameters in the models. The physicochemical parameters intervening in the adsorption process that the models present could be deduced directly from the experimental adsorption isotherms by numerical simulation. We determine the adequate model for each type of isotherm, which fixes by direct numerical simulation the monolayer, multilayer, or condensation character. New equations are discussed and results obtained are verified for experimental data from the literature. The new theoretical expressions that we have proposed, based on statistical physics treatment, are rather powerful to better understand and interpret the various five physical adsorption type isotherms at a microscopic level.