Removal of textile pollutants from aqueous medium using biosynthesized CuO nanoparticles: Theoretical comparative investigation via analytical model.

The work deals with the removal of two dyes, namely methylene blue (MB) and methyl orange (MO), from polluted water by adsorption onto CuO nanoparticles synthesized with a green synthesis procedure, starting from plant resources. Adsorption isotherms are determined at different temperatures aiming at investigating the adsorption mechanisms of the two dyes. The experimental results indicate that, for both MB and MO, the adsorption capacity increases with increasing temperature, with slight differences in the case of MO. Comparatively, the CuO nanoparticles show a higher MB adsorption capacity with respect to MO. A modelling analysis is carried out with a multilayer model derived from statistical physics, selected among a group of models, each hypothesizing a different number of adsorbed molecules layers. The analysis of model parameters allows determining that the adsorbate molecules exhibit a non-parallel orientation on the surface of biosynthesized CuO nanoparticles and each functional group of the adsorbent binds multiple molecules, simultaneously.The model also allows determining the number of dye molecule layers formed on adsorbent surface, in all the cases resulting higher than three, also confirming the effect of temperature on the maximum adsorption capacity.Specifically, the total number of dye layers formed on biosynthesized CuO nanoparticles surface exhibited a range of 4.17-4.55 for MB dye and of 3.01-3.51 for MO dye.Finally, the adsorption energies reveal that adsorption likely involves physical forces (all resulting all below 22 kJ/mol), i.e. hydrogen bonding and van der Waals forces. The adsorption energies for the interactions between dye molecules are lower than those calculated for the interactions between the dye molecules and the adsorbent surface.

Statistical physics modeling and interpretation of the adsorption of enantiomeric terpenes onto the human olfactory receptor OR1A1.

The statistical physics approach has been well studied by our research team for liquid and gaseous adsorption systems. This treatment is based on the grand canonical partition function to give new interpretations of the adsorption process at molecular level for chemical senses: olfaction and taste. This work represents a contribution to understand the olfaction mechanism of four of enantiomeric terpenes by applying a statistical physics treatment that allows giving a physico-chemical meaning to parameters involved in the analytical model. It is possible to estimate the number of adsorbed molecules per site, the anchorage number, the receptor density, the concentration at half saturation and the molar adsorption energy. Through this selection of the best fitting model and through fitted values of these parameters, we showed that the adsorption of carvone and limonene enantiomers is not a multilayer process but a monolayer monosite process (monolayer adsorption model with identical and independent sites (n ≠ 1)). The physico-chemical model parameters can be used for the energetic characterization of the interactions between the carvone and the limonene enantiomers and the human olfactory receptor OR1A1 and the determination of an olfactory band of order of 14 kJ/mol, 7 kJ/mol, 9 kJ/mol, 8 kJ/mol for (R)-(-)-carvone, (S)-(+)-carvone, (R)-(+)-limonene and (S)-(-)-limonene, respectively, through the determination of the adsorption energy values and the adsorption energy distributions (AEDs). Thanks to the grand canonical formalism in statistical physics, the negative values of the Gibbs free enthalpy indicate that the adsorption process of the four enantiomeric terpenes onto the human olfactory receptor OR1A1 was spontaneous. The exothermic adsorption mechanism involved in the olfactory perception was explained via the negative values of the internal energy.

Investigation of mouse eugenol olfactory receptor activated by eugenol, vanillin and ethyl vanillin: Steric and energetic characterizations.

Steric and energetic characterizations were performed for the adsorption of eugenol (EG), vanillin and ethyl vanillin (EV) onto the mouse eugenol olfactory receptor mOR-EG by using a proposed model expression established by statistical physics methods. We started with a modeling of dose-response curves. The calculated curves fit well the experimental data and the physico-chemical model parameters can be used for the characterization of the interactions between the eugenol, vanillin and ethyl vanillin molecules and the mouse eugenol receptor and the determination of the olfactory band for these three odorant molecules through the determination of the adsorption energy values and the adsorption energy distributions. Furthermore, thermodynamic functions of the odorant adsorption such as the configurational entropy, Gibbs free enthalpy and internal energy were calculated and their negative values indicate that the adsorption process included in the olfaction mechanism was exothermic and spontaneous nature.

Stereochemical study of mouse muscone receptor MOR215-1 and vibrational theory based on statistical physics formalism.

In the biosensor system, olfactory receptor sites could be activated by odorant molecules and then the biological interactions are converted into electrical signals by a signal transduction cascade that leads the toopening of ion channels, generating a current that leads into the cilia and depolarizes the membrane. The aim of this paper is to present a new investigation that allows determining the olfactory band using a monolayer adsorption with identical sites modeling which may also describe the static and the dynamic sensitivities through the expression of the olfactory response. Moreover, knowing the size of receptor site in olfactory sensory neurons provides valuable information about the relationship between molecular structure and biological activity. The determination of microreceptors and mesoreceptors is mostly carried out via physical adsorption and the radius is calculated using the Kelvin equation. The mean values of radius obtained from the maximum of the receptor size distributions peaks are 4 nm for ℓ-muscone and 6 nm for d-muscone.