Theoretical study of the olfactory perception of floral odorant on OR10J5 and Olfr16 using the grand canonical ensemble in statistical physics approach

Abstract

In this work, two experimental dose-response curves of lyral molecules on the OR10J5 and the Olfr16 were employed in order to examine the evolution of physico-chemical parameters involved in the selected statistical physics model(s) to investigate the human and the mouse smelling of a floral scent. Indeed, one layer adsorption model on one type of sites with one energy (1LAM1T1E) and one layer adsorption model on two types of sites with two energies (1LAM2T2E), considered as appropriate models for the adsorption of lyral molecules on the OR10J5 and Olfr16, respectively, have been applied to fit the experimental data. Stereographic and energetic physico-chemical parameters, namely: the maximum response(s) at saturation, the number of docked molecules per olfactory receptor binding site and the concentration(s) at half saturation, were investigated to retrieve helpful information to describe the adsorption process putatively introduced in the olfaction perception. Thus, the advanced modeling results indicated that the studied molecules were docked with a non-parallel orientation (n > 1). Furthermore, for the two olfactory systems, the molar adsorption energies estimated from curves modeling were inferior to 11 kJ/mol, which showed the physisorption process of the adsorption of lyral molecules on OR10J5 and Olfr16. The 1LAM2T2E and the 1LAM1T1E were applied to estimate the OR10J5 and the Olfr175 RSDs, respectively. Hence, lyral RSDs were spread out from 0.7 to 20 nm with maximums at about 4 nm for OR10J5 and at about 3.65 nm for Olfr16. In addition, by using the two advanced models, the olfactory responses of lyral on OR10J5 and Olfr16 can be used for the energetic characterization of the lyral-OR10J5/Olfr16 binding sites interactions and allowed access to the adsorption energy distributions (AEDs). Then, two approximate olfactory bands can be determined for lyral molecules docked on OR10J5 and Olfr16, which are defined between 3 and 15.5 kJ/mol and between 3.5 and 13.5 kJ/mol, respectively. Lastly, thanks to the proposed models the adsorption entropy of the studied systems can be calculated to describe the disorder and the order on OR10J5 and Olfr16 surfaces (disorder peak of the two olfactory systems was attained when the equilibrium concentration was equal to the concentration at half saturation). Furthermore, the Gibbs free enthalpy and the internal energy were estimated and their negative values indicated that the adsorption phenomenon involved in the olfactory perception was spontaneous and exothermic nature.

Keywords: Adsorption energy distribution; Adsorption entropy; One layer adsorption model on one type of sites with one energy; One layer adsorption model on two types of sites with two energies; Receptor site size distribution; Statistical physics; Thermodynamic functions.