Advanced investigation of a putative adsorption process of nine non key food odorants (non-KFOs) on the broadly tuned human olfactory receptor OR2W1: Statistical physics modeling and molecular docking study

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In the present paper, statistical physics formalism was used to understand the olfactory perception via the investigation of dose-olfactory response curves of a putative adsorption process of nine non key food odorants (non-KFOs) on the broadly tuned human olfactory receptor OR2W1, in order to quantitative characterize the interactions between the nine studied non-KFOs, i. e., furfuryl sulfide, furfuryl disulfide, benzyl methyl disulfide, furfuryl methyl disulfide, benzyl methyl sulfide, 1-phenylethanethiol, benzyl mercaptan, furfuryl methyl sulfide and 3-phenylpropanol molecules and OR2W1 binding sites at a molecular level. Two advanced adsorption models have been proposed: the advanced monolayer monoenergy model (monolayer model with identical and independent olfactory receptor binding sites) (Model 1) and the advanced monolayer model with two independent types of olfactory receptor binding sites (Model 2). It was concluded that the monolayer monoenergy model was selected as the most adequate model to fit the experimental dose-olfactory response curves tabulated in literature. Actually, the numerical values of the three fitted physico-chemical parameters (RM1, n and C1) were obtained by a non-linear regression. Indeed, modeling results suggested that the number of docked non-KFOs per OR2W1 binding site n values (1.24 < n < 1.94) was always superior to 1, which indicated the non-parallel orientation of the studied odorants on the olfactory receptor and the multi-molecular adsorption mechanism. The estimated molar adsorption energy ΔEa values (ranged from 6.07 to 12.16 kJ/mol) for the nine olfactory systems confirmed the physical the exothermic characters of the adsorption process since ΔEa values were lower than 40 kJ/mol and positive. Furthermore, these estimated parameters were applied to characterize stereographically and energetically the interaction between the nine non-KFOs and OR2W1 through the determination of the human receptor binding site size distributions (RSDs) and the adsorption energy distributions (AEDs), which were spread out from 0.25 to 6.50 nm and from 0 to 22.50 kJ/mol, respectively. The docking computation between these nine non-KFOs and OR2W1 proved that the estimated binding affinities were belonged to the adsorption energies spectrum in general and the specific adsorption energy band or the molecular vibration modes limited spectrum (between 2.50 kJ/mol and 17 kJ/mol) (approximate olfactory band).