Adsorption of 2-phenylethanethiol on two broadly tuned human olfactory receptors OR1A1 and OR2W1: Interpretation of the effect of copper ions via statistical physics monolayer adsorption model

Abstract This paper aims to investigate the effect of metal especially copper ions on the adsorption of a key food odorant (2-phenylethanethiol) on two human olfactory receptors OR1A1 and OR2W1 that was interpreted via a statistical physics monolayer model. To this purpose, four experimental dose-olfactory response curves were used without and with the presence of Cu2+ for each human receptor. In order to reach a theoretical interpretation of the experimental data and understand the effect of the used metal on adsorption process introduced on the olfaction mechanism, a statistical physics monolayer adsorption model with identical and independent sites was applied. The used model showed that the presence of copper ions decreased the efficacy (olfactory response at saturation) of 2-phenylethanethiol key food odorant activating OR1A1, suggesting a negative allosteric action. However, the presence of Cu2+ reduced the potency (concentration at half saturation) of the studied thiol key food odorant in activating OR2W1, suggesting an orthosteric competitive action. Furthermore, the molar adsorption energies retrieved from data analysis varied from 5.568 to 9.886 kJ/mol in studied systems, whose values showed that the process based on a physical adsorption. Lastly, the dose-olfactory response curves of 2-phenylethanethiol on two broadly tuned human olfactory receptors OR1A1 and OR2W1 provided access to the olfactory receptor site size distribution (RSD) and also the adsorption energy distribution (AED).