A quantitative analysis of the inelastic electron tunnelling spectrum of the formate ion

Neuroreceptor activation by vibration-assisted tunneling

G protein-coupled receptors (GPCRs) constitute a large family of receptor proteins that sense molecular signals on the exterior of a cell and activate signal transduction pathways within the cell. Modeling how an agonist activates such a receptor is fundamental for an understanding of a wide variety of physiological processes and it is of tremendous value for pharmacology and drug design. Inelastic electron tunneling spectroscopy (IETS) has been proposed as a model for the mechanism by which olfactory GPCRs are activated by a bound agonist. We apply this hyothesis to GPCRs within the mammalian nervous system using quantum chemical modeling. We found that non-endogenous agonists of the serotonin receptor share a particular IET spectral aspect both amongst each other and with the serotonin molecule: a peak whose intensity scales with the known agonist potencies. We propose an experiential validation of this model by utilizing lysergic acid dimethylamide (DAM-57), an ergot derivative, and its deuterated isotopologues; we also provide theoretical predictions for comparison to experiment. If validated our theory may provide new avenues for guided drug design and elevate methods of in silico potency/activity prediction.

A method for the calculation of odor character from molecular structure

The relationship between molecular structure and odor character is one of the most complex structure-activity problems in biology. Despite over a century of effort, it remains unsolved, and synthesis of new odorants still proceeds largely by trial and error. In previous work, I have argued that the reason for this failure lies in a mistaken assumption, namely that molecular shape determines odor character. Instead, I have taken up and extended an old idea (Dyson, 1938) according to which vertebrate olfactory receptors detect odorants by their molecular vibrations. I propose that the detection mechanism is inelastic electron tunnelling. If this is correct, there should be a correlation between the tunnelling vibrational spectra of odorants and their odor character. Here, using semi-empirical quantum chemistry methods and a simple calculation method for tunnelling mode intensities, I calculate the spectra of structurally diverse odorants belonging to various odor categories. With few exceptions, the calculated spectra of bitter almonds, musks, ambers, woods, sandalwoods and violets strongly correlate with odor character.