Docking theory of olfaction

Three years after Moncrieff proposed the theory, John Amoore speculated further that the over ten thousand smells distinguishable by the human olfaction system resulted from the combination of seven basic primary odors correlating to odor receptors for each, much as the spectrum of perceived colors in visible light is generated by the activation of three primary color receptors.

His most convincing work was done on the camphoraceous odor, for which he posited a hemispherical socket in which spherical molecules, such as camphor, cyclooctane, and naphthalene could bind.

Receptors in the odotope model recognize only small structural features on each molecule, and the brain is responsible for processing the combined signal into an interpreted smell.

Much current work on the docking theory focuses on neural processing, rather than the specific interaction between odorant and receptor that generates the original signal.

A study by Leslie B. Vosshall and Andreas Keller, published in Nature Neuroscience in 2004, tested several key predictions of the competing vibration theory and found no experimental support for it.

[15] Another study also showed that molecular volume of odorants can determine the upper limits of neural responses of olfactory receptors in Drosophila.

[16] A 2015 Chemical & Engineering News article on the "shape" versus "vibration" debate notes that in the "acrimonious, nearly two-decade-long controversy...on the one side are a majority of sensory scientists who argue that our odorant receptors detect specific scent molecules on the basis of their shapes and chemical properties.

The authors conclude: "These and other concerns about electron transfer at olfactory receptors, together with our extensive experimental data, argue against the plausibility of the vibration theory."

In commenting on this work, Vosshall writes "In PNAS, Block et al.... shift the "shape vs. vibration" debate from olfactory psychophysics to the biophysics of the ORs themselves.