Molecule shape affects smell perception, says study
In a paper published in the Chemistry & Biology journal a team of researchers led by Dr. Kevin Ryan from The City College of New York set out to investigate how our sensory perception of scent-producing molecules is affected by molecule size.
They claim that their findings shed light on how our sense of smell works and have potential applications in the design of flavors and fragrances.
When scent-producing molecules, known as odorants, pass through the nose, they trigger intracellular changes in a subset of the approximately 400 different varieties olfactory sensory neurons (OSN) housed in the nose’s internal membrane tissue.
The unique reaction pattern produced, known as the olfactory code, is sent as a signal to the brain, which leads to perception of odors.
Goal and methodology
Ryan and his team wanted to learn how the receptor cells respond when odorants change their shape. They studied the odorant octanal, an eight-carbon aldehyde that appears in many flowers and citrus fruits and is structurally flexible so can adapt to a variety of different shapes.
The researchers designed and synthesized eight-carbon aldehydes that resembled octanal, but had their carbon chains locked by adding one additional bond. These molecules were tested on genetically engineered OSNs known to respond to octanal.
Results of the study
The aldehyde molecules that could stretch to their greatest length triggered strong activity in the OSNs. However, those molecules whose carbon chains were constrained into a U shape blocked the receptor and left the cell unable to sense octanal.
“Conformationally constrained odorants were more selective in the number of OSNs they activated,” said Ryan.
“The results indicate that these odorant molecules might be able to alter fragrance mixture odors in two ways: by muting the activity of flexible odorants present in a mixture and by activating a smaller subset of OSNs than chemically related flexible odorants. This would produce a different olfactory code signature.”
