Researchers have finally seen how some smell receptors bind to odor molecules
quantamagazine.org
quantamagazine.org
This finding recently made a big splash at AChemS 2021 (the annual meeting for the Association for Chemoreception Sciences). And it actually is a really big deal. A protein structure is extremely information rich, telling you where all of the atoms of a given protein are (ish). Before this finding, there were NO structures of any olfactory receptor, and historically the publication of the first structure of a given biomolecule has been a watershed moment for that field (insulin, ribosome, many other examples).
What's more, they used the structural information to rationally engineer their olfactory receptor, expanding the binding pocket and changing how the receptor responds to different odorants. That was pretty much impossible to do before this. So, this is a pretty huge finding, and will definitely encourage more structural work on olfactory receptors in the future.
If I had to poke a hole in this finding, it would be that insect olfactory receptors are substantially different from mammalian olfactory receptors. But in my opinion, it seems that the buzz about this paper is definitely justified. Very cool!
Had no idea it's just a theory. I've lived many years "knowing" that we detect smells due to their shapes.
But while searching, I came across this: https://www.bbc.com/news/science-environment-21150046
I realize that this has long been considered crackpottery, and there has never been a reasonable sense of a mechanism for it. But it did seem to offer at least a stab at a couple of questions that didn't have good answers in the ordinary lock-and-key model of olfaction, such as why sulfur-containing molecules all smell "sulfury" if they all unlock different locks.
As far as I can tell the idea sorta just died out. A lot of work was done trying to make odor molecules with different isotopes, with intriguing but inconclusive results.
Still, I've been kinda curious to see if the theory was finally over and done.
I understand that some kinds exist (and some are even off the shelf) but they tend to be pretty limited in what they can 'sniff'.
[1]https://hms.harvard.edu/news/how-covid-19-causes-loss-smell
Probably the olfactory loss continues to some degree for a long time. There may be some nerve damage even if the cells that are targeted by the virus aren't nerves. These then will take a long time to heal. Smells and memories of them seem fixed, but at least in mice, appear to be a flexible entity, with successive exposure to a particular smell causing different patterns of brain activity at every new exposure (https://www.theatlantic.com/science/archive/2021/06/the-brai...) "representational drift" is the key word. This particular system is highly regenerative. It can be damaged easily, and it can recover easily. Not to say that anyone should have to get COVID19.
You probably get into this in the preprint. I'll have a read before I prognosticate further!
It would be interesting to look at the gene family in the HPRC.
https://www.itu.int/en/ITU-T/focusgroups/net2030/Documents/W...
The nut:
> [T]he limited repertoire of receptors on its olfactory sensory neurons must somehow recognize a vast number of compounds. So an individual receptor has to be able to respond to many diverse, seemingly unrelated odor molecules.
> That versatility is at odds with the traditional lock-and-key model governing how selective chemical interactions tend to work. [....]
> Now, new work has taken a crucial and much anticipated step forward in elucidating the beginning stages of the olfactory process. In a preprint posted online earlier this year, a team of researchers at Rockefeller University in New York provided the first molecular view of an olfactory receptor as it bound to an odor molecule.