Comment by Pick-A-Hill2019 | Hacker News Reader

Comment by Pick-A-Hill2019 | Hacker News Reader

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Pick-A-Hill2019

I know I may regret saying this* but have they considered vaporising/heating/burning the air sample to produce a spectrograph and then running an image recognition for comparison to known smells. A bit like you can produce a spectrograph of an mp3 and get an almost instantaneous hit if the track is previously known. Subtract out the known smells and the remaining is an unknown. Find similar shaped molecules and return their likely traits (musky, floral, almonds etc.) with a visual keyword cloud.

It is two different things – you either recognize a scent OR you identify a scent. Why not speed things up by running it as a two step process? Recognize = Rapid results, Identify = Best Guess at what it might smell like. I’m not sure how a human determines that there is a smell of gasoline, freshly cut grass and a hint of something else/unknown in the air rather than thinking hmmm, I do not recognize a scent that has aspects of cut grass AND gasoline AND an unknown therefore the whole scent is ‘unknown’.

*anon-experts that go ‘gosh, why didn’t those idjuts with multiple PhDs think of that’

What you're describing is GC-MS, which indeed returns a spectrographic signature that is used to identify a molecule. As noted by @Terr_, that tells you what a molecule is made of but not what shape it is. That being said, the smaller the molecule the easier it is to accurately predict what shape it will be. When computational methods become questionable, you move on to NMR (and a whole host of other techniques).

The real issue here is that olfaction involves a small molecule interacting with multiple different proteins for your body to "read" it. We're not so great at the whole predicting drug-protein interaction thing just yet - some closely related fields include virtual screening, molecular dynamics, protein crystallography, X-ray diffraction, and cryoEM (among others).

I think a spectrograph tells you more about the constituent elements in the sample, instead of the various shapes of various molecules that existed before you heated it.

Interesting point. Are there sensors/tools other than a spectrograph that could help? Some clever use of a camera or something?

I won't claim it's impossible, but... olfaction boils down to a small molecule protein interaction, similar to drug discovery. The scales in question are far too small for typical imaging devices; these objects are far smaller than the wavelength of visible light. CryoEM and X-ray diffraction are used in these domains, but don't apply in the manner you appear to have in mind. I suppose CryoEM technically counts as "clever use of a camera" though.

Your comment lead me down an interesting rabbit hole. Stumbled across this which might count - "Photoacoustic spectroscopy has become a powerful technique to study concentrations of gases at the part per billion or even part per trillion levels." https://chem.libretexts.org/Bookshelves/Physical_and_Theoret...

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