Saturday, May 23, 2020

Rereading -- FAST and Low-cost detection of SARS-CoV-2 peptides by LCMS!

After a few hours of sleep, let's looks at this awesome new preprint again!

What's it do? tries to establish our beloved LCMS systems and shotgun proteomics work into a real life diagnostic assay for the virus.

How'd they do it? They got some infected nasopharyngeal swabs and removed 200uL of the material for digestion.

They used SP3 digestion overnight (following reduction/alkylation) they prepped with a Hamilton Starlet --  I think it was this one, but this might be a newer model?

They used microflow at first on a QE HF-X. And that was fast -- that was like 9 minutes.

Then when everything looked great -- they went Turbulent Flow(??) with a Triple Quad (TSQ Altis) and cranked up the speed dramatically.

Do you know about these multiplex HPLC things? Here is an example image.

You see them in biopharma labs all the time. You run multiple gradients simultaneously and you either do the UV Absorbance or mass spectrometry on the point in each gradient that you're interested in.

For example, if your peptide of interest comes off at 33 minutes and that's all you care about, why waste that precious mass spectrometer looking at the whole gradient? Just switch over at 32 minutes, ionize till 34 and switch to the next column and gradient. HPLC pumps are $30k? Switching valves are $2k? 4 pumps and 2 switching valves and you're doing the work of 4 LCMS systems for less than the price of two.

Now...your plumbing flowchart kinda looks like this in the end ---

-- but as long as nothing goes wrong, you're getting high throughput on the cheap!

I'm not familiar with the difference between high speed multiplexing and Turbulent Flow, but I think this all still makes sense.

This is how they get to crazy throughput. In theory -- 500 individual samples screened per instrument per day. Which is fantastic!

Again. Great paper. I should sleep more. And read slower. Awesome work and a huge congratulations to this team.

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