Site Title

This study is a couple of years old, but it highlights a whole clever way of detecting pathogens  — amplifying DNA and then doing mass spectrometry of the amplicons.

Advantages:
-You can start with virtually no DNA and make a ton of it
-MALDI-TOF is fast when you’ve got a ton of samples to screen
-MALDI instruments, while maybe not very common in research environments, are increasingly common in clinical labs. (Big question, though, is the flexibility — I think that a lot of these are locked down to performing one specific assay, but — still — those places would have staff with the technical expertise to prep the samples and run the instruments
-If you pick primers well, you’d be resistint to mutations in the viral strains

Cons:
-PCR takes time. Is it faster than it was?
-It takes some people a long time to make primers and to verify they don’t cross-react. (I’ve heard tools have gotten better)
-MALDI is almost always connected to low power TOF devices (sensitivity, resolution and accuracy are the things that are typically the low part)

Check out this alternative technique that would alleviate some of this —

Same general idea — 15 years ago — this group amplified their virus DNA (SARS-coronavirus) and then did FTICR….are there a few thousand smaller, faster FTMS devices around the world right now? If you’ve already done PCR would you even need to couple it to HPLC? FIA-MS on an Orbitrap?

Sorry if you’re tired of hearing about these viruses, but I’m motivated to read/write about it

On the topic of the 2019-nCOV (Wuhan) coronavirus — check out this beautiful resource from NextStrain!

If you are working on this from a proteomics/mass spec/clinical detection perspective and want to talk, please reach out (orsburn@vt.edu). I’d be happy to lend a hand developing/troubleshooting assays or by (much more usefully) connecting you to people who could be of great assistance.

And — while I’m sleepy rambling — check this out — ModPred (www.modpred.org) thinks palmitoylation is a dominant PTM — if you are developing peptide specific assays — I’d skip that entire protein terminus.

I’m a little behind on this and don’t have actual data to compare yet, but MaxQuant.Live 1.2 is up for download.

Important factor for many of us — it still appears to rely on the same Foundation and Tune 2.9 (no 2020 mandatory upgrades if you were already using it in 2019).

The interface looks a little cleaner, but if  you were also hoping for some magical new data acquisition method to appear in the App store, you’d also be disappointed.

Given how active the developers have been on the awesome MaxQuant.Live Google group discussion forum, I think we’re looking at a great software that still hasn’t been utilized to it’s potential, but has had some minor bugs ironed out.

A great way to see trends in proteomics is to go to ProteomeXchange and see what everyone is uploading.

The word “spatial” is completely blowing up. I think there are a couple versions of the modern “spatial” techniques. APEX, however, might be the best example. There is a great overview of this technique on the Krogan lab website that you can view here (I don’t want to steal their nice image!)

Want the 6 18 second description/reminder?
1) You make a version of your protein of interest with a peroxidase on it and then you put it into your biological system and let it interact with all it’s friends.
2) You put some biotin-phenols that float around in your system doing (presumably) no harm or alterations to your system
3) !!SURPRISE!! your system by adding hydrogen peroxide!
4) Nothing special happens to any other proteins (except normal H2O2 effects, I guess) but your protein of interest has that peroxidase on it –it reacts with the biotin phenols around it which causes all it’s local protein friends to be labeled with biotin!
5) Pull down the biotin labeled proteins and now you know all the proteins in the general area of your protein of interest. Cool, right?

(It is a bit more complex than this. You don’t want the APEX fusion being expressed all the time, for example, you can wait and activate it when your cells get ot the right stage — you also need ot quench the reaction, but now I need to change how many seconds this took again…)

However, if you want to see it in action in a medical context — check out this new preprint!

 
This group used multiple APEX Fusions to study stress granules (SG)s which according to the authors “form in response to a variety of cellular stresses by phase-separation of proteins associated with non-translating mRNAs” (yes, stolen from the first sentence of the abstract).

Unlike a lot of spatial labeling techniques — this one requires nothing special from the mass spectrometer. The biotin labeled proteins are pulled down and digested. This group used a QE Plus for part of the study and it looks like they upgraded to a QE HF at some point. The LC separation was a long (3hour) gradient on 50cm columns. A relatively cycle time is maintained between the two instruments by using 17,500 resolution for MS/MS on the Plus and 30,000 resolution on the HF. The data processing here is MaxQuant and it looks very typical.

With this system set up, the experiment gets more complex, with the addition of ALS linked dipeptides that show alterations in the stress granules and the SUMoylation — which is where the biology goes beyond me.

What I do get:
1) A fantastic application of this powerful new technique
2) A method that demonstrates that I could definitely do my part of this.
3) Important new understandings into the progression of a protein disease?