TIMSTOF resolving both positional and structural histone markers!

 

This is just a solid all-around story on how having just a little extra dimension in your data can help you see some past ions that have the same exact mass and charge (and darned close retention times!) 

The figure above at the top is my favorite part. The ions in panels A, B and C all come off the column at right about 26.80 minutes. And they're all +3 ions at 548.658. 

Check out how different the 1/K0 values are for A and B! Something weird is up there, right? A is at/around 0.82 and B is about 0.9. That's well outside the 0.05 window that people seem to beo okay with putting on these data. Looks like different molecules, right? 

And they are. Well - sorta - they're the same linear peptide sequence but the PTMs are on different sites of these derivatized (propionylated) histone peptides.

C isn't quite as clear cut. The 1/k0 is about the same, so you're back to looking at MS/MS fragments and working them out (which, admittedly, you can see in A vs B, however - without the IMS separating them out, there's a pretty solid chance here that you're just going to see one really complicated spectrum with all 3 in them, right? 

I'm pretty sure they ran the same samples on an Exploris 480 and a TIMSTOF and they can work out most with the former, but they get some new ones in the TT data that they didn't see at all. For people who know what to do with these histone codes, getting more peptides in each sample is something that always seems to make them happy.