Tuesday, August 23, 2016
Double laser dissociation in the HCD cell of a Q Exactive!
All summer, at virtually the same time every single morning the same two questions have occurred to me:
1) How many other people are reading JASMS in their bathroom right now? Guess it depends on the fiber intake of the average mass spectrometrist -- and where they have JASMS delivered. This is probably a question that could be answered with some effort, but I doubt I'll ever make it a priority to find out. A SurveyMonkey and some epidemiology stats could shed some light, but a tracking App of some kind would probably be necessary to get real numbers. Is it worth the time? Or is it better for it to be one of those deeper philosophical mysteries that we shouldn't ever try to investigate because it would reveal more about us than we should ever really know?
2) Why doesn't anyone I know have a mass spec equipped with lasers? This is the important one.
Cause...guess what?!?!....the cover of JASMS is another group with a....
...in their HCD cell. I know...I promised not to write about any more of these, but this one raised the bar. They put 2 kinds of lasers in their HCD cell and used it to analyze intact ubiquitin.
One laser is high energy and another is low energy, but it appears they can use them both simultaneously.
They read out the fragments in the Orbitrap at 140k resolution with 3 microscans and they sum 50 scans for their fragment analysis. This is, arguably, an awful long time to accumulate fragments of an 8.5kDa protein. But this is a fragmentation method development paper, so we don't really mind about that.
How's it do? 84% sequence coverage of the +13 charge state! Not so bad!
Now...when is someone in Maryland getting a laser HCD cell?!?!