What the hell is Ion mobility?

Edited/updated:  2/4/14.

Thanks for all the comments, guys!  I'm going to try and reflect these comments.

I've been hearing about ion mobility for years, but I haven't committed anything to long term memory.  But I'm going to.  Cause this shit seems pretty awesome.

FAIMS (pronounced fAmeZ) is a way of focusing ions as they enter your mass spectrometer.  One proponent described it to me as almost a 3rd dimension of separation. Essentially, it appears that you apply an electrical current to the ions at the entrance to the mass spectrometer allowing you to focus the ions into a particular packet (i.e., z=2 at voltage x, and z=2 at voltage x + 1)

This can open a whole realm of possibilities.  How awesome would your ion statistics be if you could tell your search engine that this group of ions were doubly charged, while this second group were all triply charged?  It opens up a whole realm of possibilities.

How powerful is this technology?  Just to put it in perspective, if it is employed properly it can make a Xevo Synapt actually do something other than MS1!  No kidding!

In this new paper in Nature Methods from Ute Distler et al., these researchers describe the use of a similar technology to FAIMS, called TWIMS (traveling wave ion MS) in conjunction with MSe and use it to crank up the number of peptides and proteins hits on a HeLa database.  The energy used in the MSe fragmentation are directly affected by the FAIMS settings in order to optimize the energy range according to the charge states of the ions making it into the instrument.

The results are out of this world!  On a 300ng HeLa digest using nanoUPLC on 180 minute gradients, the group reports that they can reproducibly obtain around 3,800 unique proteins when using the IPI database.  This is almost up to the level of what I'd expect on an Orbitrap Velos running in standard high low in a data dependent experiment when searching against this same database.  For the Synapt this represents a huge increase in peptide/protein coverage (2 to 3 fold!) over a standard MSe run.

This makes me really excited because can you even imagine what FAIMS might do it it were coupled to the front of a mass spectrometer that could get already get that kind of coverage, or better?  If a Q Exactive under these conditions was obtaining 4,500 IPI proteins per run, could FAIMS double that?  Great days are ahead!

For more on how IPI can inflate your results, click here!

For more on FAIMS, check out these sites:
FAIMS.com
OwlStoneNanoTech
Or these videos

The FAIMS + MSe paper is entitled:  Drift time-specific collision energies enable deep coverage data-independent acquisition proteomics

Again, thanks for the comments.  I plan to read more about ion mobility (found a great review or 7, I'm sure one or more is open access).  I'll follow up later!