The ETD source exploits the open architecture of the LTQ™ and is physically coupled to the back-end of the two-dimensional ion trap. The traditional electrospray source remains on the front-end, and collision-induced-dissociation will be available as well. This flexible design allows the addition of other ion reaction types (such as PTR) in the future. The ETD upgrade is currently available as an upgrade on new and existing LTQs.
The ETD upgrade will greatly enhance the mapping of phosphorylation sites and other modifications. Because large peptides can be successfully fragmented by ETD, this upgrade will enable top-down-sequencing of small proteins/large peptides and will support bottom-up proteomics using enzymes that make larger peptide fragments.
Learn more about ETD options and technique in the following papers and presentations: