How ECD can help you?
Electron dissociation techniques such as electron-capture dissociation (ECD) and electron-transfer dissociation (ETD) are considered low energy fragmentation techniques and therefore offer the ability to dissociate molecules in a manner that allows for the retention of more labile bonds. It is particularly useful when investigating larger peptides and proteins as the fragmentation induced gives better coverage than higher energy techniques such as collision-induced dissociation (CID) and has also been shown to retain post-translational modifications (PTMs) allowing for a significantly improved understanding of the protein structure. Until recently ECD was restricted first to FTMS instruments and then some newer non-FT based mass spectrometers. Numerous papers have been produced showing the usefulness of these low energy dissociation techniques and a good selection of publications can be found at ScienceDirect for ECD in general and on e-MSion’s website for the e-MSion ExD cell in particular.
Enhanced structural information
For proteins and peptides, ECD has the ability to indiscriminately cleave the backbone N-Cα bond, while leaving the more labile side-chain modifications intact. Combining ECD and CID spectra can potentially provide more complete data for de-novo sequencing. Because post-translational modifications such as phosphorylation, carboxylation, glycosylation, and sulfation are less easily lost in ECD than in CID, ECD assignments of their sequence positions are far more specific. This is particularly useful when studying for example protein interactions or conducting structural biology experiments. Combining this with ion mobility adds even more useful information and ECD is definitely a key weapon in the mass spectrometrist’s arsenal.
When aiming for structural information by H/D-exchange, fragmentation by ECD – in contrast to CID – does give significantly less rise to hydrogen scrambling. This makes the analysis of the obtained data much simpler. Furthermore, ECD is able to efficiently fragment larger peptides than CID, thereby giving access to areas with only a few enzymatic cleavage sites, such as e.g. transmembrane domains, for H/D exchange analysis.
Don’t I need expensive instruments for it though?
In 2015 e-MSion Inc. was founded to make ECD available to the wider MS community as a retrofittable device on non-FT-ICR spectrometers. At MS Vision we have many years of experience of making modifications to existing hardware to improve its capabilities beyond those of its original intended use. We are happy to be able to be working in collaboration with e-MSion to bring this technology to owners of existing Waters Synapt G2 and ThermoFisher QExactive instruments as retrofittable upgrades. The first systems in Europe have already been equipped with the cells and we will be happy to provide you with new analytical capabilities on your existing instrument. MS Vision is also capable to fully support and service the modified systems up to Platinum service level.
What does it give me that I can’t already get?
The ExD Cell produces ECD fragmentation similar to FT-ICR-ECD, but on workhorse mass spectrometers like Q-TOFs and QExactives. The ability to perform simple electron-based fragmentation enables valuable new types of data and time-saving workflows. ECD tends to produce mainly c- and z-type ions and as a result the spectra produced tend to be less congested thus making interpretation and top-down sequencing simpler. The localized activation preserves the PTMs and thereby enables the identification of the site of PTMs such as phosphorylation and glycosylation etc. especially when combined with native MS. This can be achieved in conjunction with UHPLC, HPLC, CE and IMS thus making the technique compatible with your standard workflows.