Electron-capture dissociation

Electron-capture dissociation (ECD) is a method of fragmenting gas-phase ions for structure elucidation of peptides and proteins in tandem mass spectrometry.

[3] Electron-capture dissociation typically involves a multiply protonated molecule M interacting with a free electron to form an odd-electron ion.

[19][20] The mechanism of ECD is still under debate but appears not to necessarily break the weakest bond and is therefore thought to be a fast process (nonergodic) where energy is not free to relax intramolecularly.

[21] In a similar MS/MS fragmentation technique called electron-transfer dissociation, the electrons are transferred by collision between the analyte cations and reagent anions.

It successfully cleaved 87 of 208 backbone bonds and provided the first direct characterization of a phosphoprotein, bovine β casein, simultaneously restricting the location of five phosphorylation sites.

It has advantages over CAD to measure the degree of phosphorylation with a minimum number of losses of phosphates and for phosphopeptide/phosphoprotein mapping, which makes ECD a superior technique.

[32] ECD has been coupled with capillary electrophoresis (CE) to gain insight into structural analysis of mixture of peptides and protein digest.

[36][8] Recently, Atmospheric pressure electron capture dissociation (AP-ECD) is emerging as a better technique because it can be implemented as a stand-alone ion-source device and doesn't require any modification of the main instrument.

[40][41] Native electron capture dissociation (NECD) was used to study cytochrome c dimer[42] and has been recently used to elucidate iron-binding channels in horse spleen ferritin.

ECD's single bond cleavage tendency makes the interpretation of product ion scans simple and easy for polymer chemistry.