Electron transfer dissociation. ETD

Electron transfer dissociation (ETD) is an ECD-like method with most of the same characteristics [21]. Like ECD, ETD yields abundant peptide backbone c- and z-type ions while often retaining such labile groups as peptide O/TV-glycosylation and phosphorylation [22]. Unlike ECD, ETD can be performed in the presence of an RF field. Here, anions created in a chemical ionization (Cl) source (see Section 2.1.7) are used as electron donors but the fragmentation pathways are essentially the same as for ECD. Commercial linear QIT instruments have recently become available with the ETD option. 

Electron-capture dissociation (ECD) [1] and electron-transfer dissociation (ETD)... 

To bring the power of ECD to ion trap analysers, a new ECD-like activation method has been developed [58]. This method, which is called electron transfer dissociation (ETD), uses gas-phase ion/ion chemistry to transfer an electron from singly charged aromatic anions to multiply charged ions. The mechanism of this method and the observed fragmentation pathways are analogous to those observed in ECD. 

S.-I. Wu, A. F. R. Huhmer, Z. Hao, and B. L. Karger, On-line LCMS approach combining collision-induced dissociation (CID), electron transfer dissociation (ETD), and CID of an isolated charge-reduced species for the trace-level characterization of proteins with post-translational modifications, J. Proteome Res., 6 (2007) 4230 -244. 

To address some of the issues associated with CID of phos-phopeptides, new strategies for ion activation/dissociation have been introduced recently in the context of phosphoproteomics. In particular, electron transfer dissociation (ETD) is emerging as a promising new strategy for MS/MS-based phosphopeptide analysis (22, 23). 

Electron-transfer dissociation (ETD) is a variation of ECD, in which an ion-ion reaction, for example, between an anthracene anion and a multiprotonated peptide cation, is used to transfer an electron to the peptide ion.64,78 Similar to ECD, subsequent fragmentation of the odd-electron ions produces c- and z -type sequence-specific ions. ETD is also better suited for investigating phosphorylation and glycosylation. 

A functionally similar dissociation method, electron transfer dissociation (ETD) was more recently reported (32), specifically for use on QIT instruments, although it is also beginning to be adapted to other mass analyzers. ETD is accomplished by electron transfer to the analyte from a negatively charged species that is produced in a chemical ionization source and directed into the region where the analyte ions are trapped. For peptides and proteins, it produces spectra that... 

FIGURE 3.1 Quadrupole ion trap mass spectrometers are capable of concatenating multiple, unique ion-processing methods during routine, robust, day-to-day operation for example, a user can combine electron transfer dissociation (ETD), proton transfer reaction (PTR), collision-induced dissociation (CID), and ion attachment (lA) in any order in but a single scan. This ability highlights how trapped-ion instruments are capable both of mass analysis and of functioning as an ion reaction vessel. 

ELECTRON TRANSFER DISSOCIATION (ETD) COUPLED WITH COLLISION-INDUCED DISSOCIATION (CID)... 

Electron Transfer Dissociation (ETD) and Electron Capture Dissociation (ECD)... 

There are other means to fragment ions and thus produce MS/MS spectra that contain information different from that obtained by conventional CID. Electron transfer dissociation (ETD) and electron capture dissociation (ECD) are gaining popularity because they provide structural information that is difficult to obtain, e.g., the preservation of phosphates in the LC-MS/MS analysis of peptides obtained from the enzymatic digestion of phosphoproteins. 

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