# Electron-transfer dissociation

(Redirected from Electron transfer dissociation)

Electron-transfer dissociation (ETD) is a method of fragmenting ions in a mass spectrometer.[1][2] Similar to electron-capture dissociation, ETD induces fragmentation of cations (e.g. peptides or proteins) by transferring electrons to them. It was invented by Donald F. Hunt, Joshua Coon, John E. P. Syka and Jarrod Marto at the University of Virginia.[3]

## ETD fragmentation

ETD does not use free electrons but employs radical anions (e.g. anthracene or azobenzene) for this purpose:

$[M + nH]^{n+} + A^- \to \bigg[ [M + nH]^{(n-1)+} \bigg]^* + A \to fragments$.[4]

where A is the anion. ETD cleaves randomly along the peptide backbone (so called c and z ions) while side chains and modifications such as phosphorylation are left intact. The technique only works well for higher charge state ions (z>2), however relative to collision-induced dissociation (CID), ETD is advantageous for the fragmentation of longer peptides or even entire proteins. This makes the technique important for top-down proteomics.

Much like ECD, ETD is believed to be particularly effective for peptides with modifications such as phosphorylation.[5]