Electron transfer dissociation

Electron transfer dissociation (ETD) is a method to fragment 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.

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ETD fragmentation

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

$[M + nH]^{n+} + A^- \to \bigg[ [M + nH]^{(n-1)+} \bigg]^* + A \to fragments$ .^[3]

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.

References

^ Syka JE, Coon JJ, Schroeder MJ, Shabanowitz J, Hunt DF (2004). "Peptide and protein sequence analysis by electron transfer dissociation mass spectrometry". Proc. Natl. Acad. Sci. U.S.A. 101 (26): 9528-33. doi:10.1073/pnas.0402700101. PMID 15210983.
^ Mikesh LM, Ueberheide B, Chi A, Coon JJ, Syka JE, Shabanowitz J, Hunt DF (2006). "The utility of ETD mass spectrometry in proteomic analysis". Biochim. Biophys. Acta 1764 (12): 1811-22. doi:10.1016/j.bbapap.2006.10.003. PMID 17118725.
^ McLuckey SA, Stephenson JL (1998). "Ion/ion chemistry of high-mass multiply charged ions". Mass spectrometry reviews 17 (6): 369-407. doi:<369::AID-MAS1>3.0.CO;2-J 10.1002/(SICI)1098-2787(1998)17:6<369::AID-MAS1>3.0.CO;2-J. PMID 10360331.