Electron transfer dissociation
Encyclopedia
Electron-transfer dissociation (ETD) is a method of fragmenting ions in a mass spectrometer. Similar to electron-capture dissociation, ETD induces fragmentation of cations (e.g. peptide
Peptide
Peptides are short polymers of amino acid monomers linked by peptide bonds. They are distinguished from proteins on the basis of size, typically containing less than 50 monomer units. The shortest peptides are dipeptides, consisting of two amino acids joined by a single peptide bond...

s or protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

s) by transferring electron
Electron
The electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...

s to them. It was invented by Donald F. Hunt
Donald F. Hunt
Donald F. Hunt is currently the University Professor of Chemistry and Pathology at the University of Virginia.- Early life and education :He received his B.S. and Ph.D...

, Joshua Coon
Joshua Coon
Joshua Coon is an associate professor of chemistry at the University of Wisconsin–Madison. His research focuses on mass spectrometry, specifically in its application to proteomics. Joshua Coon, along with John Syka, developed electron-transfer dissociation while working in Donald Hunt's lab at the...

, John E. P. Syka and Jarrod Marto at the University of Virginia
University of Virginia
The University of Virginia is a public research university located in Charlottesville, Virginia, United States, founded by Thomas Jefferson...

.

ETD fragmentation

ETD does not use free electrons but employs radical anions (e.g. anthracene
Anthracene
Anthracene is a solid polycyclic aromatic hydrocarbon consisting of three fused benzene rings. It is a component of coal-tar. Anthracene is used in the production of the red dye alizarin and other dyes...

 or azobenzene
Azobenzene
Azobenzene is a chemical compound composed of two phenyl rings linked by a N=N double bond. It is the best known example of an azo compound. The term 'azobenzene' or simply 'azo' is often used to refer to a wide class of molecules that share the core azobenzene structure, with different chemical...

) for this purpose:
.

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
Collision-induced dissociation
In Mass spectrometry, Collision-induced dissociation , referred to by some as collisionally activated dissociation , is a mechanism by which to fragment molecular ions in the gas phase. The molecular ions are usually accelerated by some electrical potential to high kinetic energy and then allowed...

 (CID), ETD is advantageous for the fragmentation of longer peptides or even entire proteins. This makes the technique important for top-down proteomics
Top-down proteomics
Top-down proteomics is a method of protein identification that uses an ion trapping mass spectrometer to store an isolated protein ion for mass measurement and tandem mass spectrometry analysis. The name is derived from the similar approach to DNA seqencing...

.

Much like ECD, ETD is believed to be particularly effective for peptides with modifications
Posttranslational modification
Posttranslational modification is the chemical modification of a protein after its translation. It is one of the later steps in protein biosynthesis, and thus gene expression, for many proteins....

 such as phosphorylation.

See also

  • Negative electron-transfer dissociation
    Negative electron-transfer dissociation
    Negative electron-transfer dissociation is an ion/ion reaction in which an electron from an anionic specie is transferred to cationic reagent. Following this transfer event, the electron deficient anion undergoes internal rearrangement and fragments...

  • Tandem mass spectrometry
    Tandem mass spectrometry
    Tandem mass spectrometry, also known as MS/MS or MS2, involves multiple steps of mass spectrometry selection, with some form of fragmentation occurring in between the stages.-Tandem MS instruments:...

  • Electrospray
    Electrospray
    The name electrospray is used for a device that employs electricity to disperse a liquid or for the fine aerosol resulted in this process. The method is sometimes improperly called electrohydrodynamic atomization. High voltage is applied to a liquid supplied through an emitter...

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