- Electron capture dissociation
In
mass spectrometry , electron capture dissociation (ECD) is a method of fragmenting gas phase ions for tandem mass spectrometric analysis (structural elucidation). ECD involves the direct introduction of low energy electrons to trapped gas phase ions. [Zubarev, R. A.; Kelleher, N. L.; McLafferty, F. W. Electron Capture Dissociation of Multiply Charged Protein Cations - a Nonergodic Process "J. Am. Chem. Soc." 1998, "120", 3265-3266.]Principles
Electron capture dissociation typically involves a multiply protonated molecule "M" interacting with a free electron to form an odd-electron ion
:.
Liberation of the
electric potential energy results in fragmentation of the product ion.ECD produces significantly different types of fragment ions than other fragmentation methods such as
collision-induced dissociation andinfrared multiphoton dissociation . These other methods introduce internal vibrational energy in some way or another while ECD does not. The unique (and complementary) fragments observed and the ability to fragment whole macromolecules effectively has been promising. The low efficiencies and other experimental difficulties have prevented wide spread use. ECD is primarily used inFourier transform ion cyclotron resonance mass spectrometry.cite journal |author=Cooper HJ, Håkansson K, Marshall AG |title=The role of electron capture dissociation in biomolecular analysis |journal=Mass spectrometry reviews |volume=24 |issue=2 |pages=201–22 |year=2005 |pmid=15389856 |doi=10.1002/mas.20014]ECD is a recently introduced technique and is still being investigated. [cite journal |author=Syrstad EA, Turecek F |title=Toward a general mechanism of electron capture dissociation |journal=J. Am. Soc. Mass Spectrom. |volume=16 |issue=2 |pages=208–24 |year=2005 |pmid=15694771 |doi=10.1016/j.jasms.2004.11.001] [cite journal |author=Savitski MM, Kjeldsen F, Nielsen ML, Zubarev RA |title=Complementary sequence preferences of electron-capture dissociation and vibrational excitation in fragmentation of polypeptide polycations |journal=Angew. Chem. Int. Ed. Engl. |volume=45 |issue=32 |pages=5301–3 |year=2006 |pmid=16847865 |doi=10.1002/anie.200601240] 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. Suggestions have been made that radical reactions initiated by the electron may be responsible for the action of ECD.Fact|date=October 2007
In a similar technique called
electron transfer dissociation the electrons are transferred by collision between the analyte cations and anions.ee also
*
RRKM theory External links
* [http://www.ionspec.com/FTMS%20Tutorial/FTMS%20Tutorial%20Pt%204/tutorial%20pt4_info.htm A tutorial on tandem FTMS including ECD]
References
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