Electron-capture dissociation technique

Other fragmentation techniques have been introduced [108]. Some of these, e.g., sustained off-resonance irradiation (SORl) and infrared multiphoton dissociation (IRMPD), provide similar fragmentation as in CID, i.e., preferential backbone cleavages at the peptide amide bond (b- and y-ions). Others like electron-capture dissociation (ECD) [109-110] induce different fragmentation reactions, i.e., the formation of c- and z -ions due to cleavage of N-C bonds. 

The following ion-activation techniques have been used at one time or other to sequence peptides (1) fast atom bombardment (FAB) ionization, (2) CID—tandem MS (MS/MS), (3) ESI in-source CID, (4) MALDI ion-source decay, (5) MALDI postsource decay (PSD), (6) electron-capture dissociation (ECD) and electron-transfer dissociation, and (7) peptide ladder sequencing. Because of the lack of space, only (2) and (4) will be discussed further. 

Fragmentation of peptide and protein ions in FT-ICR mass spectrometry may be induced by sustained off-resonance irradiation collision-induced dissociation (SORI-CID) [28], infrared multiphoton dissociation (IRMPD) [29,30], blackbody infrared radiative dissociation (BIRD) [31,32], surface-induced dissociation (SID) [33,34], and electron capture dissociation (ECD) [35,36]. These techniques are true MS/MS techniques in which the precursor ion is isolated prior to fragmentation. Additional techniques in which ions are not isolated but fragmented before they... 

Another dissociation technique that has been applied to large multiply charged ions is electron-capture dissociation (ECD), in which precursor ions capture a low-energy electron to produce an intermediate that rapidly dissociates. In some cases, a background gas is added to aid in the dissociation process. 

The configuration and reactivity of methyl radical-cyanide ion pairs produced by dissociative electron capture in the two solid phases of CH3CN have been studied by e.s.r. techniques using CD313CN.103 The results indicate that the radical configuration is planar and that the reactivity of the radical (as estimated from hydrogen-abstraction rates) in crystal I is at least 10 times greater than in crystal II. 

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