Collision-activated dissociation , peptide

N. Sadagopan, M. Malone, and J. T. Watson, Effect of charge derivatization in the determination of phosphorylation sites in peptides by electrospray ionization collision-activated dissociation tandem mass spectrometry, 7. Mass Spectrom. 34, 1279-1282 (1999). 

Yates, N. Kottmeier, D. Shabanowitz, J. Hunt, D. Multi-stage collision activated dissociation of protonated peptides by electrospray/quadrupole ion trap mass spectrometry. Proceedings of the 42nd ASMS Conference on Mass Spectrometry and Allied Topics, Chicago, IL, May 29-June 3, 1994, p. 212. 

Modem mass spectrometric methods greatly help to speed up degradation studies by identifying the molecular mass of peptide fragments. Various desorption techniques, which produce protonated protein ions in the gas phase, are applied. Prominent examples are fast-atom bombardment (FAB) and matrix- assisted laser desorption/ionization (MALDI). Most commonly these techniques provide only the mass of the molecular ion, but they can be coupled with a collision-induced dissociation (CID) procedure. The ions are activated by collisions with neutral target gases, and the peptides dissociate in the gas phase. The resulting mass spectra... 

In addition, new tandem mass spectrometry technologies were also among the important innovations. Apart from traditional collision-induced dissociation (CID) [89-91], a variety of activation methods (used to add energy to mass-selected ions) based on inelastic collisions and photon absorption have been widely utilized. They include IR multiphoton excitation [92,93], UV laser excitation [94—97], surface-induced dissociation (SID) [98-100], black body radiation (101, 102], thermal dissociation [103], and others. As the fragmentation of peptide/protein ions is a central topic in proteomics, there is strong interest in such novel ion dissociation methods as electron capture dissociation (ECD) [104, 105] and electron transfer dissociation [22]. These new methods can provide structural information that complements that obtained by traditional collisional activation. Also, very recently, ambient ion dissociation methods such as atmospheric pressure thermal dissociation [106] and low temperature plasma assisted ion dissociation [107] have been reported. 

FT-ICR instruments are also capable of performing MS" experiments. The most popular method of ion activation is sustained off-resonance irradiation (SORI), where ions are excited to a larger cyclotron radius using rf energy, undergo collisions with a neutral gas pulsed into the cell and dissociate. Other methods are available, including infrared multiphoton dissociation (IRMPD)65 and electron capture dissociation (ECD)66 which is of particular value in glyco-peptide analysis (Section VIA). 

Mass analysis determines the mass-to-charge ratio (tn/z) of ions derived from the analyte. For peptide ions, two characteristics can be obtained. The first characteristic is the molecular weight of the peptide, which can be calculated from the measured m/z of the source-generated intact peptide ion (the so-called molecular ion). The second characteristic is structural information that is obtained via an MS/MS analysis. An MS/MS experiment measures gas-phase dissociations of an activated molecular ion of the peptide to yield product-ion data that are diagnostic of the peptide sequence. The basic sequence of events in MS/MS includes 1. mass selection of the peptide ion of interest (that is population of ions of a single m/z) as a so-called precursor ion 2. activation of the precursor ion, most commonly through collisions with an inert gas, followed by dissociation of the activated precursor and formation of product ions 3. mass... 

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