Collision-induced dissociation

Collision-induced dissociation (CID), also known as collisionally activated dissociation (CAD), is a mass spectrometry technique to induce fragmentation of molecular ions in the gas phase.[1][2] The molecular ions are usually accelerated by some electrical potential to high kinetic energy and then allowed to collide with neutral molecules (often helium, nitrogen or argon). In the collision some of the kinetic energy is converted into internal energy which results in bond breakage and the fragmentation of the molecular ion into smaller fragments. These fragment ions can then be analyzed by a tandem mass spectrometry.

CID and the fragment ions produced by CID are used for several purposes. Partial or complete structural determination can be achieved. In some cases identity can be established based on previous knowledge without determining structure. Another use is in simply achieving more sensitive and specific detection. By detecting a unique fragment ion, the precursor ion can be detected in the presence of other ions of the mass to charge ratio, reducing the background and increasing the limit of detection.

Triple quadrupole mass spectrometers

In a triple quadrupole mass spectrometer there are three quadrupoles. The first quadrupole termed "Q1" can act as a mass filter and transmits a selected ion and accelerates it towards "Q2" which is termed a collision cell. The pressure in Q2 is higher and the ions collides with neutral gas in the collision cell and fragments by CID. The fragments are then accelerated out of the collision cell and enter Q3 which scans through the mass range, analyzing the resulting fragments (as they hit a detector). This produces a mass spectrum of the CID fragments from which structural information or identity can be gained. Many other experiments using CID on a triple quadrupole exist such as precursor ion scans that determines where a specific fragment came from rather than what fragments are produced by a given molecule.

Fourier transform ion cyclotron resonance

Sustained off-resonance irradiation collision-induced dissociation (SORI-CID) is a CID technique used in Fourier transform ion cyclotron resonance mass spectrometry which involves accelerating the ions in cyclotron motion (in a circle inside of an ion trap) and then increasing the pressure resulting collisions that produce CID fragments.[3]

Higher-energy collisional dissociation

Higher-energy collisional dissociation (HCD) is a CID technique specific to the orbitrap mass spectrometer in which fragmentation takes place external to the trap.[4] HCD was formerly known as higher-energy C-trap dissociation. In HCD, the ions pass through the C-trap and into the HCD cell, an added multipole collision cell, where dissociation takes place. The ions are then returned to the C-trap before injection into the orbitrap for mass analysis. HCD does not suffer from the low mass cutoff of resonant-excitation (CID) and therefore is useful for isobaric tag–based quantification as reporter ions can be observed. Despite the name, the collision energy of HCD is typically in the regime of low energy collision induced dissociation (less than 100 eV).[4][5]

Fragmentation mechanisms

Homolytic fragmentation

Homolytic fragmentation is bond dissociation where each of the fragments retains one of the originally-bonded electrons.[6]

Heterolytic fragmentation

Heterolytic fragmentation is bond cleavage where the bonding electrons remain with only one of the fragment species.[7]

In CID, charge remote fragmentation is a type of covalent bond breaking that occurs in a gas phase ion in which the cleaved bond is not adjacent to the location of the charge.[8][9] This fragmentation can be observed using tandem mass spectrometry.[10]

See also

References

  1. ↑ Wells JM, McLuckey SA (2005). "Collision-induced dissociation (CID) of peptides and proteins". Meth. Enzymol. 402: 148–85. doi:10.1016/S0076-6879(05)02005-7. PMID 16401509.
  2. ↑ Sleno L, Volmer DA (2004). "Ion activation methods for tandem mass spectrometry". Journal of mass spectrometry : JMS 39 (10): 1091–112. doi:10.1002/jms.703. PMID 15481084.
  3. ↑ Laskin, Julia; Futrell, Jean H. (2005). "Activation of large lons in FT-ICR mass spectrometry". Mass Spectrometry Reviews 24 (2): 135–167. doi:10.1002/mas.20012. ISSN 0277-7037. PMID 15389858.
  4. 1 2 Olsen JV, Macek B, Lange O, Makarov A, Horning S, Mann M (September 2007). "Higher-energy C-trap dissociation for peptide modification analysis". Nat. Methods 4 (9): 709–12. doi:10.1038/nmeth1060. PMID 17721543.
  5. ↑ Murray, Kermit K.; Boyd, Robert K.; Eberlin, Marcos N.; Langley, G. John; Li, Liang; Naito, Yasuhide (2013). "Definitions of terms relating to mass spectrometry (IUPAC Recommendations 2013)". Pure and Applied Chemistry 85 (7). doi:10.1351/PAC-REC-06-04-06. ISSN 1365-3075.
  6. ↑ IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version:  (2006–) "homolysis (homolytic)".
  7. ↑ IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version:  (2006–) "heterolysis (heterolytic)".
  8. ↑ Cheng C, Gross ML (2000), "Applications and mechanisms of charge-remote fragmentation", Mass Spectrom Rev 19 (6): 398–420, doi:10.1002/1098-2787(2000)19:6<398::AID-MAS3>3.0.CO;2-B, PMID 11199379.
  9. ↑ Gross, M. (2000), "Charge-remote fragmentation: an account of research on mechanisms and applications", International Journal of Mass Spectrometry 200 (1-3): 611, Bibcode:2000IJMSp.200..611G, doi:10.1016/S1387-3806(00)00372-9
  10. ↑ "Remote-site (charge-remote) fragmentation", Rapid Communications in Mass Spectrometry 2 (10), 1988: 214, doi:10.1002/rcm.1290021009
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