Generation of peptide radical dications via low-energy collision-induced dissociation of [CuII(terpy)(M + H)].3+

J Am Soc Mass Spectrom. 2005 Nov;16(11):1795-804. doi: 10.1016/j.jasms.2005.06.015. Epub 2005 Sep 29.

Abstract

The first example of the formation of hydrogen-deficient radical cations of the type [M + H](.2+) is demonstrated to occur through a one-electron-transfer mechanism upon low-energy collision-induced dissociation (CID) of gas-phase triply charged [Cu(II)(terpy)(M + H)](.3+) complex ions (where M is an angiotensin III or enkephalin derivative; terpy = 2,2':6',2''-terpyridine). The collision-induced dissociation of doubly charged [M + H](.2+) radical cations generates similar product ions to those prepared through hot electron capture dissociation (HECD). Isomeric isoleucine and leucine residues were distinguished by observing the mass differences between [z(n) + H](.+) and w(n)(+) ions (having the same residue number, n) of the Xle residues. The product ion spectrum of [z(n) + H](.+) reveals that the w(n)(+) ions are formed possibly from consecutive fragmentations of [z(n) + H](.+) ions. Although only the first few [M + H](.2+) species have been observed using this approach, these hydrogen-deficient radical cations produce fragment ions that have more structure-informative patterns and are very different from those formed during the low-energy tandem mass spectrometry of protonated peptides.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acids / analysis
  • Amino Acids / chemistry
  • Angiotensins / analysis*
  • Angiotensins / chemistry*
  • Copper / analysis
  • Copper / chemistry*
  • Energy Transfer
  • Free Radicals / chemistry
  • Peptides / analysis*
  • Peptides / chemistry*
  • Pyridines / analysis
  • Pyridines / chemistry*
  • Spectrometry, Mass, Electrospray Ionization / methods*

Substances

  • Amino Acids
  • Angiotensins
  • Free Radicals
  • Peptides
  • Pyridines
  • Copper