title: Generation of peptide radical dications via low-energy collision-induced dissociation of [CuII(terpy)(M + H)].3+ .
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.
authors.affiliation: Department of Chemistry, The University of Hong Kong, Hong Kong, China. ivankchu@hku.hk
authors.forename: Ivan K
authors.initials: IK
authors.lastname: Chu
authors.forename: Corey N W
authors.initials: CN
authors.lastname: Lam
mesh_terms: D000596:Amino Acids / Q000032:analysis / Q000737:chemistry; D000809:Angiotensins / Q000032:analysis* / Q000737:chemistry*; D003300:Copper / Q000032:analysis / Q000737:chemistry*; D004735:Energy Transfer; D005609:Free Radicals / Q000737:chemistry; D010455:Peptides / Q000032:analysis* / Q000737:chemistry*; D011725:Pyridines / Q000032:analysis / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*
chemical_list: D000596:Amino Acids; D000809:Angiotensins; D005609:Free Radicals; D010455:Peptides; D011725:Pyridines; D003300:Copper