title: Fragmentations of [M-H]- anions of peptides containing tyrosine sulfate. Does the sulfate group rearrange? A joint experimental and theoretical study.
abstract: BACKGROUND
  To investigate the fragmentations in the negative-ion electrospray mass spectra of peptides containing tyrosine sulfate.
  
  
  METHODS
  Possible fragmentation mechanisms were explored using a Waters QTOF2 tandem mass spectrometer in concert with calculations at the CAM-B3LYP/6-311++g(d,p) level of theory.
  
  
  RESULTS
  The major negative ion formed in the ESI-MS of peptides containing tyrosine sulfate is [(M-H)-SO3](-) and this process normally yields the base peak of the spectrum. The basic backbone cleavages of [(M-H)-SO3](-) allowed the sequence of the peptide to be determined. Rearrangement reactions involving the formation of HOSO3(-) and [(M-H)-H2SO4](-) yielded minor peaks with relative abundances ≤ 10% and ≤ 2%, respectively.
  
  
  CONCLUSIONS
  The mass spectra of the [M-H](-) and [(M-H)-SO3](-) anions of peptides containing tyrosine sulfate allowed the position of the tyrosine sulfate group to be determined, together with the amino acid sequence of the peptide.
authors.affiliation: Department of Chemistry, The University of Adelaide, South Australia, Australia.
authors.forename: T T Nha
authors.initials: TT
authors.lastname: Tran
authors.forename: Tianfang
authors.initials: T
authors.lastname: Wang
authors.forename: Sandra
authors.initials: S
authors.lastname: Hack
authors.forename: John H
authors.initials: JH
authors.lastname: Bowie
mesh_terms: D000595:Amino Acid Sequence; D000838:Anions / Q000737:chemistry*; D008962:Models, Theoretical; D010446:Peptide Fragments / Q000737:chemistry*; D011522:Protons; D021241:Spectrometry, Mass, Electrospray Ionization; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000737:chemistry
chemical_list: D000838:Anions; D010446:Peptide Fragments; D011522:Protons; C005662:tyrosine O-sulfate; D014443:Tyrosine