title: Combined electron transfer dissociation-collision-induced dissociation fragmentation in the mass spectrometric distinction of leucine, isoleucine, and hydroxyproline residues in Peptide natural products.
abstract: Distinctions between isobaric residues have been a major challenge in mass spectrometric peptide sequencing. Here, we propose a methodology for distinction among isobaric leucine, isoleucine, and hydroxyproline, a commonly found post-translationally modified amino acid with a nominal mass of 113 Da, through a combined electron transfer dissociation-collision-induced dissociation approach. While the absence of c and z(•) ions, corresponding to the Yyy-Xxx (Xxx = Leu, Ile, or Hyp) segment, is indicative of the presence of hydroxyproline, loss of isopropyl (Δm = 43 Da) or ethyl radicals (Δm = 29 Da), through collisional activation of z radical ions, are characteristic of leucine or isoleucine, respectively. Radical migration processes permit distinctions even in cases where the specific z(•) ions, corresponding to the Yyy-Leu or -Ile segments, are absent or of low intensity. This tandem mass spectrometric (MS(n)) method has been successfully implemented in a liquid chromatography-MS(n) platform to determine the identity of 23 different isobaric residues from a mixture of five different peptides. The approach is convenient for distinction of isobaric residues from any crude peptide mixture, typically encountered in natural peptide libraries or proteomic analysis.
authors: Molecular Biophysics Unit, Indian Institute of Science , Bangalore 560012, India.
authors: Kallol
authors: K
authors: Gupta
authors: Mukesh
authors: M
authors: Kumar
authors: Krishnappa
authors: K
authors: Chandrashekara
authors: Kozhalmannom S
authors: KS
authors: Krishnan
authors: Padmanabhan
authors: P
authors: Balaram
mesh_terms: D000595:Amino Acid Sequence; D001688:Biological Products / Q000737:chemistry*; D006909:Hydroxyproline / Q000737:chemistry*; D007532:Isoleucine / Q000737:chemistry*; D007930:Leucine / Q000737:chemistry*; D013058:Mass Spectrometry / Q000379:methods*; D008555:Melitten / Q000737:chemistry; D008969:Molecular Sequence Data; D054848:Peptaibols / Q000737:chemistry; D010455:Peptides / Q000737:chemistry*; D020539:Sequence Analysis, Protein / Q000379:methods*; D014862:Wasp Venoms / Q000737:chemistry
chemical_list: D001688:Biological Products; D054848:Peptaibols; D010455:Peptides; D014862:Wasp Venoms; D007532:Isoleucine; C006596:antiamoebin; D008555:Melitten; C077077:zervamicin IIB; D007930:Leucine; D006909:Hydroxyproline