Distinction and quantitation of leucine-isoleucine isomers and lysine-glutamine isobars by electrospray ionization tandem mass spectrometry (MSn,n = 2, 3) of copper(II)-diimine complexes
✍ Scribed by Seymour, Jennifer L.; Turecek, Frantisek
- Publisher
- John Wiley and Sons
- Year
- 2000
- Tongue
- English
- Weight
- 121 KB
- Volume
- 35
- Category
- Article
- ISSN
- 1076-5174
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✦ Synopsis
Electrospray ionization of mixtures of isomeric and isobaric amino acids was investigated with the goal of distinguishing and quantifying the components. Isomeric amino acids leucine and isoleucine were readily distinguished and quantified in 90 : 10 to 10 : 90 binary mixtures using two-stage (MS 2 ) and three-stage (MS 3 ) tandem mass spectrometric dissociations of ternary Cu 2Y -2,2 -bipyridyl (bpy) complexes, [Cu(AA -H)bpy] Y . The complexes self-assembled in solution upon mixing the components and provided a convenient means of efficient derivatization that increased the efficiency of amino acid ionization by electrospray and shifted the mass of the analytes to a region which was free of solvent interferences. Low-energy dissociations of [Cu(AA -H)bpy] Y complexes in a quadrupole ion trap were achieved at >90% conversions and >80% trapping efficiencies for the MS 2 and MS 3 precursor and fragment ions. Isobaric amino acids glutamine and lysine were also distinguished through MS 2 and MS 3 of their ternary complexes with Cu 2Y and bpy. ESI of [Cu(Gln -H)bpy] Y was enhanced in the presence of [Cu(Lys -H)bpy] Y , which resulted in non-linear response at low Lys concentrations.