The significance of monoisotopic and carbon-13 isobars for the identification of a 19-component dodecapeptide library by positive ion electrospray Fourier transform ion cyclotron resonance mass spectrometry.
Harnessing the ultra high resolution capabilities of Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) and positive ion electrospray, we have demonstrated the significance and utility of cumulative mass defect high resolution mass separation stable isotope distribution, exact mass measurement and elemental formula as a means of simultaneously identifying 19 components of the dodecapeptide library Ac-ANKISYQS[X]STE-NH(2). With an instrument resolution of 275 000 (average), isobaric multiplets attributed to monoisotopic and carbon-13 components of peptides: Ac approximately SLS approximately NH(2); Ac approximately SNS approximately NH(2); Ac approximately SOS approximately NH(2); Ac approximately SDS approximately NH(2); within the mass window of 1380-1385 Da, and Ac approximately SQS approximately NH(2); Ac approximately SKS approximately NH(2); Ac approximately SES approximately NH(2); Ac approximately SMS approximately NH(2), within the mass window 1395-1400 Da, were mass resolved, accurately mass measured and identified from the computed molecular formulas. This experimental procedure enabled the separation of monoisotopic and carbon-13 isobars yielding enhanced selectivity and specificity and serves to illustrate the significance of monoisotopic and carbon-13 isobars in final product analysis. Chromatographic separation (HPLC) was of limited utility except for monitoring the overall extent of reaction and apparent product distribution. Positive ion electrospray-FTICR-MS and fast atom bombardment (FAB) MS were used to assess final product quality and apparent component distribution.
Department of Medicinal Chemistry, Merck Research Laboratories, West Point, PA 19486, USA.
H G
HG
Ramjit
G H
GH
Kruppa
J P
JP
Spier
C W
CW
Ross
V M
VM
Garsky
D002247:Carbon Isotopes; D002851:Chromatography, High Pressure Liquid; D017357:Cyclotrons; D010450:Endopeptidases; D005583:Fourier Analysis; D006868:Hydrolysis; D019151:Peptide Library; D010455:Peptides / Q000032:analysis* / Q000302:isolation & purification; D016339:Spectrometry, Mass, Fast Atom Bombardment
D002247:Carbon Isotopes; D019151:Peptide Library; D010455:Peptides; D010450:Endopeptidases