Determination of Peptide Topology through Time-Resolved Double-Resonance under Electron Capture Dissociation Conditions

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• 作者：Marie P茅rot-Taillandier ; S茅verine Zirah ; Sylvie Rebuffat ; Uwe Linne ; Mohamed A. Marahiel ; Richard B. Cole ; Jean-Claude Tabet ; Carlos Afonso
• 刊名：Analytical Chemistry
• 出版年：2012
• 出版时间：June 5, 2012
• 年：2012
• 卷：84
• 期：11
• 页码：4957-4964
• 全文大小：564K
• 年卷期：v.84,no.11(June 5, 2012)
• ISSN：1520-6882

文摘

Characterizing the conformation of biomolecules by mass spectrometry still represents a challenge. With their knotted structure involving a N-terminal macrolactam ring where the C-terminal tail of the peptide is threaded and sterically trapped, lasso peptides constitute an attractive model for developing methods for characterizing gas-phase conformation, through comparison with their unknotted topoisomers. Here, the kinetics of electron capture dissociation (ECD) of a lasso peptide, capistruin, was investigated by electrospray ionization-Fourier transform ion cyclotron resonance mass spectrometry and compared to that of its branched-cyclic topoisomer, lactam-capistruin. Both peptides produced rather similar ECD spectra but showed different extent of H^{鈥?/sup> transfer from c_i藞 to z_j鈥?/sup> ions. Time-resolved double-resonance experiments under ECD conditions were performed to measure the formation rate constants of typical product ions. Such experiments showed that certain product ions, in particular those related to H鈥?/sup> transfer, proceeded through long-lived complexes for capistruin, while fast dissociation processes predominated for lactam-capistruin. The formation rate constants of specific ECD product ions enabled a clear differentiation of the lasso and branched-cyclic topoisomers. These results indicate that the formation kinetics of ECD product ions constitute a new way to explore the conformation of biomolecules and distinguish between topoisomers and, more generally, conformers.}