Quantitation and Improved de Novo Sequencing of Proteins by Isotopic N-Terminal Labeling of Peptides with a Multifunctional Charged Tag

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Weibin Chen, Peter J. Lee, Daniel B. Wall,Ying-Qing Yu, John C. Gebler [Waters]
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Fibrogen Peptide A
A method for comparative quantitation and de novo peptide sequencing of proteins in MALDI analysis is described. The approach is based on a simple and efficient coupling reaction to derivatize peptides/protein digests with a multifunctional charged tag. The mass spectra of derivatized digests exhibit more intense peaks than their underivatized counterparts, increasing the information obtained in peptide mapping experiment. Since the reagent carries a fixed positive charge and labels only the N-terminal of peptides, the fragmentation of derivatized peptides in MALDI MS/MS settings (Q-TOF) follows different pathways from native species, yielding primarily an easily interpretable series of a/b-ions. Furthermore, this labeling strategy also enables relative quantitation studies as a stable isotopic form of the reagent can readily be synthesized.

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