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Type: Artigo de periódico
Title: Isomeric differentiation and quantification of alpha, beta-amino acid-containing tripeptides by the kinetic method: alkali metal-bound dimeric cluster ions
Author: Wu, LM
Meurer, EC
Young, B
Yang, PX
Eberlin, MN
Cooks, RG
Abstract: The kinetic method is applied to differentiate and quantify mixtures of isomeric tripeptides by generating and mass-selecting alkali metal ion-bound dimeric clusters and examining their competitive dissociations in an ion trap mass spectrometer. This methodology readily distinguishes the pairs of isomers examined here: (alpha-A)GG/(beta-A)GG, G(alpha-A)G/G(beta-A)G, and GG(alpha-A)/GG(beta-A). The isomeric selectivity increases with decreasing size of the metal ion, viz. from Cs to Rb to K to Na to Li. When alanine is at the N-terminus, as in the case of (alpha-A)GG/(beta-A)GG, the isomeric selectivity can exceed 10(3). The corresponding proton-bound dimers behave similarly to the Li clusters. Structural features that favor zwitterionic versus charge-solvated forms of the alkali metal-bound clusters are reflected in the b(n) and y(n) fragment ion abundances recorded by tandem mass spectrometry, and the propensities to form the charge-solvated or zwitterionic structures play a key role in promoting isomeric differentiation. The zwitterionic forms favor intramolecular interactions in the cluster and hence isomeric distinction. There is no discrimination in the formation of the alkali metal-bound dimers, so isomeric quantification is based entirely on dissociation kinetics. Previous kinetic method-based isomeric analyses have used the trimeric clusters and shown linear correlations between composition of the mixture of isomers and the logarithm of the branching ratio for competitive fragmentation. A similar relationship is found for the dimeric clusters examined here. As used here, the kinetic method provides a possible way for future quantitative analysis of mixtures of larger peptides such as those generated in combinatorial synthesis of peptides and peptide mimics. (C) 2004 Elsevier B.V. All rights reserved.
Subject: kinetic method
isomeric tripeptides
central ion effects
Country: Holanda
Editor: Elsevier Science Bv
Citation: International Journal Of Mass Spectrometry. Elsevier Science Bv, v. 231, n. 41700, n. 103, n. 111, 2004.
Rights: fechado
Identifier DOI: 10.1016/j.ijms.2003.09.017
Date Issue: 2004
Appears in Collections:Unicamp - Artigos e Outros Documentos

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