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Relative calcium‐binding strengths of amino acids determined using the kinetic method
Author(s) -
Ho YenPeng,
Yang MingWei,
Chen LiTing,
Yang YuChuan
Publication year - 2007
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.2927
Subject(s) - chemistry , amino acid , calcium , dissociation (chemistry) , divalent , ion , metal ions in aqueous solution , kinetic energy , stereochemistry , crystallography , biochemistry , organic chemistry , physics , quantum mechanics
We have measured the relative calcium‐binding energies of amino acids using tandem mass spectrometry of Ca 2+ ‐bound trimeric amino acids. Although calcium‐bound dimeric amino acid complexes coordinated too strongly to allow observation of the two competing dissociation products (calcium‐bound monomeric ions) required for analysis of their metal binding affinities using the conventional kinetic method, the Ca 2+ ‐bound trimeric cluster ions dissociated readily to form dimeric cluster ions through simple ligand losses. The calcium‐binding energies were obtained by comparing the ratio of the [Ca 2+ (A 1 ) 2 H + ] + and [Ca 2+ (A 1 )(A 2 ) H + ] + ions that dissociated from the [Ca 2+ (A 1 ) 2 (A 2 ) H + ] + ion and the ratio of the [Ca 2+ (A 2 ) 2 H + ] + and [Ca 2+ (A 1 ) (A 2 ) H + ] + ions that dissociated from the [Ca 2+ (A 1 )(A 2 ) 2 H + ] + ion, where A 1 and A 2 represent two amino acids. The energies deduced from this analysis represent the relative average binding energies of complexes having the form [Ca 2+ (A 1 ) 2 H + ] + . The relative Ca 2+ ‐binding strengths of the α ‐amino acid complexes follow the order Cys < Ser < Thr < Ile < Leu < Val < Gly < Ala < Pro < Phe < Met < Tyr < Asn < His < Gln < Trp < Lys < Arg. To our knowledge, this report provides the first example of using kinetic methods to determine the relative binding strengths of divalent metal–amino acid complexes. Copyright © 2007 John Wiley & Sons, Ltd.