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Determination of the microenvironment‐pH and charge and size characteristics of amino acids through their electrophoretic mobilities determined by CZE
Author(s) -
Piaggio Maria V.,
Peirotti Marta B.,
Deiber Julio A.
Publication year - 2007
Publication title -
electrophoresis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.666
H-Index - 158
eISSN - 1522-2683
pISSN - 0173-0835
DOI - 10.1002/elps.200700133
Subject(s) - electrophoresis , chemistry , amino acid , analyte , molecule , radius , hydrodynamic radius , charge (physics) , chemical physics , chromatography , analytical chemistry (journal) , organic chemistry , aqueous solution , biochemistry , physics , computer security , quantum mechanics , computer science , micelle
Abstract Effective electrophoretic mobility data of 20 amino acids reported in the literature are analyzed and interpreted through simple physicochemical models, which are able to provide estimates of coupled quantities like hydrodynamic shape factor, equivalent hydrodynamic radius (size), net charge, actual p K values of ionizing groups, partial charges of ionizing groups, hydration number, and pH near molecule (microenvironment‐pH of the BGE). It is concluded that the modeling of the electrophoretic mobility of these analytes requires a careful consideration of hydrodynamic shape coupled to hydration. In the low range of pH studied here, distinctive hydrodynamic behaviors of amino acids are found. For instance, amino acids with basic polar and ionizing side chain remain with prolate shape for pH values varying from 1.99 to 3.2. It is evident that as the pH increases from low values, amino acids get higher hydrations as a consequence each analyte total charge also increases. This result is consistent with the monotonic increase of the hydrodynamic radius, which accounts for both the analyte and the quite immobilized water molecules defining the electrophoretic kinematical unit. It is also found that the actual or effective p K value of the α‐carboxylic ionizing group of amino acids increases when the pH is changed from 1.99 to 3.2. Several limitations concerning the simple modeling of the electrophoretic mobility of amino acids are presented for further research.