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Issue 4, 2000
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Zwitterionic vs. charge-solvated structures in the binding of arginine to alkali metal ions in the gas phase

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Abstract

The relative alkali metal ion (M+) affinities between a side-chain functionalized amino acid in its canonical form (free acid) and the corresponding methyl ester (M = Li, Na, K, Cs), and between a zwitterionic amino acid and isomeric alkyl esters (M = Na), are determined in the gas phase based on the dissociation of A1–M+–A2 heterodimers, in which A1 and A2 represent ester and/or amino acid ligands (kinetic method). With all dimers studied, the affinities increase in the order free acid < ester < zwitterion. With this information at hand, the M+ affinities of arginine, which may bind M+ as a free acid or as a zwitterion, are compared with those of arginine methyl ester, which cannot form a zwitterion, and with those of the amino acid betaine, a permanent zwitterion. These experiments indicate that the Li+ and Na+ complexes contain the free acid form of arginine (charge solvation), whereas the complexes with the larger K+ and Cs+ ions contain zwitterionic arginine (salt bridge).

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Publication details

The article was received on 22 Nov 1999, accepted on 07 Feb 2000 and first published on 08 Mar 2000


Article type: Paper
DOI: 10.1039/A909220J
Analyst, 2000,125, 657-660

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    Zwitterionic vs. charge-solvated structures in the binding of arginine to alkali metal ions in the gas phase

    B. A. Cerda and C. Wesdemiotis, Analyst, 2000, 125, 657
    DOI: 10.1039/A909220J

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