Cation-specific interactions with carboxylate in amino acid and acetate aqueous solutions: X-ray absorption and ab initia calculations

Emad F. Aziz, Niklas Ottosson, Stefan Eisebitt, Wolfgang Eberhardt, Barbara Jagoda-Cwiklik, Robert Vácha, Pavel Jungwirth, Bernd Winter

Research output: Contribution to journalArticlepeer-review

153 Scopus citations

Abstract

Relative interaction strengths between cations (X = Li+, Na +, K+, NH4+) and anionic carboxylate groups of acetate and glycine in aqueous solution are determined. These model systems mimic ion pairing of biologically relevant cations with negatively charged groups at protein surfaces. With oxygen Is X-ray absorption spectroscopy, we can distinguish between spectral contributions from H 2O and carboxylate, which allows us to probe the electronic structure changes of the atomic site of the carboxylate group being closest to the countercation. From the intensity variations of the COO-aq O Is X-ray absorption peak, which quantitatively correlate with the change in the local partial density of states from the carboxylic site, interactions are found to decrease in the sequence Na+ > Li+ > K + > NR4+. This ordering, as well as the observed bidental nature of the -COO-aq and X +aq interaction, is supported by combined ab initio and molecular dynamics calculations.

Original languageEnglish
Pages (from-to)12567-12570
Number of pages4
JournalJournal of Physical Chemistry B
Volume112
Issue number40
DOIs
StatePublished - 9 Oct 2008
Externally publishedYes

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