Rb+ and Na+ spin relaxation in aqueous gellan solutions and implication of selective site binding of alkali metal ions

M. Annaka, R. Takahashi, T. Nakahira, Masayuki Tokita, T. Matsuura

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)

Abstract

87Rb NMR was applied to investigate the site binding of Rb+ ions in gellan gum gels. The temperature dependence of the transverse and longitudinal relaxation NMR relaxation rates of 87Rb+ ion and 23Na+ ion have been compared in aqueous 5% (w/v) rubidium-type and sodium-type gellan. In each sample, the relaxation rates were sensitive to the conformation (helix or random coil). In rubidium-type gellan, significant line-broadening effects (losses in intensity) were found, which is due to the presence of cation-binding sites in the ordered conformation. In sodium-type gellan, such an enhancement of the relaxation was not observed. These results indicated that gellan gum produced highly selective binding sites for alkali metal ions, in which Rb+ ion bound more strongly than Na+ ion. The 87Rb NMR line shift suggested selective site binding of ions to form the cross-linking domains in gellan gels.

Original languageEnglish
Pages (from-to)635-640
Number of pages6
JournalBiomacromolecules
Volume2
Issue number3
DOIs
Publication statusPublished - Oct 4 2001

All Science Journal Classification (ASJC) codes

  • Bioengineering
  • Biomaterials
  • Polymers and Plastics
  • Materials Chemistry

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