The effect of the linear charge density of carrageenan on the ion binding investigated by differential scanning calorimetry, dc conductivity, and kHz dielectric relaxation

Makoto Takemasa, Katsuyoshi Nishinari

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

The effect of the linear charge density of natural polyelectrolyte, carrageenan, on the ion binding to carrageenan molecules in relation to the gelation was investigated by using the dielectric relaxation spectroscopy, dc conductivity, optical rotation, and differential scanning calorimetry (DSC). Although carrageenan is an anionic polysaccharide, carrageenan molecules in the helix state at low temperatures can bind not only cation, such as potassium and cesium, but also anion, such as iodide. The dc conductivity steeply decreases just below the coil-helix transition temperature, which indicates the binding of ion to the carrageenan molecules in the helix state due to the increase of the linear charge density compared with that in the coil state. The addition of NaI promotes the helix formation, and prevents from aggregation of helices, which was suggested by the results of the dynamic shear modulus and the DSC, and resulted in an increase of the relaxation amplitude of the lowest frequency relaxation (∼kHz) attributed to the fluctuation of the tightly bound counter ions along the high charge density region (helix). It is concluded that binding of iodide induces (1) the increase in the amount of tightly bound counterions to carrageenan molecules and (2) the formation of non-aggregated helix.

Original languageEnglish
Pages (from-to)231-240
Number of pages10
JournalColloids and Surfaces B: Biointerfaces
Volume38
Issue number3-4 SPEC. ISS.
DOIs
Publication statusPublished - 2004 Nov 15
Externally publishedYes

Keywords

  • Carrageenan gel
  • dc conductivity
  • Dielectric relaxation spectroscopy
  • Differential scanning calorimetry
  • Optical rotation

ASJC Scopus subject areas

  • Biotechnology
  • Colloid and Surface Chemistry
  • Physical and Theoretical Chemistry
  • Surfaces and Interfaces

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