Conformation and persistence length of chitosan in aqueous solutions of different ionic strengths via asymmetric flow field-flow fractionation

Yu Kang; Xinyue Zhao; Xintong Han; Xiangling Ji; Quan Chen; Harald Pasch; Albena Lederer; Yonggang Liu

doi:10.1016/j.carbpol.2021.118402

Conformation and persistence length of chitosan in aqueous solutions of different ionic strengths via asymmetric flow field-flow fractionation

Carbohydr Polym. 2021 Nov 1:271:118402. doi: 10.1016/j.carbpol.2021.118402. Epub 2021 Jul 5.

Authors

Yu Kang¹, Xinyue Zhao¹, Xintong Han², Xiangling Ji¹, Quan Chen¹, Harald Pasch³, Albena Lederer⁴, Yonggang Liu⁵

Affiliations

¹ State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China; University of Science and Technology of China, Hefei 230026, China.
² State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China.
³ Department of Chemistry and Polymer Science, University of Stellenbosch, Private Bag X1, 7602 Matieland, South Africa.
⁴ Department of Chemistry and Polymer Science, University of Stellenbosch, Private Bag X1, 7602 Matieland, South Africa; Leibniz-Institut für Polymerforschung Dresden e.V., 01069 Dresden, Germany.
⁵ State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China. Electronic address: yonggang@ciac.ac.cn.

PMID: 34364548
DOI: 10.1016/j.carbpol.2021.118402

Abstract

Conformation of chitosan in acidic aqueous solutions is strongly influenced by ionic strength, but the conventional employed size exclusion chromatography is limited to high ionic strength. Here we show that conformation of chitosan in acetate buffer down to millimolar ionic strength can be studied via asymmetric flow field-flow fractionation (AF4), where the separation is governed by the diffusion properties of the chitosan molecules and assisted by the electrostatic repulsion of the polyelectrolyte from the channel membrane. The size of chitosan decreases with ionic strength due to increasing screening of the polyelectrolyte effect. The persistence length of chitosan in the solutions, obtained by fitting the conformation plot by the wormlike chain model, decreases linearly with the Debye screening length from 44.5 nm at a salt concentration of 1.25 mM dominated by the electrostatic contribution to 8.6 nm in 800 mM acetate buffer close to its intrinsic persistence length of 7.7 nm.

Keywords: Chitosan; Conformation; Field-flow fractionation; Ionic strength; Persistence length; Polyelectrolyte.