These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Anomalous stiffening and ion-induced coil-helix transition of carrageenans under monovalent salt conditions.
    Author: Schefer L, Usov I, Mezzenga R.
    Journal: Biomacromolecules; 2015 Mar 09; 16(3):985-91. PubMed ID: 25686463.
    Abstract:
    The macromolecular conformations of anionic polysaccharides with decreasing linear charge densities—lambda, iota, and kappa carrageenan—, at varying NaCl concentrations, are studied by single-chain statistical analysis of high-resolution atomic force microscopy (AFM) images. Lambda remains in the random coil conformation, whereas iota and kappa undergo ion-induced coil-helix transitions, with a 2-3-fold increase in chain rigidity. At low ionic strengths, I, the polymer chains sequester Na⁺, leading to a greater flexibility, and beyond a critical I to the formation of an intramolecular single helix. The persistence length exhibits a sublinear dependence on the Debye screening length, κ⁻¹, L(p)(e) ∼ κ(-y) (with 0 < y < 1), deviating from the classical polyelectrolyte behavior expressed by Odijk-Skolnick-Fixman or Barrat-Joanny models. Above a certain I, the L(p) shows an upturn, resulting in polymer stiffening and nonmonotonic behavior. This phenomenon is inferred from specific ion-polymer interactions and/or nonlinear electrostatic physics involving ion-ion correlations.
    [Abstract] [Full Text] [Related] [New Search]