Structure and dynamics of hyaluronic acid semidilute solutions: a dielectric spectroscopy study

TL;DR

This study uses dielectric spectroscopy to analyze the structure and electrostatic properties of hyaluronic acid solutions, revealing distinct length scales and electrostatic behaviors compared to DNA, influenced by HA's flexibility and weaker electrostatic interactions.

Contribution

It provides new insights into the electrostatic screening and relaxation dynamics of hyaluronic acid in semidilute solutions, highlighting differences from DNA.

Findings

Relaxation mode in MHz scales with concentration as c^{-0.5}

Relaxation mode in kHz also scales as c^{-0.5}, indicating a different length scale from DNA

Electrostatic persistence length scales with Debye length, not Odijk-Skolnick-Fixman length

Abstract

Dielectric spectroscopy is used to investigate fundamental length scales describing the structure of hyaluronic acid sodium salt (Na-HA) semidilute aqueous solutions. In salt-free regime, the length scale of the relaxation mode detected in MHz range scales with HA concentration as $c_\mathrm{HA}^{-0.5}$ and corresponds to the de Gennes-Pfeuty-Dobrynin correlation length of polyelectrolytes in semidilute solution. The same scaling was observed for the case of long, genomic DNA. Conversely, the length scale of the mode detected in kHz range also varies with HA concentration as $c_\mathrm{HA}^{-0.5}$ which differs from the case of DNA ($c_\mathrm{DNA}^{-0.25}$). The observed behavior suggests that the relaxation in the kHz range reveals the de Gennes-Dobrynin renormalized Debye screening length, and not the average size of the chain, as the pertinent length scale. Similarly, with increasing added salt the electrostatic contribution to the HA persistence length is observed to scale as the Debye length, contrary to scaling pertinent to the Odijk-Skolnick-Fixman electrostatic persistence length observed in the case of DNA. We argue that the observed features of the kHz range relaxation are due to much weaker electrostatic interactions that lead to the absence of Manning condensation as well as a rather high flexibility of HA as compared to DNA.