  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.
