Suppression of Aggregation in Natural-Semiflexible/Flexible Polyanion Mixtures, and Direct Check of the OSF Model using SANS

TL;DR

This study demonstrates that mixing a semiflexible polyelectrolyte, hyaluronan, with a flexible polyelectrolyte suppresses aggregation, allowing direct observation of single-chain behavior and confirming the Odijk model through SANS measurements.

Contribution

It provides experimental validation of the Odijk model for polyelectrolyte chains and shows how mixture composition can suppress aggregation in biological polyelectrolytes.

Findings

Suppression of HA aggregation in mixtures with flexible polyelectrolytes.

Direct observation of wormlike chain behavior of HA.

Persistence length varies with the square of Debye screening length.

Abstract

Aggregation and other interactions are suppressed for a biological semiflexible polyelectrolyte, hyaluronan (HA), when it is embedded in a mixture with another negatively charged and flexible polyelectrolyte chain, sodium polystyrene sulfonate. We see directly HA only in the mixture using Small-Angle Neutron Scattering, isotopic labelling and contrast matching. At low ionic strength, for which aggregation is usually seen for pure HA solutions, an unambiguous set of experimental results shows that we neither observe HA aggregation nor a polyelectrolyte peak (observed for solutions of single species); instead we observe a wormlike chain behaviour characteristic of single chain with a variation of the persistence length with the square of the Debye screening length, Le~\kappa^-2, as formerly predicted by Odijk and not yet observed on a polymer chain.