Electrostatic polyelectrolyte-myoglobin complexes: relaxation dynamics and viscosity under hydrated and aqueous conditions

Journal article, 2026

This study investigates the structural characteristics of polyelectrolyte-protein electrostatic complexes and their impact on molecular relaxation dynamics and viscosity. A synthetic polyelectrolyte, based on a statistical copolymer comprising positively charged poly(vinyl benzyl trimethylammonium chloride) (PVBTMAC) and poly[oligo(ethylene glycol) methacrylate] (POEGMA), was combined with the globular protein myoglobin. By employing atomic force microscopy (AFM) and X-ray scattering techniques, we report the formation of nanoscale electrostatic core-shell assemblies with characteristic sizes of approximately 50 nm and an average interparticle distance of about 60 nm, along with the presence of larger aggregates in the range of 200-250 nm. This complex formation causes the glass transition related dynamics of the copolymer to slow down, due to strong electrostatic interactions between the charged copolymer segments and the globular protein molecules. These strong ionic interactions distinctly increase the glass transition temperature (Tg) of the copolymer by about 15 K. By rheological and ball viscometry measurements, we observe an increase in macroscopic viscosity, consistent with the formation of electrostatic complexes and their subsequent aggregation. Overall, these findings provide insight into the interactions between a charged synthetic copolymer and a globular protein, contributing to a deeper understanding of the structure-dynamics-property relationships governing polyelectrolyte-protein electrostatic complexes.