Macromolecular Crowding in Solutions of Bovine Serum Albumin and Neutral Polymers

The paper analyzes the dependence of viscosity on concentration of macromolecules (c) for saline solutions containing bovine serum albumin (BSA), in presence of two water soluble polymers: poly(vinyl alcohol) (PVA) and pullulan (PULL). For dilute solutions, the dependence of relative viscosity on concentration allows the determination of intrinsic viscosity, [$\eta$], through a new model developed by Wolf [Macromolecules, 52, 2019, 3231–3236]. PVA/BSA behaves as an ideal system, whereas intermolecular complexes are formed in the solutions of PULL/BSA. For semidilute and concentrated solutions, the macromolecular crowding influences the overall behavior. New phenomena were observed: a phase separation for PVA/protein concentrated solutions or, extended entangled network mediated by cations present in solution in the case of BSA/PULL mixtures. A generalized behavior describing the viscometric behavior for both systems was obtained from the dependence of the specific viscosity as a function of reduced polymer concentration, $c\times[\eta]$.