Effects of Polyelectrolyte Chain Stiffness, Charge Mobility, and Charge Sequences on Binding to Proteins and Micelles

Abstract

The binding affinities of polyanions for bovine serum albumin in NaCl solutions from I ) 0.01-0.6 M, were evaluated on the basis of the pH at the point of incipient binding, converting each such pH c value into a critical protein charge Z c . Analogous values of critical charge for mixed micelles were obtained as the cationic surfactant mole fraction Y c . The data were well fitted as Y c or Z c ) KI a , and values of K and a were considered as a function of normalized polymer charge densities (τ), charge mobility, and chain stiffness. Binding increased with chain flexibility and charge mobility, as expected from simulations and theory. Complex effects of τ were related to intrapolyanion repulsions within micelle-bound loops (seen in the simulations) or negative protein domainpolyanion repulsions. The linearity of Z c with I at I < 0.3 M was explained by using protein electrostatic images, showing that Z c at I < 0.3 M depends on a single positive "patch"; the appearance of multiple positive domains I > 0.3 M (lower pH c ) disrupts this simple behavior.

Influence of Explicit Ions on Titration Curves and Conformations of Flexible Polyelectrolytes: A Monte Carlo Study

“…[1][2][3][4][5][6] The range of parameters influencing polyelectrolyte conformation, chemical reactivity, and complexation processes is not completely understood and continues to stimulate intensive research in this field because they control directly many industrial [7][8][9][10] and biological processes. [11][12][13][14] The particular physicochemical properties of polyelectrolyte chains arise from the long-range nature of the Coulomb interactions. In addition, in the vicinity of chains, small charged mobile counterions interact strongly with the chain backbone, leading to a rich conformational behavior by reducing Coulomb repulsions and introducing ion-ion mediated attractions.…”

Interaction of α‐gliadin with polyanions: Design considerations for sequestrants used in supportive treatment of celiac disease

“…29,30 However, the charge heterogeneity of protein introduces repulsive forces between polyanion and protein negative domains. 11 No particles formed for PSS above 10 mg/L ( Figure 5B), indicating that the repulsion as well as repulsion between excess polymer sulfonate groups appears to be sufficient to inhibit a-gliadin aggregation at pH 6.8. The optimal polymer composition for interaction with protein would maximize electrostatic and hydrophobic attraction, but minimize repulsion with protein.…”

“…The optimal polymer composition for interaction with protein would maximize electrostatic and hydrophobic attraction, but minimize repulsion with protein. 11 In copolymers with less SS, the hydrophilic and electrically neutral HEMA segments may sterically hinder the attraction of SS segments with a-gliadin and yet provide stabilization by enrichment on the periphery of complex particles. These factors may explain why PHS1 at 1 mg/L did not, unlike PSS, induce an increase in complex size, but instead suppressed protein aggregation ( Figures 7A and 7B).…”

“…10 Copolymerization of SS with HEMA may be controlled to obtain variations in the resulting polymer charge density, which has been reported recently to affect polymer interaction with proteins. 11,12 Moreover, the inclusion of HEMA units may affect hydrophobic interaction between SS phenyl and protein hydrophobic residues. In this work, interactions between a-gliadin and polymers with different SS and HEMA contents were studied at gastric and intestinal pH using circular dichroism (CD), turbidity, dynamic light scattering (DLS), and zeta potential measurements.…”

Dielectric discontinuity effects on the adsorption of a linear polyelectrolyte at the surface of a neutral nanoparticle

“…4 The complexation of PEs on various substrates has been investigated by a range of experimental methods, theoretical models, and computer simulations. [5][6][7] A series of contributions from Dubin and co-workers 6,[8][9][10][11][12] was made on the adsorption of PEs to spherical nanometric size micelles, dendrimers, and proteins using both experimental and computer simulations. These contributions pointed out the importance of the NP surface charge density and revealed that for PEs of high linear charge density, complexation was electrostatically driven.…”