Effective potential between negatively charged patches on acidic proteins immersed in various electrolyte solutions

Abstract

Effective interactions between O-sized anions in various electrolyte solutions were calculated by using the integral equation theory with some simple models. The results indicated that only multivalent cations mediated a strong effective attraction between O-sized anions at a certain concentration. The effective interaction turned from repulsive to attractive as the electrolyte concentration increased, and the effective attraction decreased when more electrolyte was added. Moreover, the effective interactions between O-sized anions in the electrolyte solution did not present a long repulsive tail, although the effective attraction caused by the divalent cations appeared. By contrast, the effective attraction mediated by monovalent cations and the reentrant behavior did not appear and the effective interaction was basically repulsive. These behaviors agree with the experimental results for reentrant condensation of acidic proteins in various electrolyte solutions. The calculated results suggest that the dissociated carboxylic acidic groups on the proteins form attractive patches between proteins under certain concentration conditions.

Integral equation study of effective attraction between like-charged particles mediated by cations: Comparison between IPY2 and HNC closures

“…Because the calculation cost for "Model A", that was mentioned above, was too expensive, the solvent hard spheres and the macroanions were removed from it. The results calculated using the HNC closure showed that the solvent hard spheres intensify the effective attraction between like-charged particles [40,41]. However, the explicit solvent model was not required, and the implicit solvent model also showed the effective attraction and the reentrant behavior in our studies [40,41].…”

“…The results calculated using the HNC closure showed that the solvent hard spheres intensify the effective attraction between like-charged particles [40,41]. However, the explicit solvent model was not required, and the implicit solvent model also showed the effective attraction and the reentrant behavior in our studies [40,41]. Therefore, this model was selected to reduce the computational costs.…”

“…Therefore, we decided to use g(r). We constructed this model referring to the previous study [40]. In this model, σ AA is 3.62 Å and σ CC is 1.70 Å.…”

“…These values correspond to Cl − and Mg 2+ , whereas Q C is 2.4 e. Table 1 shows the parameters. When these parameters are adopted, the radial distribution function between anions can be expected to show the reentrant behavior [40].…”

Biophysics at Kyushu University

“…His group mainly investigates effective intermolecular interactions in the liquid phase, phase behavior, and diffusion phenomena in a solution using statistical mechanics theory. For example, the group's theoretical studies for effective attraction between like-charged particles in an electrolyte solution explained the reentrant condensation behaviors of acidic protein (Akiyama and Sakata 2011;Suematsu et al 2018). The group is also studying various excluded volume effects in a liquid phase using Asakura-Oosawa theory and integral equation theory for liquids.…”