Unique Symmetry-Breaking Phenomenon during the Self-assembly of Macroions Elucidated by Simulation

Abstract

Various soluble hydrophilic macroions can self-assemble into hollow, spherical, monolayered supramolecular “blackberry”-type structures, despite their like-charged nature. However, how the 3-D symmetrical macroions prefer to form 2-D monolayers in bulk solution, especially for the highly symmetrical “Keplerate” polyoxometalates and functionalized C60 macroions has been a mystery. Through molecular dynamics simulations, using a model specifically designed for macroions in solution, the mechanism of this intriguing symmetry-breaking process is found to be related to the apparently asymmetric charge distribution on the surface of macroions in the equatorial belt area (the area which can be effectively involved in the counterion-mediated attraction). As a result, the electric field lines around macroions during the self-assembly process clearly show that the symmetry-breaking happens at the dimer level effectively defining the plane of the self-assembly. These findings are expected to contribute to our fundamental knowledge of complex solution systems that are found in many fields from materials science to biological phenomena.

Continuous Curvature Change into Controllable and Responsive Onion-like Vesicles by Rigid Sphere–Rod Amphiphiles

“…Coarse-grained (CG) simulation was further applied to further understand the self-assembly behavior at the molecular level. − In CG simulation, several critical steps during the self-assembly process are observed. Initially, the OF rods strongly interact with each other and attract several hybrids to form the basic building blocks of bilayers (Figure e), which aims to minimize the contact areas between hydrophobic OFs and polar solvents.…”

Co-ion Effects in the Self-Assembly of Macroions: From Co-ions to Co-macroions and to the Unique Feature of Self-Recognition

“…One solution (referred to hereafter as system A) contains 20 large charged spheres representing macroions, and the other solution (system B) contains 20 small charged spheres representing subnanometer co-ions. After running the two systems for at least 500 ns, the macroions self-assembled into a two-dimensional (2D) membrane, as previously reported, whereas the subnanometer co-ion showed no sign of self-assembly in solution and stayed well-dispersed in solution. These simulation results are consistent with the current experimental observations.…”

“…In order to further investigate the unprecedented effect of subnanometer co-ions on macroions self-assembly, molecular dynamics simulation using a versatile coarse-grained (CG) model , was also performed in this work. It is difficult to simulate the formation of a complete, closed blackberry structure, as one blackberry structure contains thousands of macroions .…”

Competition and Cooperation among Different Attractive Forces in Solutions of Inorganic–Organic Hybrids Containing Macroionic Clusters

“…The blue beads represent the macroions, and the small red ones represent their counterions. Adapted with permission from ref . Copyright 2018 Nature Publishing Group.…”

“…70 Coarse-grained simulations have confirmed many of our experimental observations. 71,72 For example, the macroions will tend to attract each other only when carrying a certain number of charges, and the attraction leads to the growth of a 2D, singlelayered sheet (Figure 2b). When the sheet is large enough, its edge energy will surpass the bending energy so that it prefers to bend and close the edge, making a 3D, single-layer, hollow, spherical structure.…”