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【Abstract】

Although negatively charged particles repel each other in a vacuum, we often observe the effective attraction between negatively charged proteins in an electrolyte. This effective attraction only appears at a certain electrolyte concentration. For example, Zhang et al. have reported the reentrant condensation of negatively charged proteins in an electrolyte solution that contains multivalent cations. The attraction appears only at mM-order electrolyte concentration. DNA compaction also shows similar reentrant behavior. These reentrant behaviors regarding effective interaction completely differ from the usual screened Coulomb interaction explained in textbooks.
Recently, similar reentrant behaviors were discovered in the various experimental results, and the universality is discussed in electrolyte solution systems containing multivalent cations. This effective interaction must be important to understand the construction of nanostructures in biological systems. In the present talk, I will explain the experimental results and discuss our theoretical results.
We have studied this phenomenon using statistical mechanics theory and molecular simulations. Our calculated results also demonstrate the effective attraction and reentrant behaviors when the Coulomb interaction is larger than the thermal energy. Based on our results, we explain the mechanism.