Understanding the behavior of macroion in aqueous solution at a fundamental level has huge implications in various fields including biochemistry and material science. In dilute solution, certain macroions can self-assemble into hollow, spherical, single-layered, viral capsid-like, “blackberry”-type structures, which cannot be described by either Debye−Hückel theory for small ions or DLVO theory for colloids. The major driving force of this phenomenon has been found to be counterion-mediated attraction. Therefore, their solution behavior can be greatly affected by extra small counterions. Co-ions were believed to play less important role than counterions in controlling the self-assembly behavior of macroions. However, in this work, we have combined experiment and simulation to show that co-ions can actually have an unprecedented effect--bulky co-ions (Keggin-type polyoxometalates or boron clusters) can slow down or even fully inhibit the self-assembly of macroions ({Mo72Fe30} or {SrPd12}) in dilute solution and significantly decrease the sizes of blackberry structures. Co-ions do co-assemble with macroions and insert into the assembles. This new finding may provide a new sight on mechanism of polyoxometalate anti-virus ability, and various fields including colloids, biology and material science as well.

Unprecedented volume exclusion co-ion effect in self-assembly of macroions

2019 Spring National Meeting

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