Inspired by crystals of dimerized proteins, we lithographically design and create monodisperse proteomimetic colloidal particles, or "proteoids", and we show that 2D Brownian systems of certain chiral proteoids self-assemble into dimer microcrystals by slowly crowding the proteoids. Using facially anisotropic roughness controlled depletion attractions, we form enantiopure Brownian monolayers of mobile, hard, microscopic, polymeric proteoids that are dispersed in water and stabilized against aggregation by a short-range screened-charge repulsion. Adding a circular head to one end of an achiral annular sector particle (<i>i.e.</i> C-shape) yields a chiral proteoid; this head sterically blocks one of two pathways for chiral dimerization, leading to enantiopure lock-and-key dimerization as the proteoids become crowded. Corrugations in the exterior surfaces of the chiral dimers that form also lead to ordering of these dimers into crystals in the presence of Brownian fluctuations. Optical microscopy reveals that dimer crystallization is kinetically facilitated and enhanced by tautomerization translocation reactions (TTRs), which effectively enable monomers to move readily in the dense system despite the crowding. These TTRs increase the rate of expulsion of monomer defects from within the crystallites, thereby facilitating crystal growth. Through precise shape-design of sub-particle features, we lithographically mutate the location of the circular head on the proteoid and show that even small changes can affect the crystallization kinetics as well as the primitive vectors of the dimer crystals that result. Thus, we have created a model experimental colloidal system for studying fundamental principles related to dimer crystallization, and we have demonstrated the equivalent of a <i>quinary level</i> of protein assembly by simply crowding certain shape-designed hard proteoids in the presence of entropic Brownian fluctuations.

Dimer crystallization of proteomimetic colloids by shape-designed chiral pathway selection

254th National Meeting (2017)

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