Exceptionally stable, redox-active supramolecular protein assemblies with emergent properties.

The designed assembly of proteins into well-defined supramolecular architectures not only tests our understanding of protein-protein interactions, but it also provides an opportunity to tailor materials with new physical and chemical properties. Previously, we described that RIDC3, a designed variant of the monomeric electron transfer protein cytochrome cb562, could self-assemble through Zn(2+) coordination into uniform 1D nanotubes or 2D arrays with crystalline order. Here we show that these 1D and 2D RIDC3 assemblies display very high chemical stabilities owing to their metal-mediated frameworks, maintaining their structural order in ≥90% (vol/vol) of several polar organic solvents including tetrahydrofuran (THF) and isopropanol (iPrOH). In contrast, the unassembled RIDC3 monomers denature in ∼30% THF and 50% iPrOH, indicating that metal-mediated self-assembly also leads to considerable stabilization of the individual building blocks. The 1D and 2D RIDC3 assemblies are highly thermostable as well, remaining intact at up to ∼70 °C and ∼90 °C, respectively. The 1D nanotubes cleanly convert into the 2D arrays on heating above 70 °C, a rare example of a thermal crystalline-to-crystalline conversion in a biomolecular assembly. Finally, we demonstrate that the Zn-directed RIDC3 assemblies can be used to spatiotemporally control the templated growth of small Pt(0) nanocrystals. This emergent function is enabled by and absolutely dependent on both the supramolecular assembly of RIDC3 molecules (to form a periodically organized structural template) and their innate redox activities (to direct Pt(2+) reduction).

Designed, Helical Protein Nanotubes with Variable Diameters from a Single Building Block.

Due to their structural and mechanical properties, 1D helical protein assemblies represent highly attractive design targets for biomolecular engineering and protein design. Here we present a designed, tetrameric protein building block, Zn8R4, which assembles via Zn coordination interactions into a series of crystalline, helical nanotubes whose widths can be controlled by solution conditions. X-ray crystallography and transmission electron microscopy (TEM) measurements indicate that all classes of protein nanotubes are constructed through the same 2D arrangement of Zn8R4 tetramers held together by Zn coordination. The mechanical properties of these nanotubes are correlated with their widths. All Zn8R4 nanotubes are found to be highly flexible despite possessing crystalline order, owing to their minimal interbuilding-block interactions mediated solely by metal coordination.

Iatrogenic Middle Cerebral Artery Ruptured Pseudoaneurysm Successfully Treated With a Pipeline Embolization Device.

Background: Endovascular advances have shifted the treatment algorithms for traumatic intracranial pseudoaneurysms (IPs) from vessel sacrifice to reconstruction. The Pipeline embolization device (PED) is a flow-diverting stent that promotes endothelialization across the lesion and reconstitutes the parent vessel lumen. Case Report: A 66-year-old male with a history of a right orbital apex lesion presented for biopsy with ophthalmology. Ophthalmology performed a right lateral orbitotomy complicated by brisk arterial bleeding from a proximal right middle cerebral artery (MCA) pseudoaneurysm. The MCA pseudoaneurysm was treated endovascularly with a PED, resulting in immediate stasis of contrast within the lesion without compilation. Interval follow-up angiograms 6 weeks and 6 months after the procedure showed no evidence of recurrence and a widely patent stent. Conclusion: The PED provided a rapid, minimally invasive, and durable treatment option for an acutely ruptured IP. We illustrate that endovascular management with flow diversion can be effectively used in select cases and provides a way to reconstruct the damaged vessel lumen and obliterate the aneurysm.