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Huddy, Hsia, Kibler, Xu & 27 others in the Nobel Prize winning group of David Baker have designed standardized protein building blocks that self assemble into a wide range of nanostructures. The building blocks attach to each other at engineered sites and angles, and come in various sizes.

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F Wang, Y Gu, JP O'Brien, SM Yi, SE Yalcin, V Srikanth, C Shen, D Vu, NL Ing, AI Hochbaum, EH Egelman, NS Malvankar. Cell 2019 doi: 10.1016/j.cell.2019.03.029
Bacteria living in anaerobic environments (no oxygen) need alternative electron acceptors in order to get energy from their food. An acceptor abundant in the earth's crust is red iron oxide ("rust"), which gets reduced to black iron oxide (magnetite). Many bacteria, such as Geobacter, get their metabolic energy by transferring electrons to acceptors that are multiple cell diameters distant, using protein nanowires. These were long thought to be pili. But when the structure of the nanowires was solved in 2019, to everyone's surprise, they turned out to be unprecedented linear polymers of multi-heme cytochromes. The hemes form an electrically conductive chain in the cores of these nanowires.

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Touching stretches cell membranes, opening mechanosensitive ion channels, leading to sensation by the nervous system. Pictured is the transmembrane region of a similar channel in bacteria. When closed, the narrow opening is lined by hydrophobic amino acid sidechains, making it non-conductive to ions.

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