Artificial viruses have potential uses as DNA-based drug delivery particles and structural materials. But scientists find it difficult to make artificial viruses that self-assemble with the same ease as natural viruses. Researchers led by Armando Hernandez-Garcia and Renko de Vries of Wageningen University, in the Netherlands, have made progress toward that goal with a viral coat protein that self-assembles with DNA in a way that mimics the tobacco mosaic virus (Nat. Nanotechnol. 2014, DOI: 10.1038/nnano.2014.169). The protein consists of three distinct blocks: an oligolysine that binds DNA, a silklike sequence that folds into thick filaments, and a hydrophilic random coil that prevents virus particle aggregation. By varying the length of the silklike block from zero to 14 repeat units, the researchers tune the shape of the particles. With shorter silk blocks, the protein simply coats the DNA. With longer silk blocks of 10 or more repeat units, the protein and DNA cooperatively self-assemble to form rod-shaped particles. The researchers show that these viruslike particles can enter cells and protect the DNA from degradation.