Anthropic announced Wednesday that its internal biology research team, working alongside Claude, mapped the first three-dimensional structure of a bacterial vault particle, resolving an atomic model from bacterial and bacteriophage genomes and answering a forty-year structural biology mystery by showing that hollow protein barrels exist outside eukaryotes. Researchers identified uncharacterized major vault protein homologs by scanning fifteen billion predicted protein sequences with Claude, and laboratory validation confirmed that a phage-encoded protein designated L05 self-assembles into symmetrical nanoscale capsules inside Escherichia coli cells. First identified in 1986 in eukaryotic liver tissue, vault particles are the largest non-viral protein complexes in living cells, yet four decades of biochemical study failed to determine their physiological purpose or evolutionary origins. Anthropic’s team directed Claude to examine deep metagenomic databases, uncovering homologous open reading frames across diverse bacterial phyla. Single-particle cryogenic electron microscopy confirmed that the bacteriophage L05 vault organizes into an expanded macromolecular barrel of ninety-six identical subunits, differing from the seventy-eight-subunit stoichiometry of classical mammalian vaults, with forty-eight-fold rotational symmetry along its equatorial midline and a twenty-five percent increase in internal lumen capacity.