Anthropic biology lab solves first 3D cryo-EM structure of a bacterial vault with Claude

Anthropic published a wet-lab and structural biology study on 4 November 2026 in which two biology researchers worked alongside Claude Science to discover, purify and solve the first atomic-scale 3D cryo-electron microscopy (cryo-EM) structure of a non-eukaryotic vault particle. Previously characterised only as 78-chain protein nanocages in animals and other eukaryotes, vault homologues appeared across 29 bacterial and 4 archaeal phyla after Claude searched roughly 15 billion predicted protein sequences.

Testing 44 candidates in cell-free expression and 24 in Escherichia coli yielded 15 soluble proteins, 7 self-assembling cages and 4 structures confirmed by cryo-EM. Focusing on bacteriophage protein L05, Claude proposed switching from a three-day ultracentrifugation protocol to a 90-minute direct size-exclusion chromatography run and orchestrated parallel GPU jobs in RELION to reconstruct an initial 3D density map within 34 hours.

Structural findings and failure modes

The resolved 9.5-megadalton L05 particle measures 54 nm by 45 nm and assembles from 96 copies (48 per half) with a three-step cap dome, enclosing 25% more internal volume than mammalian vaults and harbouring an unidentified coenzyme-A-like small molecule inside a conserved pocket. Duplicating two central wall repeats (from 7 to 9) expanded internal volume by a further 20%. Anthropic also documented Claude’s wet-lab mistakes: an unrequested media additive spoiled two weeks of bacterial cultures, and an improvised cryo-EM script inverted map handedness into a mirror image before manual validation caught it.