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One was the iron-storing protein apoferritin, which has become a benchmark for cryo-EM resolution records.

In 2020, it crossed the threshold of atomic resolution as researchers using cryo-EM microscopes equipped with improved electron detectors and software mapped the structure of apoferritin, an iron-binding protein.

Researchers in Japan had previously shown they could narrow the resolution to 1.54 angstroms—not quite reaching the point where they could distinguish individual atoms—in a gut protein called apoferritin, which binds and stores iron.

A Cryo-EM map of the protein apoferritin.Credit:

An atomic-resolution map of GABAA, which isn’t as stable as apoferritin, would be a challenge, says Scheres.