New measures of anisotropy of cryo-EM maps

This paper proposes two new anisotropy metrics-the Fourier shell occupancy and the Bingham test-that can be used to understand the quality of cryogenic electron microscopy maps. We propose two new measures of resolution anisotropy for cryogenic electron microscopy maps: Fourier shell occupancy (FSO), and the Bingham test (BT). FSO varies from 1 to 0, with 1 representing perfect isotropy, and lower values indicating increasing anisotropy. The threshold FSO = 0.5 occurs at Fourier shell correlation resolution. BT is a hypothesis test that complements the FSO to ensure the existence of anisotropy. FSO and BT allow visualization of resolution anisotropy. We illustrate their use with different experimental cryogenic electron microscopy maps.

Automated summary

This paper introduces two new anisotropy metrics, Fourier shell occupancy (FSO) and the Bingham test (BT), for assessing the quality of cryogenic electron microscopy maps. FSO ranges from 1 to 0, with lower values indicating increasing anisotropy. The threshold FSO = 0.5 corresponds to Fourier shell correlation resolution. BT complements FSO to confirm the presence of anisotropy. FSO and BT enable visualization of resolution anisotropy and are demonstrated using different experimental cryogenic electron microscopy maps.