New computational method pushes cryo-EM beyond traditional resolution limits

Cryo-electron microscopy (cryo-EM) has become a powerful tool for determining the structures of proteins, viruses, and molecular complexes at near-atomic resolution. However, the achievable resolution is fundamentally limited by the Nyquist sampling frequency, which is determined by detector pixel size and microscope magnification. Once this physical limit is reached, researchers typically must recollect data at higher magnification, requiring additional microscope time, increased storage capacity, and often fewer particles per image.

Researchers from the Exploratory Research Center on Life and Living Systems and the National Institute for Physiological Sciences have developed a new computational method called Post-Acquisition Super Resolution (PASR), which enables cryo-EM datasets to surpass conventional physical Nyquist limits after data collection. PASR works by computationally subdividing detector pixels before motion correction, allowing subtle particle motion between movie frames to recover higher-frequency structural information.

The method was successfully tested on multiple datasets, including apoferritin, adeno-associated virus, jack bean urease, and the giant virus Melbournevirus, using standard cryo-EM processing software such as RELION and CryoSPARC. PASR improved map quality and enabled higher-resolution reconstructions without visible artifacts. The approach may reduce microscope usage time and data-storage demands while improving analysis of large, flexible, or heterogeneous biological complexes.