Post-acquisition super resolution for cryo-electron microscopy.

Recently, reports have demonstrated achieving resolutions beyond the physical Nyquist limit using super resolution acquisition. Here, we demonstrate exceeding this limitation by pre-processing the raw micrograph movies from counting mode data that have already reached the physical Nyquist reconstruction resolution. To demonstrate functionality, micrograph movies of multiple datasets were pre-processed, showing that it is possible to exceed the physical Nyquist limit via pixel doubling before motion correction. We call this `post-acquisition super resolution', or PASR. While this was originally developed for processing of giant virus datasets, where acquiring at high magnification is not always possible or desirable, it is also shown to work for smaller objects such as adeno-associated virus and apoferritin, both of which are high symmetry, and jack bean urease, with lower symmetry. PASR reduces the magnification required to achieve desired resolutions, which may increase collection efficiency. Further, PASR may be applied on top of acquisition-time super resolution data collection, allowing results to exceed not just the physical sampling limit, but also the super resolution sampling limit. However, to benefit from PASR, data must already reach the Nyquist limit.