Standards for MicroED

TL;DR

This paper discusses the growing adoption of MicroED and identifies key parameters and challenges for its wider use in structural biology.

Contribution

The paper highlights best practices and data quality parameters specific to MicroED compared to X-ray diffraction.

Findings

MicroED data often has higher resolution than X-ray diffraction due to smaller crystal sizes.

Rmerge and CC1/2 are key parameters distinguishing MicroED from X-ray data quality.

Lack of infrastructure and experience remains a barrier to broader adoption of MicroED.

Abstract

As the electron diffraction technique MicroED gains momentum and is increasingly embraced by researchers in both academia and industry, we have the opportunity to familiarize ourselves with the characteristics of MicroED data and results. The number of refined structures and their associated data is steadily growing and becoming more accessible to the scientific community, offering valuable insights into the significance and quality of MicroED-derived structures. Additionally, the growing body of experience is helping to identify best practices for the technique. Generally, MicroED maps tend to have higher resolution than what was possible with xray diffraction given the small size of the crystals. As a main observation, it is illustrative to note that for structures in Protein Data Bank (PDB) (Berman et al.), the parameters Rmerge and CC1/2 are the only parameters in this analysis where clearer differences between MicroED and X-ray data can be discerned. These parameters are related to the internal consistency of the measured intensities and describe the data before merging of the intensities and multiple data sets. For structures deposited to Cambridge Structural Database (CSD) (Groom et al.), also R1 displays larger differences, but produces reliable models. At this stage the biggest hurdle for an even wider dissemination of the MicroED technology to the scientific community is the lack of experience, infrastructure and national facilities with robust dedicated instruments for the method