An Overview of Microcrystal Electron Diffraction (MicroED)

Abstract

The bedrock of drug discovery and a key tool for understanding cellular function and drug mechanisms of action is the structure determination of chemical compounds, peptides, and proteins. The development of new structure characterization tools, particularly those that fill critical gaps in existing methods, presents important steps forward for structural biology and drug discovery. The emergence of microcrystal electron diffraction (MicroED) expands the application of cryo–electron microscopy to include samples ranging from small molecules and membrane proteins to even large protein complexes using crystals that are one-billionth the size of those required for X-ray crystallography. This review outlines the conception, achievements, and exciting future trajectories for MicroED, an important addition to the existing biophysical toolkit.

Absolute Configuration Determination of Chiral API Molecules by MicroED Analysis of Cocrystal Powders Formed Based on Cocrystal Propensity Prediction Calculations**

“…Unfortunately, scXRD is limited by the need to grow suitably sized crystals (≥5 μm×5 μm×5 μm), which can be challenging for many APIs. Recently, a new method has emerged for determining structures from microcrystalline powders termed microcrystal electron diffraction (MicroED), a 3D electron diffraction (3D ED) method [8–10] . This method has recently been applied to a growing number of API molecules [11,12] .…”

“…Recently, a new method has emerged for determining structures from microcrystalline powders termed microcrystal electron diffraction (MicroED), a 3D electron diffraction (3D ED) method. [8][9][10] This method has recently been applied to a growing number of API molecules. [11,12] Unfortunately, absolute configuration determination by MicroED is not as straightforward as for scXRD.…”

Microcrystal electron diffraction (MicroED) structure determination of a mechanochemically synthesized co-crystal not affordable from solution crystallization

“…[22][23][24][25][26][27] Very thin crystals show clear electron diffraction patterns owing to the strong interaction between electrons and matter, providing crystal structures directly from the powders. 16,17,28 By exploiting this advantage, MicroED was applied to a ground co-crystal, whose structure was reported to be not accessible by the solution method in this study. Figure 1 shows a representative example, focusing on a 2:1 co-crystal of 2-aminopyrimidine (2AP) and succinic acid (SA), which was first synthesized by Etter et al in 1990.…”

“…11 However, this technique is susceptible to diffraction peak overlap due to coexistence of polymorphs and crystal-size-dependent peak broadening which hinders the analysis of the crystal structure. 7,12 Microcrystal electron diffraction (MicroED) [13][14][15][16][17][18] is another technique for determining the structure of nano crystals based on electron microscopy. MicroED was initially developed for protein crystals [19][20][21] but has been used for an increasing variety of small-molecule crystals in recent years.…”

“…Microcrystal electron diffraction (MicroED) 13–18 is another technique for determining the structure of nano crystals based on electron microscopy. MicroED was initially developed for protein crystals 19–21 but has been used for an increasing variety of small-molecule crystals in recent years.…”