Microcrystals in structural biology: small samples, big insights

Abstract

Microcrystals are transforming structural biology by enabling high-resolution structures and time-resolved insights from samples once deemed too small. This commentary highlights recent advances in microfocus X-ray and MicroED methods, emphasizing their growing role as powerful and complementary tools in modern macromolecular crystallography.

Keywords: MicroED; macromolecular crystallography; microcrystals; serial crystallography; structural biology; time-resolved studies.

Figure 1

Microcrystals powering modern structure determination: from X-rays to electrons. Traditional macromolecular crystallography (MX) compared with serial crystallography at X-ray free-electron lasers (XFELs) and synchrotrons, and MicroED using a transmission electron microscope. Traditional MX relies on single, cryo-cooled crystals of ~20–500 µm diameter, typically rotated through ~180° with exposures of 0.1–1°. In contrast, serial crystallography uses thousands of microcrystals (typically 0.2–50 µm), delivered at room temperature in random orientations, with each crystal exposed only once to a focused X-ray pulse. MicroED involves electron diffraction from cryo-cooled nanocrystals (typically 0.05–0.5 µm) mounted on a tilted EM grid, typically collecting ±10° of data per crystal. (Image created with BioRender, https://www.biorender.com.)