9CQ0 image
Deposition Date 2024-07-18
Release Date 2025-06-04
Last Version Date 2025-06-04
Entry Detail
PDB ID:
9CQ0
Keywords:
Title:
Event-based electron counting microED structure of thiostrepton from a single crystal
Biological Source:
Source Organism:
Method Details:
Experimental Method:
Resolution:
1.50 Å
R-Value Free:
0.21
R-Value Work:
0.20
R-Value Observed:
0.20
Space Group:
P 43 21 2
Macromolecular Entities
Polymer Type:polypeptide(L)
Molecule:Thiostrepton
Chain IDs:A
Chain Length:19
Number of Molecules:1
Biological Source:Streptomyces azureus
Peptide-like Molecules
PRD_000223
Primary Citation
Fast event-based electron counting for small-molecule structure determination by MicroED.
Acta Crystallogr.,Sect.C 81 116 130 (2025)
PMID: 39982366 DOI: 10.1107/S2053229624012300

Abstact

Electron counting helped realize the resolution revolution in single-particle cryoEM and is now accelerating the determination of MicroED structures. Its advantages are best demonstrated by new direct electron detectors capable of fast (kilohertz) event-based electron counting (EBEC). This strategy minimizes the inaccuracies introduced by coincidence loss (CL) and promises rapid determination of accurate structures. We used the Direct Electron Apollo camera to leverage EBEC technology for MicroED data collection. Given its ability to count single electrons, the Apollo collects high-quality MicroED data from organic small-molecule crystals illuminated with incident electron beam flux densities as low as 0.01-0.045 e-/Å2/s. Under even the lowest flux density (0.01 e-/Å2/s) condition, fast EBEC data produced ab initio structures of a salen ligand (268 Da) and biotin (244 Da). Each structure was determined from a 100° wedge of data collected from a single crystal in as few as 50 s, with a delivered fluence of only ∼0.5 e-/Å2. Fast EBEC data collected with a fluence of 2.25 or 3.33 e-/Å2 also facilitated a 1.5 Å structure of thiostrepton (1665 Da). While refinement of these structures appeared unaffected by CL, a CL adjustment applied to EBEC data further improved the distribution of intensities measured from the salen ligand and biotin crystals. However, CL adjustment only marginally improved the refinement of their corresponding structures, signaling the already high counting accuracy of detectors with counting rates in the kilohertz range. Overall, by delivering low-dose structure-worthy data, fast EBEC collection strategies open new possibilities for high-throughput MicroED.

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