Electron counting and beam-induced motion correction enable near-atomic-resolution single-particle cryo-EM
Xueming Li,Paul Mooney,Shawn Q. Zheng,Shawn Q. Zheng,Christopher R. Booth,Michael B. Braunfeld,Michael B. Braunfeld,Sander Gubbens,David A. Agard,David A. Agard,Yifan Cheng +10 more
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TLDR
This approach determined a 3.3-Å-resolution structure of an ∼700-kDa protein with D7 symmetry, the Thermoplasma acidophilum 20S proteasome, showing clear side-chain density and greatly enhances image quality and data acquisition efficiency.Abstract:
In recent work with large high-symmetry viruses, single-particle electron cryomicroscopy (cryo-EM) has achieved the determination of near-atomic-resolution structures by allowing direct fitting of atomic models into experimental density maps. However, achieving this goal with smaller particles of lower symmetry remains challenging. Using a newly developed single electron-counting detector, we confirmed that electron beam-induced motion substantially degrades resolution, and we showed that the combination of rapid readout and nearly noiseless electron counting allow image blurring to be corrected to subpixel accuracy, restoring intrinsic image information to high resolution (Thon rings visible to ∼3 A). Using this approach, we determined a 3.3-A-resolution structure of an ∼700-kDa protein with D7 symmetry, the Thermoplasma acidophilum 20S proteasome, showing clear side-chain density. Our method greatly enhances image quality and data acquisition efficiency-key bottlenecks in applying near-atomic-resolution cryo-EM to a broad range of protein samples.read more
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Crystal structure of the 20S proteasome from the archaeon T. acidophilum at 3.4 A resolution.
TL;DR: The three-dimensional structure of the proteasome from the archaebacterium Thermoplasma acidophilum has been elucidated by x-ray crystallographic analysis by means of isomorphous replacement and cyclic averaging.
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Accurate determination of local defocus and specimen tilt in electron microscopy
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Prevention of overfitting in cryo-EM structure determination
Sjors H.W. Scheres,Shaoxia Chen +1 more
TL;DR: Analysis of simulated data with realistic signal-to-noise ratios indicates that the accuracy of the orientation determination is not affected by the exclusion of high-frequency terms, nor by the use of a model that is reconstructed from only half of the particles, as expected.