Journal ArticleDOI
High‐voltage electron diffraction from bacteriorhodopsin (purple membrane) is measurably dynamical
Robert M. Glaeser,T. A. Ceska +1 more
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TLDR
Dynamical diffraction within the single molecular layer of these crystals is responsible for the observed Friedel differences and this opens up the possibility that dynamical effects occurring at lower voltages might be used to phase higher-voltage kinematic diffraction intensities.Abstract:
Electron diffraction patterns of 45 A thick two-dimensional crystalline arrays of a cell membrane protein, bacteriorhodopsin, have been recorded at two electron voltages, namely 20 and 120 kV. Significant intensity differences are observed for Friedel mates at 20 kV, but deviations from Friedel symmetry are quite small at 120 kV. It does not seem likely that the measured Friedel differences can be accounted for by complex atomic structure factors, by curvature of the Ewald sphere, or by effects that might occur as a result of inelastic scattering (absorption). It is therefore concluded that dynamical diffraction within the single molecular layer of these crystals is responsible for the observed Friedel differences. The results are useful in estimating the maximum specimen thickness for which the kinematic approximation may be safely used in electron crystallography of biological macromolecules at the usual electron voltage of 100 kV, or even at higher voltages. The results show that the Friedel differences are independent of resolution and this opens up the possibility that dynamical effects occurring at lower voltages might be used to phase higher-voltage kinematic diffraction intensities.read more
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Journal ArticleDOI
The potential and limitations of neutrons, electrons and X-rays for atomic resolution microscopy of unstained biological molecules.
TL;DR: Because of the lack of sufficiently bright neutron sources in the foreseeable future, electron microscopy in practice provides the greatest potential for immediate progress.
Journal ArticleDOI
Electron-crystallographic refinement of the structure of bacteriorhodopsin.
Nikolaus Grigorieff,Nikolaus Grigorieff,T.A. Ceska,T.A. Ceska,Kenneth H. Downing,Kenneth H. Downing,J.M. Baldwin,J.M. Baldwin,Richard Henderson,Richard Henderson +9 more
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Book ChapterDOI
The Electron Microscope as a Structure Projector
TL;DR: Whether three-dimensional reconstruction from electron micrographs is valid in electron microscopy isquire, where intuition might well lead us to suspect that it is not, and the nature of the interactions between the electrons and the specimen and the characteristics of the image-forming process in the electron microscope are examined.
Journal ArticleDOI
Ab initio structure determination from prion nanocrystals at atomic resolution by MicroED
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TL;DR: Four structures of the amyloid core of the Sup35 prion protein are shown that, if the diffraction resolution is high enough, sufficiently accurate phases can be obtained by direct methods with the cryo-EM method microelectron diffraction (MicroED), just as in X-ray diffraction.
References
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