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Reduction of Charging in Biological Electron Cryomicroscopy

Published online by Cambridge University Press:  02 July 2020

M.B. Sherman ,
J. Brink  and
W. Chiu
M.B. Sherman
Affiliation:
Verna and Marrs McLean Department of Biochemistry, Baylor College of Medicine, One Baylor Plaza, Houston, TX77030, U.S.A.
J. Brink
Affiliation:
Verna and Marrs McLean Department of Biochemistry, Baylor College of Medicine, One Baylor Plaza, Houston, TX77030, U.S.A.
W. Chiu
Affiliation:
Verna and Marrs McLean Department of Biochemistry, Baylor College of Medicine, One Baylor Plaza, Houston, TX77030, U.S.A.
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Extract

High resolution imaging in electron cryomicroscopy of biological macromolecules is strongly affected by beam-induced charging1. Charging is often expressed in frozen or glucose-embedded specimens as an increase in apparent mass-thickness of the irradiated area. Another obvious effect of charging is blurring of both the unscattered beam and reflections in electron diffraction patterns recorded from crystalline specimens. Coating of ice-embedded specimens with a carbon layer helps to improve the stability of the ice and probably reduce charging of the specimen. Coating in a Gatan ion-beam coater (model 681) of glucose-embedded specimens with thin layers of various conductive materials did reduce charging but the specimens were damaged by the high energy ions used for the coating. In general, coating resulted in much weaker reflections in electron diffraction patterns obtained from coated crystals and faster resolution fall-off.

We modified the Gatan coater by outfitting it with a new chamber that replaced the ion-beam deposition capability for thermal evaporation of carbon rods (Fig. 1).

Type
Technologists’ Forum: Special Topics and Symposium
Information
Microscopy and Microanalysis , Volume 3 , Issue S2: Proceedings: Microscopy & Microanalysis '97, Microscopy Society of America 55th Annual Meeting, Microbeam Analysis Society 31st Annual Meeting, Histochemical Society 48th Annual Meeting, Cleveland, Ohio, August 10-14, 1997 , August 1997 , pp. 365 - 366
Copyright
Copyright © Microscopy Society of America 1997

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References

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This research has been supported by NIH grant RR02250.Google Scholar