A comparison of liquid nitrogen and liquid helium as cryogens for electron cryotomography

A comparison of liquid nitrogen and liquid helium as cryogens for electron cryotomography The principal resolution limitation in electron cryomicroscopy of frozen-hydrated biological samples is radiation damage. It has long been hoped that cooling such samples to just a few kelvins with liquid helium would slow this damage and allow statistically better-defined images to be recorded. A new “G2 Polara” microscope from FEI Company was used to image various biological samples cooled by either liquid nitrogen or liquid helium to ∼82 or ∼12 K, respectively, and the results were compared with particular interest in the doses (10–200 e − /Å 2 ) and resolutions (3–8 nm) typical for electron cryotomography. Simple dose series revealed a gradual loss of contrast at ∼12 K through the first several tens of e − /Å 2 , after which small bubbles appeared. Single particle reconstructions from each image in a dose series showed no difference in the preservation of medium-resolution (3–5 nm) structural detail at the two temperatures. Tomographic reconstructions produced with total doses between 10 and 350 e − /Å 2 showed better results at ∼82 K than ∼12 K for every dose tested. Thus disappointingly, cooling with liquid helium is actually disadvantageous for cryotomography. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Journal of Structural Biology Elsevier

A comparison of liquid nitrogen and liquid helium as cryogens for electron cryotomography

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Publisher
Elsevier
Copyright
Copyright © 2006 Elsevier Inc.
ISSN
1047-8477
eISSN
1095-8657
DOI
10.1016/j.jsb.2005.12.004
Publisher site
See Article on Publisher Site

Abstract

The principal resolution limitation in electron cryomicroscopy of frozen-hydrated biological samples is radiation damage. It has long been hoped that cooling such samples to just a few kelvins with liquid helium would slow this damage and allow statistically better-defined images to be recorded. A new “G2 Polara” microscope from FEI Company was used to image various biological samples cooled by either liquid nitrogen or liquid helium to ∼82 or ∼12 K, respectively, and the results were compared with particular interest in the doses (10–200 e − /Å 2 ) and resolutions (3–8 nm) typical for electron cryotomography. Simple dose series revealed a gradual loss of contrast at ∼12 K through the first several tens of e − /Å 2 , after which small bubbles appeared. Single particle reconstructions from each image in a dose series showed no difference in the preservation of medium-resolution (3–5 nm) structural detail at the two temperatures. Tomographic reconstructions produced with total doses between 10 and 350 e − /Å 2 showed better results at ∼82 K than ∼12 K for every dose tested. Thus disappointingly, cooling with liquid helium is actually disadvantageous for cryotomography.

Journal

Journal of Structural BiologyElsevier

Published: Mar 1, 2006

References

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