A comparison of liquid nitrogen and liquid helium as cryogens for electron cryotomography
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 ~82K than ~12 K for every dose tested. Thus disappointingly, cooling with liquid helium is actually disadvantageous for cryotomography.
Additional Information
© 2006 Elsevier Inc. Received 29 June 2005; received in revised form 16 November 2005; accepted 7 December 2005. Available online 4 January 2006. We thank Y. He for providing liposomes; T. Wagenknecht and J. Berkowitz for pyruvate dehydrogenase; J. Benjamin, P. Leong, and J. Ding for help with data collection and image processing; and W. Tivol for reading the manuscript. This work was supported in part by NIH Grant PO1 GM66521 to G.J.J., DOE Grant DE-FG02-04ER63785 to G.J.J., a Searle Scholar Award to G.J.J., the Beckman Institute at Caltech, and gifts to Caltech from the Ralph M. Parsons Foundation, the Agouron Institute, and the Gordon and Betty Moore Foundation.Additional details
- Eprint ID
- 24659
- DOI
- 10.1016/j.jsb.2005.12.004
- Resolver ID
- CaltechAUTHORS:20110803-124019191
- PO1 GM66521
- NIH
- DE-FG02-04ER63785
- Department of Energy (DOE)
- Searle Scholars Program
- Caltech Beckman Institute
- Ralph M. Parsons Foundation
- Agouron Institute
- Gordon and Betty Moore Foundation
- Created
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2011-08-03Created from EPrint's datestamp field
- Updated
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2021-11-09Created from EPrint's last_modified field