Search
Close
Search
Advanced Search
Search Menu
AI Discovery Assistant

Abstract

Zero-loss imaging of frozen-hydrated specimens requires a detector with high sensitivity, a low noise level and high spatial resolution, because more electrons are scattered inelastically than elastically by cryo-specimens and the number of electrons detected is ∼1/4 of incident electrons after energy filtering. Cameras using charge-coupled devices (CCDs) are good candidates due to their high sensitivity. They have been used mainly to record electron diffraction patterns for electron crystallography due to their limited spatial resolution but recently used for acquiring direct images due to their convenience. The spatial resolution has been limited by the characteristics of a phosphor that is necessary to convert high-energy electrons to photons and the coupling. We adopted a CsI scintillator with good modulation transfer function (MTF), which was epitaxially grown from each of optical fibres. The stripes of carbon graphite with 3.4 Å spacing and 1.4 Å stripes of gold thin crystals could be recorded with a magnification of 240 000× and 560 000× at 200 kV, respectively. A computed Fourier transform of an image of a frozen-hydrated crystal of catalase containing about 1000 units showed diffraction spots at spatial frequencies of 1/9.6 Å−1 up to 1/8 Å−1 without background subtraction, when the image was recorded at 140 000×. These results show that the resolution of the developed camera was good enough to record images. Our used test method for MTF determination may be useful for others.

CCD camera, epitaxially grown CsI, electron microscopy, catalase, energy-filtered imaging, modulation transfer function
© Oxford University Press 2008
Issue Section:
Biological: Full-length
You do not currently have access to this article.
Download all slides