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Applicability of thin film phase plates in biological electron microscopy

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ABSTRACT

Presented is an evaluation of phase contrast techniques in transmission electron microscopy. The traditional defocus phase contrast is compared to two recently developed phase plate techniques. One is the Zernike phase contrast transmission electron microscope, the other is the Hilbert differential contrast thransmission electron microscope. The imaging characteristics of each technique are discussed. Phase plate techniques provide improved contrast for ice-embedded biological samples which are a challenge for the conventional defocus phase contrast. The flat spectral response of the Zernike and Hilbert modes extends towards the low frequencies which are severely suppressed in the conventional defocus mode. Target applications for each of the phase contrast techniques are discussed based on the specifics of image formation and spectral transfer.

No MeSH data available.


(a) Scheme of the conventional TEM and its phase CTFs (b). (c) Scheme of the Zernike phase contrast TEM and its phase CTFs (d). (e) Scheme of the Hilbert differential contrast TEM and its phase CTF (f).
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f1-2_35: (a) Scheme of the conventional TEM and its phase CTFs (b). (c) Scheme of the Zernike phase contrast TEM and its phase CTFs (d). (e) Scheme of the Hilbert differential contrast TEM and its phase CTF (f).

Mentions: In Fig. 1a is shown a scheme of the conventional TEM. It employs a circular aperture at the back focal plane of the objective lens which intercepts electrons scattered outside the radius of the aperture. Two kinds of contrast generation are important in the observation of biological samples by conventional TEM. If the sample is stained by heavy elements some of the incident electrons are scattered at high angles and thus intercepted by the objective aperture. This produces amplitude (or aperture) contrast in the final image. Areas which have more of the staining agent appear darker in the image. Staining however is a double-edged sword. It increases the contrast but also introduces artifacts and limits the resolution because of the non-uniformity and granularity of the stain.


Applicability of thin film phase plates in biological electron microscopy
(a) Scheme of the conventional TEM and its phase CTFs (b). (c) Scheme of the Zernike phase contrast TEM and its phase CTFs (d). (e) Scheme of the Hilbert differential contrast TEM and its phase CTF (f).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC5036645&req=5

f1-2_35: (a) Scheme of the conventional TEM and its phase CTFs (b). (c) Scheme of the Zernike phase contrast TEM and its phase CTFs (d). (e) Scheme of the Hilbert differential contrast TEM and its phase CTF (f).
Mentions: In Fig. 1a is shown a scheme of the conventional TEM. It employs a circular aperture at the back focal plane of the objective lens which intercepts electrons scattered outside the radius of the aperture. Two kinds of contrast generation are important in the observation of biological samples by conventional TEM. If the sample is stained by heavy elements some of the incident electrons are scattered at high angles and thus intercepted by the objective aperture. This produces amplitude (or aperture) contrast in the final image. Areas which have more of the staining agent appear darker in the image. Staining however is a double-edged sword. It increases the contrast but also introduces artifacts and limits the resolution because of the non-uniformity and granularity of the stain.

View Article: PubMed Central - PubMed

ABSTRACT

Presented is an evaluation of phase contrast techniques in transmission electron microscopy. The traditional defocus phase contrast is compared to two recently developed phase plate techniques. One is the Zernike phase contrast transmission electron microscope, the other is the Hilbert differential contrast thransmission electron microscope. The imaging characteristics of each technique are discussed. Phase plate techniques provide improved contrast for ice-embedded biological samples which are a challenge for the conventional defocus phase contrast. The flat spectral response of the Zernike and Hilbert modes extends towards the low frequencies which are severely suppressed in the conventional defocus mode. Target applications for each of the phase contrast techniques are discussed based on the specifics of image formation and spectral transfer.

No MeSH data available.