Superconducting lens design

Lefranc, G.; Knapek, E.; Dietrich, I.

doi:10.1016/0304-3991(82)90193-0

Cited by 56 publications

(10 citation statements)

References 8 publications

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“…The first two non-trivial eigenvectors of the data set, which themselves are images (Van Heel, 1984, 1989, will reflect the symmetry properties of the structure as identical symmetric wave patterns which are 900 out of phase (like a sine and a cosine wave). The samples were imaged in the Suleika cryo-electron microscope (Lefranc et al, 1982;Henderson et al, 1990). These techniques are reference-free (Schatz and Van Heel, 1990) and produce unbiased averages of the noisy microscopical images of symmetric structures.…”

Section: Resultsmentioning

confidence: 99%

“…All electron images were recorded using a Suleika 4 K cryo-electron microscope (Lefranc et al, 1982;Henderson et al, 1990) to minimize radiation damage and stain crystallization during the exposure to electrons. All electron images were recorded using a Suleika 4 K cryo-electron microscope (Lefranc et al, 1982;Henderson et al, 1990) to minimize radiation damage and stain crystallization during the exposure to electrons.…”

Section: Methodsmentioning

confidence: 99%

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The portal protein of bacteriophage SPP1: a DNA pump with 13-fold symmetry.

et al. 1993

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Electron microscopy in combination with image processing is a powerful method for obtaining structural information on non‐crystallized biological macromolecules at the 10–50 A resolution level. The processing of noisy microscopical images requires advanced data processing methodologies in which one must carefully avoid the introduction of any form of bias into the data set. Using a novel multivariate statistical approach to the analysis of symmetry, we studied the structure of the bacteriophage SPP1 portal protein oligomer. This portal structure, ubiquitous in icosahedral bacteriophages which package dsDNA, is located at the site of symmetry mismatch between a 5‐fold vertex of the icosahedral shell and the 6‐fold symmetric (helical) tail. From previous studies such ‘head‐to‐tail connector’ structures were generally accepted to be homododecamers assembled in a 12‐fold symmetric ring around a central channel. Using a new analysis methodology we have found that the phage SPP1 portal structure exhibits 13‐fold cyclical symmetry: a new point group organization for oligomeric proteins. A model for the DNA packaging mechanism by 13‐fold symmetric portal protein assemblies is presented which attributes a coherent functional meaning to their unusual symmetry.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

The portal protein of bacteriophage SPP1: a DNA pump with 13-fold symmetry.

et al. 1993

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“…Transmission electron microscopy was performed using a modi®ed Philips model CM20 FEG, within which the commercial objective lens had been replaced by a liquid helium-cooled superconducting objective lens (Zemlin et al, 1996;Lefranc et al, 1982). This electron microscope provides the combined advantages of coherent illumination of the ®eld emission gun and minimal radiation damage due to the $4 K specimen temperature.…”

Section: Electron Microscopymentioning

confidence: 99%

Structure of keyhole limpet hemocyanin type 1 (KLH1) at 15 Å resolution by electron cryomicroscopy and angular reconstitution † 1 †This article is dedicated to the memory of Anneke van Heel. 1Edited by M.F. Moody

Orlova

Dube

Harris

et al. 1997

Journal of Molecular Biology

200

161

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“…7~1 0~~ with C, = 1.35mm and A = 0.037 A. These are the parameters of the microscope used (Lefranc et al, 1982). For demonstration, in Figure 2a, a carbon foil imaged at 45" tilt is shown.…”

Section: The Fading Of the Phase-contrast Transfer Function (Pctf) Dumentioning

confidence: 99%

Dynamic focussing for recording images from tilted samples in small‐spot scanning with a transmission electron microscope

Zemlin

1989

J. Elec. Microsc. Tech.

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For three-dimensional electron microscopical structure research the specimen must be imaged in a tilted position. Specimen tilt is also often needed to achieve an optimal molecular packing orientation. The tilt with respect to the optical axis causes a defocus gradient alongside the imaged area and thus entails the following complications: 1) The phase-contrast transfer function fades for strong defocus; 2) the Fourier coefficients are split; and 3) the signal-to-noise ratio cannot be enhanced by simple averaging. An image procedure with small-spot scanning and simultaneous defocus compensation is proposed which helps to reduce these problems.

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Superconducting lens design

Cited by 56 publications

References 8 publications

The portal protein of bacteriophage SPP1: a DNA pump with 13-fold symmetry.

The portal protein of bacteriophage SPP1: a DNA pump with 13-fold symmetry.

Structure of keyhole limpet hemocyanin type 1 (KLH1) at 15 Å resolution by electron cryomicroscopy and angular reconstitution † 1 †This article is dedicated to the memory of Anneke van Heel. 1Edited by M.F. Moody

Dynamic focussing for recording images from tilted samples in small‐spot scanning with a transmission electron microscope

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