Electron Microscopy of Bacteriophage T7 Internal Head Proteins

1975 ◽  
Vol 33 ◽  
pp. 638-639
Author(s):  
P. Serwer
Keyword(s):  
Electron Microscopy ◽  
Bacteriophage T7 ◽  
Specimen Preparation ◽  
Dna Molecule ◽  
The Core ◽  
Internal Core ◽  
Phage T7 ◽  
T7 Phage ◽  
Preparation Techniques ◽  
Internal Head

The genome of bacteriophage T7 is a duplex DNA molecule packaged in a space whose volume has been measured to be 2.2 x the volume of the B form of T7 DNA. To help determine the mechanism for packaging this DNA, the configuration of proteins inside the phage head has been investigated by electron microscopy. A core which is roughly cylindrical in outline has been observed inside the head of phage T7 using three different specimen preparation techniques.When T7 phage are treated with glutaraldehyde, DNA is ejected from the head often revealing an internal core (dark arrows in Fig. 1). When both the core and tail are present in a particle, the core appears to be coaxial with the tail. Core-tail complexes sometimes dislodge from their normal location and appear attached to the outside of a phage head (light arrow in Fig. 1).

The ionic strength dependence of chromatin folding

1978 ◽  
Vol 36 (2) ◽  
pp. 220-221
Author(s):  
F. Thoma ◽  
TH. Koller
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Ionic Strength ◽  
Specimen Preparation ◽  
Preparation Technique ◽  
Carbon Supports ◽  
Ionic Strength Dependence ◽  
Chromatin Folding ◽  
Strength Dependence ◽  
Preparation Techniques

Under a variety of electron microscope specimen preparation techniques different forms of chromatin appearance can be distinguished: beads-on-a-string, a 100 Å nucleofilament, a 250 Å fiber and a compact 300 to 500 Å fiber.Using a standardized specimen preparation technique we wanted to find out whether there is any relation between these different forms of chromatin or not. We show that with increasing ionic strength a chromatin fiber consisting of a row of nucleo- somes progressively folds up into a solenoid-like structure with a diameter of about 300 Å.For the preparation of chromatin for electron microscopy the avoidance of stretching artifacts during adsorption to the carbon supports is of utmost importance. The samples are fixed with 0.1% glutaraldehyde at 4°C for at least 12 hrs. The material was usually examined between 24 and 48 hrs after the onset of fixation.

Unconventional Specimen Preparation Techniques Using High Resolution Low Voltage Field Emission Scanning Electron Microscopy to Study Cell Motility, Host Cell Invasion, and Internal Cell Structures in Toxoplasma gondii

2002 ◽  
Vol 8 (2) ◽  
pp. 94-103 ◽  
Author(s):  
Heide Schatten ◽  
Hans Ris
Keyword(s):  
Electron Microscopy ◽  
Cell Division ◽  
Host Cell ◽  
Cell Invasion ◽  
Low Voltage ◽  
Cytoskeletal Proteins ◽  
Specimen Preparation ◽  
Host Cell Invasion ◽  
Apicomplexan Parasites ◽  
Preparation Techniques

Apicomplexan parasites employ complex and unconventional mechanisms for cell locomotion, host cell invasion, and cell division that are only poorly understood. While immunofluorescence and conventional transmission electron microscopy have been used to answer questions about the localization of some cytoskeletal proteins and cell organelles, many questions remain unanswered, partly because new methods are needed to study the complex interactions of cytoskeletal proteins and organelles that play a role in cell locomotion, host cell invasion, and cell division. The choice of fixation and preparation methods has proven critical for the analysis of cytoskeletal proteins because of the rapid turnover of actin filaments and the dense spatial organization of the cytoskeleton and its association with the complex membrane system. Here we introduce new methods to study structural aspects of cytoskeletal motility, host cell invasion, and cell division of Toxoplasma gondii, a most suitable laboratory model that is representative of apicomplexan parasites. The novel approach in our experiments is the use of high resolution low voltage field emission scanning electron microscopy (LVFESEM) combined with two new specimen preparation techniques. The first method uses LVFESEM after membrane extraction and stabilization of the cytoskeleton. This method allows viewing of actin filaments which had not been possible with any other method available so far. The second approach of imaging the parasite's ultrastructure and interactions with host cells uses semithick sections (200 nm) that are resin de-embedded (Ris and Malecki, 1993) and imaged with LVFESEM. This method allows analysis of structural detail in the parasite before and after host cell invasion and interactions with the membrane of the parasitophorous vacuole as well as parasite cell division.

A comparative study of the structure of cell wall surfaces: air spaces in leaves are exceptional in having exposed microfibrils

1983 ◽  
Vol 61 (8) ◽  
pp. 2153-2158 ◽  
Author(s):  
J. H. M. Willison ◽  
R. S. Pearce
Keyword(s):  
Electron Microscopy ◽  
Cell Wall ◽  
Gas Exchange ◽  
Intercellular Space ◽  
Specimen Preparation ◽  
Air Space ◽  
Freeze Etching ◽  
Gas Space ◽  
Preparation Techniques ◽  
Space Cell

The study compares the appearance of cell wall outer surfaces adjacent to air spaces in cereal leaves (wheat and rye) with other cell wall surfaces (root hair, water-filled root intercellular space, root gas space) using replica specimen-preparation techniques for electron microscopy, particularly freeze-etching. While all other cell wall outer surfaces are heavily impregnated with materials which fill intermicrofibrillar interstices, those associated with cereal leaf air spaces are impregnated to a lesser extent and are described here as "open." This openness appears to continue at least into the centre (in the radial sense) of the cell wall. There was some evidence for puddling of water at certain sites. The results are discussed in terms of their significance for understanding the nature of leaf air-space cell wall surfaces (it is argued that there is no "cuticle" equivalent to that covering the leaf outer surface), and by consequence the discussion extends to the roles of these surfaces in transpiration and gas exchange.

scholarly journals A Versatile and Affordable Plunge Freezing Instrument for Preparing Frozen Hydrated Specimens for Cryo Transmission Electron Microscopy (CryoEM)

2009 ◽  
Vol 17 (2) ◽  
pp. 14-17 ◽  
Author(s):  
Linda Melanson
Keyword(s):  
Electron Microscopy ◽  
High Vacuum ◽  
Specimen Preparation ◽  
Macromolecular Assemblies ◽  
Preservation Method ◽  
Transmission Electron ◽  
Structural Details ◽  
Soft Polymer ◽  
2D Crystals ◽  
Preparation Techniques

CryoEM is a powerful tool in the arsenal of structural biologists and soft polymer chemists. Hydrated specimens require a preservation method that will counteract the effects of the electron beam and the high vacuum environment of the electron microscope. Classical specimen preparation techniques using chemical fixatives are not able to capture the native structure of the once hydrated specimen perfectly. In contrast to classical methods for preserving specimens for electron microscopy, rapid freezing of radiation-sensitive specimens such as dispersed biological macromolecular assemblies, 2D crystals, and colloids allows the structural details of the specimen to be captured in their essentially native state to near atomic resolution.

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