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Biomedical subjects

A M Schepman

Publications and source records attributed to A M Schepman.

6 recordsLinked to original sources
PubMed1978

Getting started with a scanning transmission electron microscope coupled to a small computer.

A scanning transmission electron microscope (STEM) equipped with a laser-heated gun was coupled to a small computer. Several alterations to the commercially obtained parts of this system are described. On-line operation procedures were developed aiming to reduce the amount of radiation of the specimen area of interest. The resulting system is capable of recording information at the 1.0 to 1.5 nm resolution level by taking advantage of the efficiency of a STEM in recording the information and in controlling the irradiation conditions. These features are important in the study of biological material.

Computers↗
PubMed1977

An analysis of the contracted sheath structure of bacteriophage Mu.

Polymers of contracted sheath particles of bacteriophage Mu were imaged by the negative-staining technique and the electron images were analyzed by optical and digital methods. By means of the three-dimensional reconstruction technique of DeRosier and Klug [Nature (Lond.) 217, 130--134 (1968)] an averaged density map of the sheath structure at a resolution of about 2.0 nm was derived. The sheath is known to consist of one type of protein with a molecular weight of about 52000 [Admiraal and Mellema, J. Ultrastr. Res. 56, 48--64 (1976)]. The interpretation of the map has given information about packing and shape of the protein subunits. One way to describe the structure is by a set of annular rings with 6-fold symmetry. The height of these rings is about 1.8 nm and successive rings in the structure change by about 33 degrees in azimuth. The protein subunit which occupies more than one ring in the polymer, is elongated. The long axis of the protein subunit is at an angle of about 20 degrees with the plane normal to the polymer axis. These data are discussed in relation to changes in the sheath molecules upon contraction.

Coliphages↗