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Scanning Transmission Electron Microscopy Facility

Examples of Good STEM Specimens


Freeze-dried earthworm hemoglobin

A freeze-dried preparation of hemoglobin from the common earthworm is shown in this reduced-scale image from STEM-1. Most of the views are end-on, showing in some cases a central cavity and suggesting six-fold symmetry. The straight rods are Tobacco Mosaic Virus (TMV) particles which are used as internal control in most STEM specimens. The full scale of the dark-field micrograph is 0.512 microns.

Freeze-dried earthworm hemoglobin (click for full size)

Earthworm hemoglobin negatively stained

Earthworm hemoglobin molecules dried in uranyl acetate negative stain is shown at a higher magnification. Strikingly more structural detail is now visible. The six-fold symmetry is clearly apparent in the end-views and much more structure can be seen in the side views. The full scale of this micrograph is 0.256 microns.

Earthworm hemoglobin negatively stained (click for full size)

Unstained bacteriophage T4

A freeze-dried preparation of bacteriophage T4 and TMV. The virus consists of a head (normally full of double-stranded DNA), a tail tube, a baseplate at the end of the tail tube and thin tail fibers attached to the base plate. The particle at the lower right has lost its DNA. The mass per unit length of a tail fiber is 866 +/- 76 kDa, indicating it is a trimer. The full scale of the dark-field micrograph is 0.512 microns.

Unstained bacteriophage T4 (click for full size)

Gold labeled GroEL

The banded structure near the center of the field is a side-view of GroEL chaperone. The 1.4nm gold cluster (visible as a black dot at the left end of the complex) is attached to a small protein being folded by the GroEL. In this bright-field micrograph, the gold cluster appears as a very visible dark spot even though the GroEL is embedded in stain. A few gold-labeled protein fragments are also visible. The full scale of the micrograph is 0.128 microns.

Gold labeled GroEL (click for full size)


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Last Modified: May 4, 2009
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