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The reproducible observation of unstained embedded cellular material in thin sections: visualisation of an integral membrane protein by a new mode of imaging for STEM.
Author(s) -
Carlemalm E.,
Kellenberger E.
Publication year - 1982
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1002/j.1460-2075.1982.tb01125.x
Subject(s) - micrograph , uranyl acetate , scanning transmission electron microscopy , electron micrographs , electron microscope , transmission electron microscopy , contrast (vision) , biophysics , biology , scanning electron microscope , optics , materials science , physics
The contrast on micrographs obtained by conventional imaging in the conventional transmission electron microscope and in the scanning transmission electron microscope (STEM) (brightfield and darkfield) reflects mainly the variations of the mass‐density and of the thickness of the specimen. The density differences in resin‐embedded, unstained materials are too small to give enough contrast when compared to that produced by the surface perturbations introduced by sectioning. By darkfield imaging, therefore, this variable surface relief does not lead reproducibly to interpretable micrographs of high quality. Imaging by the ratio of elastically over inelastically scattered electrons in the STEM (Z‐contrast) depends primarily on the atomic composition of the material. We present here the first experimental tests of theoretical predictions with thin sections; Z‐contrast micrographs of septate junctions reveal the transmembrane proteins which are not visible in uranyl acetate stained sections viewed by conventional brightfield imaging.