Ben mijn cursus celbiologie aan het nakijken en stuitte even op een vervelend iets waar ik niet aan uitraak.. het gaat over de transmissie elektronen microscoop. Heb even een quote geplaatst vanuit het handboek.
'The TEM can also be used to study the surface of a specimenand generally at a higher resolution than in the SEMin such a way that individual macromolecules can be seen. As in scanning electron microscopy, a thin film of a heavy metal such as platinum is evaporated onto the dried specimen. The metal is sprayed from an oblique angle so as to deposit a coating that is thicker in some places than othersa process known as shadowing because a shadow effect is created that gives the image a three-dimensional appearance.
Some specimens coated in this way are thin enough or small enough for the electron beam to penetrate them directly. This is the case for individual molecules, viruses, and cell wallsall of which can be dried down, before shadowing, onto a flat supporting film made of a material that is relatively transparent to electrons, such as carbon or plastic. For thicker specimens, the organic material of the cell must be dissolved away after shadowing so that only the thin metal replica of the surface of the specimen is left. The replica is reinforced with a film of carbon so it can be placed on a grid and examined in the transmission electron microscope in the ordinary way.'
Ik kan de gekleurde zin moeilijk begrijpen. Ik dacht dat metalen elektronen weerkaatsen? Waarom spreken ze dan over penetratie?
En waarom gebruik ze een koolstoflaagje bovenop een metaallaagje bij het dikke specimen?
Alvast bedankt!
Prettige avond verder,
Liekeu.
