Eukaryotic nuclei contain RNA polymerase I, RNA polymerase II, and RNA polymerase III can be separated by using DEAE-Sephadex ion-exchange chromatography

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#Unit 13. Methods in Biology

For TEM two types of staining is done:

Negative staining

Metal shadowing

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#Unit 13. Methods in Biology

Negative staining- heavy metal coats the grid but is excluded from the regions where the sample has adhered.

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#Unit 13. Methods in Biology

Commonly used heavy metals

Uranyl acetate

Osmium tetraoxide 

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#Unit 13. Methods in Biology

Metal shadowing- thin film of platinum is coated from a fixed angle. it provides information about the three-dimensional topology of the sample.

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#Unit 13. Methods in Biology

Scanning electron microscopy (SEM) allows investigators to view the surfaces of unsectioned metal-coated specimens

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#Unit 13. Methods in Biology

Molecules in the metal coating are excited and release secondary electrons that are focused onto a scintillation detector