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Electron Microscopy Sciences

Technical Data Sheets


EMS Catalog #16905

Imidazole is a liquid enhancing buffering agent that, when used with 4% osmium tetroxide solution as a post-fixation for tissue blocks, produces a prominent electron-opaque staining of lipid droplets with no evidence of diffusion.


Tissue is fixed by vascular perfusion with 1.5% glutaraldehyde in 0.1M cacodylate buffer (pH 7.4) containing 4% polyvinyl pyrolidone and 0.05% CaCl2. Sections about 50 um thick are cut and placed in 0.2M Imidazole in which 4% aqueous OsO4 is added.

The final concentration of OsO4 is 2% and the pH is 7.5. Note that the tissue must first be placed in Imidazole buffer; then the OsO4 is added. This post-fixation is carried out for 30 minutes at room temperature.


Angermuller, S., Fahimi, H. Histochem. Journal 14, 823-35 (1982).

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