Forming and removing stain precipitates on ultrathin sections

Area of Science:

• Electron Microscopy
• Materials Science
• Biotechnology

Background:

• Stain precipitates in electron microscopy can obscure ultrastructural details.
• Lead and uranyl salts are commonly used stains, but can form precipitates.
• Precipitates are morphologically diverse, impacting image quality.

Purpose of the Study:

• To classify and characterize stain precipitates in electron microscopy.
• To identify chemical agents capable of removing different precipitate types.
• To assess the efficacy of various treatments on precipitate removal.

Main Methods:

• Ultrathin sections were stained with lead and/or uranyl salts.
• Precipitates were morphologically classified into three types (I, II, III).
• Sections were treated with acetic acid, aqueous uranyl acetate, oxalic acid, and alcoholic uranyl solutions.

Main Results:

• Type I precipitates (lead salts only) were removed by acetic acid or aqueous uranyl acetate.
• Type II precipitates (double staining) were removed by acetic acid, aqueous uranyl acetate, oxalic acid, or alcoholic uranyl solution.
• Type III precipitates (crystalline needles) were unaffected by any tested agents.

Conclusions:

• Specific chemical treatments can effectively remove certain types of electron microscopy stain precipitates.
• Acetic acid and uranyl acetate are effective for type I and II precipitates.
• Type III crystalline needle precipitates present a persistent challenge for removal in electron microscopy.