Buffered Potassium Permanganate-Uranyl Acetate-Lead Citrate Staining Sequence for Ultrathin Sections

Abstract

An effective electron stain for thin sections of tissue cut from most epoxy embedments results from treatment of sections mounted on copper grids with a 0.9% KMnO₄ solution buffered at pH 6.5 with phosphates, then by treatment with a solution of uranyl acetate saturated in 50% ethanol, followed by treatment in a 0.2% lead citrate solution. The use of acid-washed copper grids and a phosphate buffer rinse following permanganate staining minimizes contamination. It is suggested that the increase in electron density produced by the triple stain may result in part from KMnO₄ induced alterations of protein that lead to the formation of an increased number of available bonding sites for the uranyl acetate and lead citrate.