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J Virol. 1970 May; 5(5): 598-603
Copyright © 1970 American Society for Microbiology. All Rights Reserved.

Centrifugal Sedimentation of Virus Particles for Electron Microscopic Counting

Research Laboratories, The Upjohn Company, Kaiamazoo, Michigan 49001

ABSTRACT

Centrifuge cells with conical chambers were provided by using special inserts for the stainless-steel tubes that fit the Spinco SW-39 rotor. Particulate material, centrifuged in these cells, was collected on carbon-coated glass discs. These discs were exposed to OsO₄ vapor, dehydrated in graded alcohols, air-dried, and metal-shadowed. The metal-shadowed carbon film was floated from the glass, mounted on a grid, and examined. A knowledge of cell geometry and microscope magnification allowed correlation of the number of particles observed to a volume of the original suspension. A precision of ±6% at the 95% confidence level was attained when counting approximately 100 particles per 10,000 x field. Applications and advantages of the method are discussed.