Determination of the Mass of Viruses by Quantitative Electron Microscopy

Abstract

The photometric method of quantitative determination of dry mass by electron microscopy has been applied to the study of various types of viruses: animal, plant, insect, and bacterial. The method is applicable to all viruses having a mass of 1 x 10-18g or greater. The molecular weight of viruses can be calculated from the mass value by multiplying it by Avogadro's number. In comparison to other methods of determining the molecular weight of viruses, sedimentation and diffusion, sedimentation equilibrium, light scattering, and electron microscopy counting, the method of quantitative electron microscopy is competitive. In some ways quantitative electron microscopy is superior to other methods for the determination of molecular weight: There is no limitation to the size of the virus, no experimental time involved and no concentration and purity of virus preparations required, and finally it is independent of the geometry of the virion. In one important aspect it is unique when compared to other methods; namely, it affords one the capacity to analyse individual virus particles.

Multilamellar spherical particles as potential sources of excessive light scattering in human age-related nuclear cataracts

“…The most common method is to deposit the biological material on a carbon film and employ the scanning transmission mode and darkfield imaging, using specialized instruments that give the mass per unit length of filaments and the mass per unit area of particles (Krzyzanek et al, 2009; Muller and Engel, 2001). Some important examples include the mass per unit length of myosin thick filaments (Lamvik, 1978), virus particles (Bahr et al, 1976), fibrinogen (Mosesson et al, 1981), two-dimensional crystals of aquaporin (Walz et al, 1994), amyloid fibrils (Kammerer et al, 2004) and vimentin intermediate filaments (Herrmann et al, 1996). These specimens have the advantage that they can be deposited on a substrate without stain, fixatives or embedding media that are present in thin sections (Muller and Engel, 2001).…”

The major polypeptides of the nuclear pore complex

“…F. Bahr (Department of Cellular Pathology , Armed Forces Institute of Pathology , Washington DC , USA). As standards latex beads of different diameters and a variety of viruses were used ( [37] ; for further technical details see there and [38]). Dry mass values of nuclear pore complexes were determined using identical a reas of interporous regions of the partly distorted envelopes as weil as of regions of the supporting film.…”

Spectroscopic assays for measuring quantities of erythrocyte membrane "halves".

“…Samples in fluorescence cocktails were transferred to 4-ml quartz cuvettes, 1cm pathlength, and spectra scanned from 250 nm to 750 nm using a Cary-14 spectrophotometer (Varian, Palo Alto, Calif.) equipped with scattered transmission accessory. RBC Hb concentration was based on an Hb millimolar extinction coefficient of 125 at 415 nm ; i .e ., e = 125/millimole monomer of mol wt 16,000 (3), and compared to a concentration of 30 :t 10 pg Hb/cell (4,5,30). For routine assay of Hb in SDS-borate, absorbance was measured at 403 run.…”