Table 1

Dimensions and mass of pIV. Digital images were recorded from the bright-field detector (for stained samples) or the annular dark-field detector (for unstained samples). The dimensions of both TMV and specimen particles in methylamine vanadate–stained samples (Fig. 2) were measured with the program NIH Image and converted to angstroms with the diameter of TMV (180 Å) as a standard. For mass measurements, unstained samples were used. Areas with clean background and adequate numbers of both TMV and specimen particles (Fig. 1) were selected. The background was computed for clear areas and subtracted from the intensity summed over each particle. The STEM calibration factor was checked in each image against that of TMV; the summed intensities (minus the background) multiplied by this calibration factor give mass values for the specimens. ND, not determined.

Number countedOuter dimension (Å)Inner dimension (Å)Number countedMass (kD)
Double ringNDNDND17* 1230  ± 50
Single ring23140  ± 1080  ± 1044 620  ± 40
Double rectangle1521250  ± 40
Length31210  ± 10
Width33130  ± 1080  ± 10
Single rectangle47610  ± 20
Length1770  ± 10
Width9140  ± 1070  ± 10
  • * Bright images.

  • Less bright images.