||Bacteria Escherichia coli
||Darst, S. A., Kubalek, E. W., & Kornberg, R. D. (1989). Three-dimensional structure of Escherichia coli RNA polymerase holoenzyme determined by electron crystallography. Nature, 340(6236), 730-732 p.730 right column bottom paragraphPubMed ID2671751
|| Darst SA, Ribi HO, Pierce DW, Kornberg RD. Two-dimensional crystals of Escherichia coli RNA polymerase holoenzyme on positively charged lipid layers. J Mol Biol. 1988 Sep 5 203(1):269-73.  Tichelaar W, Schutter WG, Arnberg AC, van Bruggen EF, Stender W. The quaternary structure of Escherichia coli RNA polymerase studied with (scanning) transmission (immuno)electron microscopy. Eur J Biochem. 1983 Sep 15 135(2):263-9.PubMed ID3054121, 6350000
||P.730 right column bottom paragraph: "The map calculated for RNA polymerase in negative stain shows the surface topography of the molecule, so the outermost contour is of interest. This contour was chosen such that the individual molecules in the array were completely disconnected. The overall dimensions of a protein molecule were then ~90×95×160 Å, consistent with the dimensions determined previously by analysis in projection and from views of single particles (primary sources)."