Comparative properties of purified preparations of two distinctive strains of tobacco mosaic virus obtained from diseased Turkish tobacco and phlox plants.

Since the isolation of tobacco mosaic virus in the form of a characteristic, crystalline material of high molecular weight (1, 2), a wealth of experimental data has been accumulated (3-7) which indicates that tobacco mosaic virus is, in fact, a nucleoprotein, the molecules or particles of which are 15 by 280 rnp in size, with an anhydrous weight approximately 40 million times that of the hydrogen atom. Purified preparations of the virus were found to possess characteristic biophy&cal, biochemical, and immunochemical properties. However, strains of tobacco mosaic virus were found to yield purified preparations possessing slightly different, yet characteristic, biophysical, biochemical, and immunochemical properties (8-13). Thus, purified preparations of the Holmes’ rib-grass strain of tobacco mosaic virus were found to contain 6.4, 3.5, and 4.3 per cent, respectively, of tyrosine, tryptophane, and phenylalanine, whereas the ordaary strain of tobacco mosaic virus contains 3.8, 4.5, and 6.0 per cent, respectively, of these amino acids. Tobacco mosaic virus contains no histidine, whereas the rib-grass strain contains 0.55 per cent of histidine. The isolation by Loring and Stanley (14) from diseased tomato plants of a purified preparation of tobacco mosaic virus which possessed properties essentially identical with those of virus isolated from diseased Turkish tobacco plants seemed to indicate that the virus leads an autonomous existence that is unaffect.ed, at least to a large degree, by the nature of its host. However, Knight (15, 16) recently studied the properties of purified preparations of influenza virus obtained from infectious allantoic fluid of chick embryos and from infected mouse lungs, and found that, although the biophysical and biochemical properties were essentially the same, the immunochemical properties were different. Purified influenza virus preparations from the two sources were found to possess, in common, an antigenic structure characteristic of the virus, but purified preparations obtained from infectious allantoic fluid were found to possess, in addition, an antigenic structure characteristic of normal allantoic fluid, and purified