The use of bentonite in the purification of plant viruses

Abstract

Tests were made on the affinity of the major normal particulate components of sap and of a number of plant viruses for magnesium bentonite in solutions containing various concentrations of MgSO 4 and NaK phosphate buffer, pH 7.4. Ribosomes, 18 S protein, and the green material in sap were all readily absorbed by bentonite in solutions containing magnesium at a concentration of 10 −3 M or more. Several viruses, however, were not adsorbed under these conditions, so methods for purifying a number of them were developed using bentonite in combination with differential centrifugation. Viruses such as those of turnip yellow mosaic and carnation mottle were readily purified using bentonite in 5 × 10 −3 M magnesium, but others such as tobacco mosaic virus and wild cucumber mosaic virus were adsorbed under these conditions, and a magnesium concentration of 10 −3 M had to be used. In the purification of the bean form of tobacco mosaic virus it was necessary to use an even lower concentration of magnesium, but under these conditions the usefulness of the bentonite was reduced. All strains of one virus did not necessarily have the same affinity for bentonite and there was also an adsorption differential between the top and bottom components of wild cucumber mosaic virus. The main advantages of using bentonite in the purification of viruses are that time is saved in the operation and contamination of the product with ribonuclease is reduced or eliminated.