A modification of the polyethylene glycol technique for the purification of small quantities of tobacco mosaic virus.

An adaptation of the polyethylene glycol method for the purification of tobacco mosaic virus (sunnhemp strain) from small (2 g) samples of French bean lamina is described. The virus can be precipitated from 1-2 ml of clarified sap by the addition of an equal volume of 8% polyethylene glycol 6000 (w/v) (PEG), and pelleted by centrifugation for 10 min at 1,8000 x g. Details are given of tests which establish that the purity and quality of the virus obtained by the small-scale method are as good as those achieved by the established large-scale method. Even with very low virus titres, the small-scale method effectively precipitates total tobacco mosaic virus nucleoprotein without substantial loss of infectivity. The results are reproducible and in a relatively short time it is possible to purify the virus from large numbers of replicate samples.