The inhibition, inactivation and precipitation of tobacco mosaic virus nucleic acid by components of leaf extracts

Unless calcium is removed from leaf extracts containing tobacco mosaic virus nucleic acid, infectivity measurements are invalid. In some circumstances, calcium, nicotine and spermine can prevent the movement of nucleic acid into the water phase when extracts are made in the presence of excess phenol. The concentrations needed for this effect are greater than those usually found in leaf extracts, but it is possible that association of the virus with these sub­stances produces local concentrations large enough to influence the infectivity of extracts.