Abstract
The polycation DEAE-dextran enhances the infectivity of animal virus RNA and DNA for cell cultures by up to 105 times (evidence reviewed by Pagano, 1970). It is thought to form ionic bonds with the phosphate groups of the nucleic acid which not only stabilizes it and partially protects it from nucleases, but also affects the assay cells and facilitates infection.
The apparent infectivities of plant virus nucleic acids have been increased by reconstitution with protein (Fraenkel-Conrat & Singer, 1959), by adding phosphate (Lippincott, 1961), bentonite (Fraenkel-Conrat, Singer & Tsugita, 1961; Singer & Fraenkel-Conrat, 1961), sucrose (Kongsvik & Santilli, 1970) or alkaline buffers (Sarkar, 1963), or by keeping the test plants at 37° or in darkness before inoculation (Bawden & Pirie, 1959; Kongsvik & Santilli, 1970).