Isolation of the complementary strands of vaccinia virus DNA

Separation of the complementary strands of vaccinia virus DNA by density centrifugation was attempted. Only non-cross-linked DNA molecules were used in these experiments. The best results were obtained using centrifugation in alkaline Cs2SO4 density gradients after denaturation of the DNA, followed by recycling of the isolated strands. Under these conditions, the heavy strand banded at a density of 1.480 g/cm3 and the light strand at 1.465 g/cm3. Incubation of denatured vaccinia virus DNA with ribopolymers, followed by centrifugation in CsCl density gradients, did not result in strand separation. Annealing experiments indicated that the strands isolated by alkaline Cs2SO4 density gradients were complementary.