PMID: 4104Apr 2, 1976

The effect of silver ion binding and pH on the buoyant density of DNA and its use in fractionating heterogeneous DNA

Biochimica Et Biophysica Acta
F P Rinehart, C W Schmid


1. The effect of pH on the buoyant density of the complexes of Ag+ with DNA has been studied using 3H-labeled human DNA and several bacterial DNAs to determine the conditions necessary for the maximum resolution of compositional heterogeneity. In neutral CS2SO4 density gradients, Ag+ complexes with (G - C)-rich components are always denser than those with (A - T)-rich components, since (G - C)rich DNAs have a larger affinity for Ag+ than (A - T)-rich DNAs and their complexes are denser than (A - T)-rich complexes. In alkaline (pH greater than 9) CS2SO4 gradients, the buoyant density of the Ag+ - DNA complex is not a simple function of base composition. The Ag+ affinity of (A - T)-rich DNA is larger than that of (G - C)-rich DNA but the density of a (G - C)-rich complex is larger. Thus the ordering of the buoyant density changes depends on the amount of added Ag+. 2. The problem of resolving the density heterogeneity within a tracer DNA, and minor components of DNA, is explored and useful fractionation techniques are developed.

Related Concepts

Centrifugation, Density Gradient
Clostridium perfringens
DNA, Double-Stranded
DNA, Bacterial
Alkalescens-Dispar Group
Hydrogen-Ion Concentration

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