Isolation of polyadenylic acid-containing RNA using Ca(II)

Purine ribonucleotide homopolymers are insoluble in dilute Ca(II)- or Mg(II)-containing solutions whereas nucleic acid heteropolymers are soluble. The differences in solubility serve as a basis of a new method for separating polyadenylic acid-containing RNA from other nucleic acids. In the presence of as little as 10 mM Ca(II) polyadenylic acid-containing RNA of nucleic acid mixtures selectively coprecipitates with a small amount of added synthetic polyadenylic acid.