Interactions of metal ions with polynucleotides and related compounds. III. Degradation of polyribonucleotides by lanthanum ions,

The polyribonucleotides of adenylic, cytidylic, and uridylic acids are degraded in a 2‐hr. period at 64°C. into low molecular weight oligonucleotides and mononucleotides through the action of lanthanum (III) or other trivalent inner transition metal ions. Polyinosinic acid is degraded somewhat more slowly. Cleavage of the polynucleotide chains occurs at the 5′‐phosphate linkages. The 3′‐mononucleotides produced require over 100 hr. of further heating at 64°C. to produce nucleoside and orthophosphate. The reaction between lanthanum (III) and the polynucleoside involves one metal ion for every three nucleotide residues, with each metal ion apparently chelated to a 2′‐hydroxyl and a phosphate group and bound to only one polynucleotide chain.