Interaction of oxidized polyamines with DNA. III. Association with nucleosides, mono-and polynucleotides

1. 1. Oxidized spermine, an iminodialdehyde, obtained by the enzymic oxidation of spermine, forms complexes with deoxynucleotides, deoxynucleosides, purine bases and synthetic polyribonucleotides. 2. 2. The interaction of oxidized spermine with deoxynucleotides and deoxynucleosides has been demonstrated by spectrophotometric studies. The hyperchromic changes obtained are proportional to the amount of oxidized spermine added and are maximal with guanosine and guanosine 5′-phosphate. 3. 3. Electrophoretic studies indicate that guanine, cytosine and adenine, but not uracil, bind oxidized spermine. 4. 4. The transition from the coiled to the helical structure of polyriboadenylic acid is prevented by oxidized spermine. 5. 5. Complexes between polyribouridylic and polyriboadenylic acid are stabilized by oxidized spermine; the strands do not separate under acid conditions. Hydrogen bonding between complementary polyribonucleotide chains is prevented by pre-incubating the double-stranded structure with oxidized spermine. 6. 6. The binding of oxidized spermine to DNA decreases after deaminating the purine and pyrimidine bases. It has been concluded that the amino groups of the bases are responsible for the irreversible binding of oxidized spermine. The bases bind oxidized spermine in the decreasing order of reactivity: guanine, cytosine, adenine, thymine.