INTERACTION OF OXIDIZED POLYAMINES WITH DNA .4. EFFECT OF DNA COMPOSITION ON BINDING

1. 1. Oxidized spermine, an iminodialdehyde obtained by the enzymic oxidation of spermine, is bound to DNA by electrostatic and covalent bonds. The covalent binding of oxidized spermine is irreversible and is completed after incubation with DNA for 30 h at 35°. 2. 2. The capacity of DNA to bind oxidized spermine is directly proportional to its guanine-cytosine content. This has been demonstrated by (a) alcohol precipitation of DNA-oxidized spermine complexes, (b) fractionation on hydroxyapatite columns, (c) alkali denaturation of complexes with DNA derived from various sources. 3. 3. Sonicated DNA has been fractionated on hydroxyapatite columns to yield guanine-cytosine-rich polynucleotides. These preparations have a higher capacity to bind oxidized spermine than polynucleotide chains poor in guanine-cytosine pairs. 4. 4. Native bihelical DNA binds 3-15 molecules of oxidized spermine per 103 nucleotide units. Denatured DNA has a higher binding capacity. © 1969.