Abstract
Using methods of IR spectroscopy, light scattering, gel-electrophoresis DNA structural transitions are studied under the action of Cu 2+, Zn 2+, Mn 2+, Ca 2+ and Mg 2+ ions in aqueous solution. Cu 2+, Zn 2+, Mn 2+ and Ca 2+ ions bind both to DNA phosphate groups and bases while Mg 2+ ions—only to phosphate groups of DNA. Upon interaction with divalent metal ions studied (except for Mg 2+ ions) DNA undergoes structural transition into a compact form. DNA compaction is characterized by a drastic decrease in the volume occupied by DNA molecules with reversible formation of DNA dense particles of well-defined finite size and ordered morphology. The DNA secondary structure in condensed particles corresponds to the B-form family. The mechanism of DNA compaction under Mt 2+ ion action is not dominated by electrostatics. The effectiveness of the divalent metal ions studied to induce DNA compaction correlates with the affinity of these ions for DNA nucleic bases: Cu 2+ ≫ Zn 2+ > Mn 2+ > Ca 2+ ≫ Mg 2+. Mt 2+ ion interaction with DNA bases (or Mt 2+ chelation with a base and an oxygen of a phosphate group) may be responsible for DNA compaction. Mt 2+ ion interaction with DNA bases can destabilize DNA causing bends and reducing its persistent length that will facilitate DNA compaction.
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