DNA aggregation induced by Mg2+ ions under different conditions

Cations‐induced DNA aggregation can modify the local structure of oligonucleotides and has potential applications in medicine and biotechnology. Here, we used atomic force microscopy to investigate λ‐DNA aggregation on Mg²⁺‐treated glass (Mg²⁺/glass) and in Mg²⁺ solution. Atomic force microscopy topography images showed that some DNA fragments were slightly stacked together on 10 mM Mg²⁺/glass and stacked stronger on ≥50 mM Mg²⁺/glass. They also showed that DNA aggregated stronger in Mg²⁺ solution than on Mg²⁺/glass, ie, DNAs are strongly stacked and twisted at 10 mM Mg²⁺, rolled together at 50 mM Mg²⁺, and slightly aggregated to form small particles at 100 mM Mg²⁺. At a specific condition, ie, heating λ‐DNA to 92°C, cooling down to 75°C, adding Mg²⁺, and vortexing the resulting solution, DNA strongly aggregated and formed pancake‐like shapes at 10 and 50 mM or a large aggregate at 100 mM Mg²⁺ solutions. Our results may be helpful for medical applications and gene therapy using cation‐DNA technology.