A stabilizing and denaturing dual-effect for natural polyamines interacting with G-quadruplexes depending on concentration.

Both G-quadruplexes and natural polyamines are intimately associated with tumor growth and proliferation. The effect of the natural polyamines on telomeric and some oncogenic G-quadruplexes including bcl-2, c-kit, and c-myc G-quadruplexes has been studied by using absorption, fluorescence, CD, and NMR methods. The results exhibited an interesting dual-effect depending on polyamineś concentration. Polyamines promote and stabilize G-quadruplexes under a lower concentration (less than 1mM) but denature G-quadruplexes under a higher concentration (more than 1mM). Probably the electrostatic and hydrophobic effect of polyamines and the hydrogen-bonding interaction between guanines and polyamines were respectively responsible for the stabilizing and denaturing effect.