Detection of Tetraplex DNA and Detection by Tetraplex DNA.

G-quardruplex (G4) DNA forms through the gathering together of G-quartet planes formed with four guanine (G) bases. G4 DNA stabilizes with potassium ions (K+) by coordination with the G-quartet center. Fluorometric G4 DNA carrying the fluorescence resonance energy transfer (FRET) chromophore pair at both termini has been applied for the fluorometric sensing or imaging of K+ under a homogeneous aqueous medium. This system has realized non-conventional K+ selectivity over the sodium ion (Na+). The selectivity of the fluorescence G4 was converted to Na+ from K+ with a modification of its sequence. On the other hand, G4 DNA detection has been achieved in terms of cancer diagnosis because of a strong relationship of G4 DNA and cancer development. Ligands interacting with G4 are expected to have anti-cancer potential. In addition, fluorometric G4 ligands have been developed and tested as tools for the dynamic monitoring of G4 in living cells. Moreover, fluorometric G4 DNA has been utilized to evaluate the G4 ligand performance.