Guanine-Quadruplexes Studied by Fluorescence Techniques

The study of telomeric DNA has acquired importance through the discovery of the relationship between telomerase activity in most cancer cells and telomere folding into tetraplex structure (guanine-quadruplex). G-quadruplexes exhibit four-stranded structure containing one or more nucleic acid strands with a central channel able to accommodate metal cations. Coordination of certain metal cations stabilizes G-quadruplex as do some promising small organic molecules. Among many techniques employed to explore properties of G-quadruplexes, fluorescence spectroscopy has been recognized as a powerful tool due to high sensitivity and multidimensionality. Information about concentration, molecular structure, binding events, and motion can be obtained using fluorescence methods, e.g., the fluorescence resonance energy transfer (FRET) technique. This review will show how fluorescence spectroscopy contributes to G-quadruplex research and will focuse on the FRET application, describing briefly also the underlying principles. Review will summarize the current developments in the field of the various applications of fluorescent measurements for both the fundamental structural investigations of Gquadruplexes and their complexes with organic ligands as well as some practical applications. Applications include fluorescence and FRET-based selection of efficient quadruplex-binding ligands and metal cations, design of molecular probes for protein recognition and development of sensors for detection of potassium ions in aqueous solution.