Experimental methods for studying the interactions between G-quadruplex structures and ligands

The present paper reviews the recent advances in and applications of experimental techniques used to study interactions between G-quadruplex structures and ligands that are potentially of pharmaceutical interest. Several instrumental techniques are used to study such interactions. The application of spectroscopic techniques such as molecular absorption, circular dichroism, molecular fluorescence, mass spectrometry and nuclear magnetic resonance are reviewed and we discuss the type of information (qualitative or quantitative) that can be obtained from the use of each technique. Additionally, the application of complementary techniques such as surface plasmon resonance, isothermal titration calorimetry and different methods based on biochemistry is considered. For each technique, the main applications are presented and they are classified according to the family of the ligand and the type of G-quadruplex forming sequence (human telomeric or promoter region of oncogenes) considered.