Evaluation of G-quartet-forming deoxyguanines in antiparallel G-quadruplexes using optical spectroscopy and...

Due to the dynamic conformations of G-quadruplex structures (G4), determining the guanines that form G4 in a guanine-rich sequence is elusive. Here, we report a method for identifying deoxyguanines (dGs) forming antiparallel G4 by optical spectroscopy. The method, referred to as dG-to-deoxythymidine (dT) scanning, compares the spectra between a wild type and a single nucleobase dG-to-dT mutant at all dG positions. The most strongly involved dGs to form antiparallel G4 in the two model sequences were estimated using dG-to-dT scanning by circular dichroism (CD) and UV-Vis melting curve. This simple and robust method will facilitate understanding de novo antiparallel G4.