“…The three G4s forming regions were characterized in the past by a panel of spectroscopic techniques, including UV-visible absorption (UV-Vis) ( 25–27 , 30 , 31 ), circular dichroism (CD) ( 25–27 , 30–32 ), nuclear magnetic resonance (NMR) ( 25 , 27 , 28 , 31 , 32 ). In addition, c-kit1 and c-kit2 were probed by single molecule techniques ( 26 , 29 , 33 ), including fluorescence resonance energy transfer (FRET), a widely applied technique to elucidate the conformational features of biomolecules ( 34–37 ). The c-kit* sequence, being the last one to be identified, has been investigated to a lesser extent, and, to the best of our knowledge, there exists only one study in which its folding has been characterized at the single-molecule level, namely by exploiting magnetic tweezers ( 33 ).…”