Human telomeric G-quadruplex complexed with the highly selective anticancer drug BRACO-19. A SANS investigation along the melting path.

G-quadruplexes (G4) are the focus of a number of studies in both fundamental and applied research, from cancer biology and novel therapeutics through to nanotechnology. The G4 topology depends on a variety of factors, such as the temperature and the specific interaction with ligands, i.e. potential anti-cancer drugs. Quite recently we have shown that in the case of the human telomeric quadruplex Tel22 both the free system and the one complexed with a model drug undergo melting through a multi-state process. This information is crucial to correctly modelize the Tel22 stability. Here we ask to do a SANS investigation of the complexation of Tel22 with BRACO-19, a potent stabilizer ligand with a remarkable in vivo single-agent antitumor activity. SANS measurements along the thermal unfolding path will reveal the large-scale structural features of the native and intermediate states.