Unravelling the hydrogen bonding patterns in telomeric G-quadruplexes: from structure to function*

In this work, we investigate the molecular basis of the telomere model of ageing. Its key trait is the hydrogen (H–) bonding patterns of G-tetrads that serve a top of G-quadruplexes composing telomeres. We show that these patterns demonstrate a variety of bonding characters – from classic hydrogen bonds to so-called 'over-coordinated oxygen (OCO)' bifurcated H-bonds that thus result in non-rigidity of G-tetrad structures. This work has implications for the functionality of G-quadruplexes and, in turn, for the quadruplex-based telomere model of ageing.