Spectroscopic analysis reveals the effect of a single nucleotide bulge on G-quadruplex structures.

Here we investigate and reveal the effect of bulge position and bulge identity on G-quadruplexes using label-free spectroscopic techniques. Notably, we report significant differences in the spectroscopic features of bulged DNA and RNA G-quadruplexes, and demonstrate that intrinsic fluorescence can be generally used to detect the formation of canonical and non-canonical G-quadruplexes.