Thermal denaturation profile: A straightforward signature to characterize parallel G-quadruplexes

G-quadruplexes (G4s) are fascinating non-canonical nucleic acid structures that attract broad attention due to their vital roles in gene expression and various applications. G4s exhibit high structural polymorphism and high resolution techniques (NMR, Crystallography) are often required to unambiguously determine G4 topology. Fast and handy techniques such as UV and CD provide interesting structural information. Here, we monitored the thermal denaturation profiles (TDPs) of various G4s at different wavelengths by UV, and confirmed that all G4 topologies (parallel, antiparallel and hybrid) exhibited hyperchromism at 243 nm and hypochromism at 295 nm. Furthermore, the absorption at 260 nm and 275 nm showed a remarkable topology-dependent behavior, and the hypochromism at 275 nm allows to discriminate parallel conformations from other G4 topologies. Therefore, this work provides a new inexpensive identification method for parallel G4 structures as well as a new perspective for the relationship between TDPs and G4 structures.