Tetraphenylethene derivative that discriminates parallel G-quadruplexes.

G-Quadruplex (G4), as a non-canonical nucleic acid secondary structure, has been proved to be prevalent in genomes and plays important roles in many biological processes. Ligands targeting G4, especially small-molecular fluorescent light-up probes with selectivity for special conformations, are essential for studying the relationship between G4 folding and the cellular response. However, their development still remains challenging but is attracting massive attention. Here, we synthesized a new tetraphenylethene derivative, namely TPE-B, as a parallel G4 probe. Fluorescence experiments showed that TPE-B could give out a strong fluorescence response to the G4 structure. Moreover, it gave a much higher fluorescence intensity response to parallel G4s than anti-parallel ones, which indicated that TPE-B could serve as a special tool for probing parallel G4s. The circular dichroism (CD) spectra and melting curves showed that TPE-B could selectively bind and stabilize parallel G4s without changing their topology. ESI-MS studies showed that TPE-B could bind to parallel G4 with a 1 : 1 stoichiometry. The gel staining results showed that TPE-B was a good candidate for probing parallel G4s. Altogether, the TPE-B molecule may serve as a promising new probe that can discriminate parallel G4s.