Behind the "light-up" fluorescence behavior: why thioflavin-T outperforms benzimidazole derivatives as a fluorescent probe?
JOURNAL OF MOLECULAR STRUCTURE, cilt.1381, 2027 (SCI-Expanded, Scopus)
- Yayın Türü: Makale / Tam Makale
- Cilt numarası: 1381
- Basım Tarihi: 2027
- Doi Numarası: 10.1016/j.molstruc.2026.147764
- Dergi Adı: JOURNAL OF MOLECULAR STRUCTURE
- Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Chemical Abstracts Core, Chimica, Compendex, INSPEC, Academic Search Ultimate (EBSCO), Engineering Source (EBSCO)
- Orta Doğu Teknik Üniversitesi Adresli: Evet
Özet
Thioflavin-T (ThT) is one of the most widely used fluorogenic molecular rotors for the detection of G-quadruplexes (G4) and amyloid fibrils owing to its characteristic restriction of intramolecular rotation upon target binding. Inspired by the structural features of ThT, a series of N-propargyl-substituted benzimidazole derivatives were designed and synthesized to investigate the structural and photophysical requirements governing fluorescence activation and G4 recognition. The synthesized compounds were characterized, and their solventdependent optical properties were compared with those of ThT using UV-Vis absorption and fluorescence spectroscopy. While all compounds exhibited moderate solvent-dependent hypsochromic shifts in their absorption spectra, derivative 5b displayed a distinct photophysical response characterized by pronounced fluorescence enhancement and a bathochromic emission shift in DMSO, which is potentially attributed to its stronger electron-donating substituent and enhanced intramolecular charge-transfer character. Despite these favorable photophysical features, none of the synthesized derivatives demonstrated selective binding toward the G4forming sequence selected from the PIM1 gene. To rationalize these observations, computational studies were performed on both ThT and the benzimidazole derivatives. Despite being structurally analogous to ThT, computational results revealed that upon excitation, the dyes prefer conformational planarization and show fluorescence rather than adopting a perpendicular conformation and relaxing via the twisted intramolecular charge transfer (TICT) decay pathway. Contour map analyses demonstrate that the balance between excited-state planarity, charge-transfer stabilization, and rotational barriers in ThT suppress non-radiative decay upon target binding, explaining its superior fluorogenic performance. These findings provide a framework for understanding the unique photophysical behavior of ThT and establish molecular design principles for the next-generation fluorogenic probes targeting G-quadruplex DNA.