Time‐Resolved Multidimensional NMR Spectroscopy Reveals the Bifurcated Folding Pathway of a Thrombin‐Binding DNA G4–Azobenzene Derivative Complex

ABSTRACT Resolving the complex folding landscape of biomolecules contributes greatly to understanding cellular function, since cellular regulation and signal transduction are often linked to their conformational dynamics. We here investigate conformational transitions of a DNA deoxyguanosine G‐quadruplex (G4) induced by binding of a low molecular weight azobenzene derivative. This ligand acts as a photoswitch that triggers conformational rearrangements of the thrombin binding aptamer (TBA) G4 in a reversible manner pending on the photoisomeric state of the ligand (E‐ or Z‐configuration). We exploit the reversible association‐dissociation of the photoactive ligand to extend current real‐time NMR experiments, allowing the in‐depth characterization of the folding pathways for the ligand association and dissociation processes and induction of G4 refolding. The folding pathway features kinetic partitioning and significant population of G4 folding intermediates.