BPS2026 – Single-molecule force-coupled Raman characterization of DNA-metal complex interactions at single-base resolution

The development of effective anticancer therapies remains a critical challenge, as cancer cells often develop resistance to traditional chemotherapeutics. To overcome resistance and improve selectivity, new metal complexes have been designed to interact with DNA through multiple binding modes and different kinetics. However, the increasing complexity of possible DNA-metal complex interactions makes it challenging to characterize the specific binding modes and associated kinetics for further optimization. Here, we developed a novel integrated technique, single-molecule force-coupled Raman spectroscopy (smFoRS), to elucidate the binding modes and kinetics of metal complexes with DNA with unprecedented single-base resolution. The smFoRS platform integrates optical tweezers-based force spectroscopy with single-molecule surface-enhanced Raman spectroscopy, enabling the direct measurement of binding forces and real-time monitoring of local structural changes at the DNA-binding site. Our results reveal a previously unobserved binding mode in which a metal complex can dynamically transition between minor groove binding and intercalation, depending on the specific DNA sequence and structures. This versatile binding behavior appears to be driven by the steric constraints of the metal complex, which allow it to selectively recognize and engage with DNA mismatches and other structural irregularities. Kinetic analysis further indicates that this transition in binding mode is associated with distinct dissociation rate constants, suggesting opportunities to design metal complexes that differentially target and disrupt specific DNA structural motifs within cancer cells. These findings provide profound mechanistic insights for designing metal-based therapeutics with improved selectivity and efficacy in DNA-targeted cancer treatments.