Resolving Sub-Microsecond Conformational Dynamics of Vertical Nucleic Acids on Graphene

The function of nucleic acids is governed not only by their structure but also by their dynamics. At the molecular scale, transitions between functional structural states are superimposed on rapid thermal fluctuations, resulting in an intricate interplay that is challenging to resolve experimentally, particularly at the single-molecule level. Here, we introduce a novel approach for unraveling sub-microsecond dynamics in oligonucleotides, enabling direct observation of fluctuations in single DNA molecules. By immobilizing nucleic acids vertically on graphene and exploiting distance-dependent graphene energy transfer of fluorescent molecules attached to the DNA, we relate fluctuations in fluorescence intensity to biomolecular dynamics. We show that ionic strength modulates the fluctuations and that structural defects in DNA, such as nucleotide gaps or mismatches, alter the measured dynamics. The experimental findings are complemented by atomistic molecular dynamics simulations and kinetic Monte Carlo simulations, establishing a direct link between theoretical predictions of structure and dynamics and experimentally accessible fluctuation timescales. Overall, our findings advance the understanding of how thermal fluctuations affect oligonucleotides and are modulated by both external and internal stimuli.