Single Molecule Observations of DNA Hybridization Kinetics

Two 25 base-pair complementary DNA strands are encapsulated within an optically trapped nano-droplet, and we observe the kinetics of their hybridization in dynamic equilibrium via single molecule fluorescence resonance energy transfer (FRET) as a function of temperature and of the solution's NaCl concentration. We have directly observed binding and unbinding events between the two freely diffusing DNA strands, and our measurements resolve multiple conformational states at elevated temperatures and low concentrations of NaCl.